<p class='jove_content'>We would like to acknowledge Mr. Ryohei Suganuma and Ms. Sakie Tachibana who helped perform the research. This study was supported in part by the JSPS KAKENHI Grant Numbers 15K20664, 24500848, and 21500405. This study was also funded in part by the MEXT/JST Tenure Track Promotion Program. A part of this study was based on the Japanese Unexamined Patent Application Publication No. 2011-169881 and the Japanese Patent No. 5708911.</p>

<p class="jove_content">注意:所述的装置，包括分析的方法，是通过日本未审查专利申请公开号2011-169881和日本专利5708911.本研究，包括与人受试者在实验的协议所覆盖，是经医学金泽大学的伦理委员会（＃553-1）。 </p><p class="jove_title"> 1.先决条件汗渍监测装置</p><p class="jove_content">注:第一次使用前一次执行这些步骤。 </p><ol><li>在计算机<sup>27</sup>上安装的通用串行总线（USB）-serial端口转换接口驱动程序。如果驱动程序已经安装，请跳过此步骤。 </li><li>通过USB数据线连接USB串口转换接口到计算机。等待自动安装驱动程序（如有）。 </li><li>设置转换接口的参数，并检查串口的ID号如下。 <ol><li>打开设备管理器，然后选择[查看]→[按类型的设备。 </li><li>找到"端口（COM和LPT）"的标题，并展开部分，找到包含"USB CP210X转UART桥"列表的标题。 </li><li>在"USB CP210X转UART桥接"标题记忆端口（ <em>例如，"COM5"）</em>的ID号。 </li><li>双击"USB CP210X到UART桥"，打开"端口设置"​​选项卡。 </li><li>设置方法如下参数:"每秒位数"= 9600"，数据位"= 8，"平价"="无"，"停止位"= 1，"流量控制"="无"。 </li><li>点击"确定"按钮关闭该窗口，并关闭设备管理器。 </li></ol></li></ol><p class="jove_title"> 2.汗渍监测设备安装</p><p class="jove_content">注:使用设备之前，如下设置记录设置。重复这些步骤为每个设备，如果多个设备使用。 </p><ol><li>确保电池没有在排汗监控装置插入。 </li><li>将USB串行端口转换接口到容器的白色连接在排汗监视装置的顶部。 </li><li>执行排汗的录音软件，其次是如下设置设备参数。 <ol><li>打开"设置"选项卡。 </li><li>将"COM"号到串行端口的ID号（见步骤1.3.3）。 </li><li>点击"确认连接"按钮。检查"......连接"出现的消息。 </li><li>在"数据文件文件夹"设置中，选择驱动器并选择排汗数据将被保存的文件夹。要选择子文件夹，双击文件夹打开。 </li><li>设置"的孔的数量"为"4"。 </li></ol></li><li>打开"测量及拍摄"标签，并在"时间间隔"设置为所需的采样时间。 </li><li>插入棉絮ERY的汗水监控设备。 </li><li>装满干硅胶装置（颜色应该是蓝色或绿色，如果颜色指示灯可用），并盖上盖子。如果盖不完全关闭，减少硅胶的量。 </li><li>点击排汗录音软件"开始记录现在"按钮。 <br />注意:由于出汗记录刚断开之后开始，排汗监控装置可保持连接直到监视将要开始。 </li></ol><p class="jove_title"> 3.设置为交感神经皮肤反应的测量（SSR） </p><p class="jove_content">注意:这些步骤的目的是监测交感神经活动为掌SSR，并且不一定需要排汗监测本身。 SSR是根据交感神经兴奋等刺激不安和浓度<sup>28,29</sup>皮肤的潜在变化。 </p><ol><li>洁净其中要被记录的SSR的皮肤用酒精棉签。 </li><li>把阳极，阴极和接地电极上的手掌，手背，和手腕，分别由一个电极浆料的装置。修正了医用胶带的电极。 </li><li>灵敏度= 1 mV / V的高截止滤波器（"HI CUT"）= 3千赫和低切滤波器（"LO CUT"）= 0.5:通过转动放大器的相应旋钮如下设置仪表放大器的条件赫兹。 </li><li>执行SSR的记录软件，及通过点击软件"开始测量"按钮来启动，在200赫兹的采样率记录。 </li></ol><p class="jove_title"> 4.排汗记录</p><ol><li>放的医用双面胶带的排汗监视装置的底部。把磁带时，确保测量窗口（在设备底部<em>，即</em>四个孔）不受阻。 </li><li>从便利着想USB串行端口断开汗水监控装置rsion接口。断开后，立即观察汗水监控自动开始。确保LED灯闪烁。 </li><li>除去医疗双面胶带的剥离衬垫，并把排汗监视装置上，其中排汗是要监控的皮肤。 </li><li>等待水蒸汽扩散的稳定化10分钟。 <br />注意:虽然这个过程不能被监视，以前的研究已经证实，在等待10分钟是足够的稳定监测<sup>26。</sup> </li><li>开始考试（ <em>如</em>交感神经活性测试）。 </li><li>考试结束后，去除皮肤排汗监控设备。要停止录制SSR，点击"停止测量"按钮，在SSR录音软件，并从皮肤移除所有电极。 </li></ol><p class="jove_title"> 5.汗渍分析</p><ol><li>汗监控设备连接到USB串口转换interfaCE（如在步骤2.2）。 </li><li>执行排汗监控软件。 </li><li>打开"设置"选项卡，然后点击"确认连接"按钮。 </li><li>打开"测量与REC"选项卡，并单击"下载"按钮，保存在指定文件夹的设备的原始数据（见步骤2.3.4）。 </li><li>如下执行排汗分析。 <ol><li>打开"分析"选项卡，然后点击"读取数据文件"。遵守"打开文件"对话框弹出。选择在步骤5.4保存的文件，然后单击"打开"按钮。 <br />注:该软件会自动执行基于已公布的方法<sup>26</sup>排汗分析，其结果会显示在屏幕上。与此同时，排汗数据作为逗号分隔值格式将被保存在同一文件夹。 </li></ol></li></ol>

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<p class='jove_content'>The author Fukuoka Masakazu is the president of the Rousette Strategy Inc., where the developed device was assembled. No financial support was received from either Fukuoka Masakazu or the Rousette Strategy Inc.</p>

<p class="jove_content">本文的目的是介绍使用一种新型的，无线的汗水监控装置。由于最近的工程的进步，更精确，便于手柄方法颞排汗监测已经提出;通风室方法<sup>24,25</sup>和蒸气压扩散法<sup>23</sup>是代表性实例。然而，通风室方法需要使用干燥的氮气或干燥剂以产生干燥气氛的泵，因此，外部的倾向变大。蒸气压扩散方法能在一个小的外部通过，尽管开放室系统可以通过外部大气在很大程度上影响，所述封闭室系统具有任水蒸气饱和的问题（该室填充有饱和水蒸气）或水蒸汽冷凝器的相当大的功率消耗（ <em>例如</em> ，珀耳帖装置）。 </p><p class="jove_content">为了应对这种情况，我们最近开发了一种新的无线设备的汗水监控<sup>26。</sup>在该装置中，从皮肤中的水蒸汽可以通过的干燥剂被捕获，从而使一恒定但自然流动。中的水蒸汽行进的过程中，T /相对湿度传感器捕获水蒸气如在温度和相对湿度的变化的流动。通过计算下菲克定律这样的变化，我们可以估算排汗量（毫克/厘米<sup>2</sup> /分钟）与&lt;5％的误差，相对于传统的通风室法<sup>26</sup>的时间的变化。所开发的装置可用于，例如，监视精神压力（ <strong>图2），</strong>热出汗，最终排汗有关的失调以更容易的方式。 </p><p class="jove_content">所开发的设备很容易处理，所以需要考虑几点。然而，如果硅胶未干排汗测量将失败。因此，在实验之前，0;审查员应该确保硅胶完全干燥（ <em>即</em>颜色为蓝色）。先前的研究估计测量长于4小时的最长期限不改变硅胶<sup>26。</sup>重新性质硅胶，干它在干燥炉直至颜色变蓝。传统的微波炉也是有用的。如果该装置的附件不充分排汗测量也将失败。我们建议一个"环形"双面胶带的使用。 </p><p class="jove_content">尽管如此，开发的设备有一个限制。因为微妙计算和干燥剂吸收的极限，排汗量的误差，应考虑，特别是在排汗的更高的水平。虽然我们已经证实了错误率作为是相对于常规方法<sup>26</sup> &lt;5％时，计算出的汗值的绝对值应谨慎处理。 </p><p class="jove_content">由于该装置的体积小，操作简单，而且无线设计，不受限的条件下将多排汗监测是可能的。正如<strong>图3</strong>所示，排汗的不同时间轮廓可在日常生活中的条件的皮肤（ <em>即</em>手掌和前胸部）的不同的位置进行检测（ <em>例如</em> ，聊天，吃的食物，驾驶汽车，购物<em>等</em> ）。 。的装置，因此，可能被用于异常出汗的同时检测从心理和热调节系统故障衍生两者。例如，如果左和右鞋底之间的不平衡出汗是待检测在糖尿病周围神经系统的失调可能被检测到。我们现在的住院患者规划排汗型材观察性研究作为临床实验。 </p>

<p class="jove_content">人体出汗，一般称为"出汗"，不只是对于体温<sup>1</sup>的机构，但它也与某些种类的疾病。异常排汗的病因是广泛的，包括:中暑，高-或甲状腺机能减退<sup>2，</sup>脑梗塞<sup>3，</sup>糖尿病<sup>4，</sup>自主神经功能异常<sup>5，</sup>绝经（称为"潮热<sup>"）6，</sup>囊性纤维化<sup>7，</sup>帕金森氏病<sup>8，</sup>和社会焦虑症<sup>9。</sup>在排汗有关的疾病的数量的光，它已被认为是有益的并监控排汗率此类疾病的早期诊断或预测（ <em>例如，</em>预防中暑的）是一个普遍存在的方式<sup>10。</sup> </p><p class="jove_content">迄今为止，只有对排汗监测装置的一个小数目已经被提出。在早期，皮肤电导和相对湿度分别用于间接我排汗<sup>11,12</sup>的量的ndices。最近，数种对排汗监测柔性的，可穿戴的传感器已被提出<sup>13-19，</sup>尽管它们旨在用于汗水电解质的分析，而不是量或排汗的时间模式。水蒸汽扩散的计算已被用于从皮肤<sup>20-23</sup>监测水交换的更定量的方法。然而，这需要:（1）假设的外气氛仍然和常数<sup>20，（2）</sup>足以灵敏度来检测水蒸气<sup>21,22，</sup>或（3）的冷却剂（ <em>如</em> ，珀耳帖装置，其消耗的自然流动电力的大量）冷凝水蒸汽液体<sup>23;</sup>因此，它们可能难以每日和长期监测。作为一种替代，一个通风室方法被开发<sup>20,24,25。</sup>在通风室的方法，干燥的氮气或除湿的空气在邻近于从在从皮肤蒸发的水蒸汽的氮气罐或泵和气体皮肤的小室渗入被收集。从皮肤的水蒸汽的量可以从在出口和入口气体的湿度的差来计算。虽然这种方法可以估算排汗量非常精确，氮气罐或机械泵是通常大到足以妨碍日常监控。 </p><p class="jove_content">为了解决这些缺点，我们最近开发了排汗监测的新型设备，其中有干燥剂驱动强制水蒸汽流的密闭室，使敏感和长期监测<sup>26。</sup>此装置由与记录的微处理器，和硅胶（ <strong>图1）</strong>的圆筒形塑料外壳，温度/相对湿度（T / RH）传感器。原则上，外部大气不应该与水蒸汽流，和一个冷却剂或ventilatin干扰克腔是不需要的。排汗配置文件可以通过使用电子表格软件<sup>26</sup>求解方程来获得。先前的研究已经显示只有发达装置的原理，并省略了如何使用，因为空间限制的设备的详细方法。 </p><p class="jove_content">本文的目的，因此，是显示如何使用显影装置排汗监测，通过显示交感神经活性试验，例如，在应激诱导的手掌出汗的记录的详细方法。 </p>

<table><tbody><tr><td>Required for perspiration monitoring</td><td></td><td></td><td></td></tr><tr><td>Perspiration monitoring device</td><td>Rousette Strategy Inc.</td><td>SNT-200</td><td></td></tr><tr><td>USB-serial port conversion interface</td><td>Rousette Strategy Inc.</td><td>UUI-200</td><td></td></tr><tr><td>Perspiration recording software</td><td>Rousette Strategy Inc.</td><td>TED99</td><td></td></tr><tr><td>Silica gel</td><td>Wako Pure Chemical Industries Ltd.</td><td>194-16665</td><td>Type A silica gel should be used.</td></tr><tr><td>Medical double-sided tape</td><td>3M</td><td>2181</td><td>Medical grade is recommended because of the attachment to the skin.</td></tr><tr><td>Computer</td><td></td><td></td><td>Requires Windows operating system.</td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Required for the monitoring of sympathetic skin response&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Instrumentation amplifier</td><td>Nihon Kohden Corp.</td><td>AB-611J</td><td></td></tr><tr><td>Amplifier chassis</td><td>Nihon Kohden Corp.</td><td>MEG-6108</td><td></td></tr><tr><td>Input box</td><td>Nihon Kohden Corp.</td><td>JB-610B</td><td></td></tr><tr><td>Alcohol swab</td><td>Suzuran Sanitary Goods Co., Ltd.</td><td>4545766050846</td><td></td></tr><tr><td>Electrodes</td><td>Nihon Kohden Corp.</td><td>NE-114A</td><td></td></tr><tr><td>Electrode paste</td><td>Nihon Kohden Corp.</td><td>Z-401CE</td><td></td></tr><tr><td>Medical tape</td><td>Nichiban Co., Ltd.</td><td>SG257</td><td></td></tr><tr><td>Analog signal interface</td><td>Micro Science K.K.</td><td>C BOX-014</td><td></td></tr><tr><td>Analog-to-digital converter</td><td>Micro Science K.K.</td><td>ADM-686PCI</td><td></td></tr><tr><td>SSR recording software</td><td>Matsuyama Advance Co., Ltd.</td><td>LaBDAQ2000</td><td></td></tr></tbody></table>

a detailed protocol for perspiration monitoring using a novel, small, wireless device

<p class="jove_content">排汗监测可用于检测某些疾病，如体温调节和精神障碍，尤其是当患者不知道这样的病症或有困难表达他们的症状。直到现在，排汗监测几个设备已被开发;然而，这种设备往往具有相对大的外部，相当大的功耗，和/或灵敏度以下。 </p><p class="jove_content">最近，我们制定了汗水监控的小型无线设备。该装置由一个温度/相对湿度（T / RH）传感器，电池驱动的小的数据记录器，且将硅胶用作在一个小的圆柱形外部的干燥剂。为T /相对湿度传感器被放置在检测窗口（通过它从皮肤水蒸气进入），并在硅胶之间。排汗监视装置的基本原理是基于扩散的Fick定律，这意味着水蒸汽线FROM皮肤到硅胶（ <em>即</em>经皮水分损失和汗）可通过在在T /相对湿度传感器的湿度变化被捕获。另外，基线减法方法获得通过区分汗渍和经皮水分流失。 </p><p class="jove_content">如在先前的报告中所示，显影设备可以监控在主体的以容易，无线方式任何网站的汗水。然而，如何使用该装置的详细方法尚未公开。在这篇文章中，因此，我们想显示如何使用设备的汗水监控，通过展示与交感神经皮肤反应监测作为一个例子交感神经活性试验点逐点教程。 </p>

<p class="jove_content" fo:keep-together.within-page="1">使用这种新型装置排汗监视（ <strong>图1）</strong>和菲克依法计算，颞排汗配置文件可以在一个简单的，无线的方式来获得。 <strong>图2</strong>示出了交感活性试验过程中的无线排汗监测代表性数据。在实验中，对于排汗监视的装置中，与用于交感神经皮肤反应（SSR）监控电极一起被连接到被检者的手掌。对于交感神经活性测试，要求主体坐下来执行以下任务:（1）取一深吸气5次1分钟的间隔，和（2）做一个心算（ <em>例如</em> ，不断地从100减去7，或中的"Flash暗赞"，其中参与者总结了数字逐一显示在计算机屏幕上以后）唤起交感神经活性。排汗和SSR分别为SIM卡<html>在胁迫条件ultaneously记录。如深吸气和精神的计算结果，交感活性诱导的手掌出汗可以使用发达装置来测量。 <strong>图3</strong>示出了在日常活动中的多点测量的代表性数据。在手掌（情绪出汗）和前胸部（热出汗）排汗约1小时录音根据活动表现出不同的模式。 </p><p class="jove_content" fo:keep-together.within-page="1"><img alt="图1" src="/files/ftp_upload/54837/54837fig1.jpg" /><br /> <strong><strong>图</strong> 1:</strong> <strong>汗渍监控的新设备</strong> <strong>（A）</strong>含干硅胶设备的外观<strong>。</strong> <strong><strong>（B，C）</strong></strong>一个"环形"双面本研究及其附到设备使用的磁带。 <strong>（D）</strong>的设备到皮肤的附件。OM /文件/ ftp_upload / 54837 / 54837fig1large.jpg"目标="_空白"&gt;点击此处查看该图的放大版本。 </p><p class="jove_content" fo:keep-together.within-page="1"><img alt="图2" src="/files/ftp_upload/54837/54837fig2.jpg" /><br /> <strong>图2:</strong> <strong>排汗代表记录下交感神经活性测试</strong> <strong>（A）</strong>与交感神经皮肤反应（SSR）在手掌电极排汗监测设备的附件<strong>。</strong> （ <strong>二</strong> ）由于交感神经活性测试的结果，以响应交感神经活动观察SSR反应沿手掌出汗。 <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/54837/54837fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> </p><p class="jove_content" fo:keep-together.within-page="1"><img alt="图3" src="/files/ftp_upload/54837/54837fig3.jpg" /><br /> <strong>图3:</strong> <str翁&gt;汗渍的代表多点记录在日常活动根据身体的不同部位的排汗不同的模式;进行中的几项活动观测（ <em>例如</em> ，去（红线，在手掌的蓝线，在前胸）下楼，开车，有一个午餐说话，购物）。 <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/54837/54837fig3large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> </p>

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A Detailed Protocol for Perspiration Monitoring Using a Novel, Small, Wireless Device

<p class='jove_content'>Recently, we developed a small wireless device for perspiration monitoring. In this article, we present detailed protocols on how to use the device for perspiration monitoring with an example of the sympathetic activity test.</p>

详细的汗渍监控协议使用一种新的，小的，无线设备

Perspiration monitoring can be utilized for the detection of certain diseases, such as thermoregulation and mental disorders, particularly when the ...

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7.8K 次观看.  Kanazawa University. Recently, we developed a small wireless device for perspiration monitoring. In this article, we present detailed protocols on how to use the device for perspiration monitoring with an example of the sympathetic activity test.

视频: A Detailed Protocol for Perspiration Monitoring Using a Novel, Small, Wireless Device

Thin-Layer Chromatography

<p>Source: Lara Al Hariri and&#160;Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Effects of Mobile Phase Composition on Compound Separation<button class="expand">Expand</button>
	<p>In this section of the lab, you will use TLC to compare how well pure hexane and a mixture of 60% hexane and 40% ethyl acetate can separate phenol, benzoic acid, and butyl phenyl ether by measuring the distance the compound traveled in each solvent.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-2">
		<div class="lab-step">Before starting the lab, put on a lab coat, safety glasses, and nitrile gloves. Note: Hexane and ethyl acetate are both volatile, toxic, and flammable, so always work with them in a fume hood. Change your gloves if you get solvent on them, as hexane and ethyl acetate will permeate nitrile gloves within minutes.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Now, obtain a paper towel and lay it on the benchtop. Carefully pick up a TLC plate using tweezers at the very end of the plate.<strong> Note: </strong>Always hold TLC plates by the edges or at the very top with tweezers to avoid damaging or contaminating the silica gel.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Look for chips or scratches in the silica gel and get a new plate if necessary. It&#39;s fine if there is a little chipping at only one end, since that can be the top.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Place the plate on the paper towel in your fume hood, and lay a metric ruler next to it. Use a graphite pencil to gently make a small mark on the silica gel ~1 cm from the top of the plate. Write &#8216;100&#8217; on the plate above the mark.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Next, gently mark the plate 1 cm above the bottom on both sides. Carefully trace a straight line between the bottom marks to make the starting line.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Then, add 3 evenly spaced small marks to the starting line with the outer marks at least 0.5 cm from the sides of the plate. <strong>Note:</strong> It&#39;s important for the silica gel to be undamaged here, so if you scratch it with the pencil, prepare a new plate.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Now, trace the outline of the TLC plate in your lab notebook and precisely copy the marks on the plate. Label the three marks as &#8216;phenol&#8217;, &#8216;benzoic acid&#8217;, and &#8216;butyl phenyl ether&#8217;. You may also want to label the marks on the plate itself.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Prepare a second TLC plate labeled &#8216;60/40&#8217; in the same way. Now, bring the labeled plates to the common bench and locate the 1 mg/mL solutions of phenol, benzoic acid, and butyl phenyl ether in ethanol.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Dip a clean capillary into one of the three solutions. Briefly and lightly dab the capillary squarely against the intersection between the starting line and the mark for that compound. You should spot twice for each compound.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Use the same capillary to spot the same solution on your second TLC plate. The spots should be no more than 2 mm in diameter. Then, discard the capillary and close the vial.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Spot the other two solutions on the plates, in the same way, using clean capillaries. Be careful not to cross-contaminate the solutions. <strong>Note</strong>: If a spot is very light or very small, wait for it to dry, and then spot the same solution on top of the dry spot. If the spot is still wet, capillary action could make it too wide and dilute.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Once you have made three spots on each plate, discard the capillaries and bring the plates back to your hood. Keep the plates lying flat while they dry.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Now, label a 50-mL jar &#8216;100% hexane&#8217; and bring the jar, its cap, and a 10-mL graduated cylinder to the solvent hood.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Measure 2 &#8211; 3 mL of pure hexane with your graduated cylinder and pour it into the jar to fill it to a depth of 0.62 &#8211; 0.7 cm. Cap the bottle and jar and return to your fume hood.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Label a second 50-mL jar &#8216;60% hexane, 40% ethyl acetate&#8217; and bring it and a clean graduated cylinder to the solvent hood. Measure 2 &#8211; 3 mL of the 60/40 mixture into the jar and return to your fume hood.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Stand the plates next to the jars to compare the relative position of the solvent and the spots. The solvent level should be below the spots for each plate.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Then, obtain three pieces of filter paper, put a filter paper upright against the wall in each jar, and then cap the jars tightly.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Initial each plate above the mark so you can identify them later. Confirm that the filter papers in the jars have become saturated with solvent and that the spots on the plates are completely dry.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Now, open the 100% hexane jar and use tweezers to gently place the 100 plate in the jar, keeping the plate level with the solvent surface as it enters the solvent. Close the jar tightly, being careful not to jostle the plate.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Leave the jar still as the solvent travels up the plate. Development in pure hexane usually takes about 7 &#8211; 10 min. Keep an eye on the plate to make sure that the solvent doesn&#39;t reach the top.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">When the pure hexane solvent front is about 1 cm from the top of the plate, retrieve it using tweezers. Lay it on the paper towel with the silica gel facing up and quickly mark the solvent front with a line and pencil across the plate. Leave the plate lying flat as the solvent evaporates.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Place the other plate in the 60/40 eluent in the same way. Wait until the solvent front of the 60/40 plate is about 1 cm from the top, and then retrieve it and quickly mark the solvent front in the same way.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">Once the 100% hexane plate is completely dry, pick it up with tweezers and bring it and a pencil to the UV lamp on the common bench.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">Place the plate under the lamp and illuminate it with UV light. The plate will glow green because of a fluorescent marker in the silica gel layer. The dark spots are the compounds.</div>
		</li>
		<li data-sub-note-item="1-26">
		<div class="lab-step">Carefully outline every spot in pencil, even if they haven&#39;t moved very far.</div>
		</li>
		<li data-sub-note-item="1-27">
		<div class="lab-step">Then, turn off the lamp and bring your plate to the iodine development hood. Open the iodine chamber. Use tweezers to gently place the plate upright in the iodine chamber, and then cover the chamber again.</div>
		</li>
		<li data-sub-note-item="1-28">
		<div class="lab-step">Wait 3 &#8211; 4 min for the iodine vapor to stay in the spots. Then, retrieve the plate with tweezers, close the chamber, and outline the brown and yellow spots on the plate. These spots will fade, so mark them quickly.</div>
		</li>
		<li data-sub-note-item="1-29">
		<div class="lab-step">Visualize the dry 60/40 plate under UV light and then with iodine vapor in the same way.<strong> Note: </strong>To avoid side reactions, always check plates under UV light before exposing them to iodine.</div>
		</li>
		<li data-sub-note-item="1-30">
		<div class="lab-step">Now, precisely copy the spots and the solvent fronts onto the corresponding drawings of the plates in your lab notebook. For each plate, measure and record the height of the solvent front relative to the starting line.</div>
		</li>
		<li data-sub-note-item="1-31">
		<div class="lab-step">Lastly, measure the distance between the center of each spot and its starting line, and record it in your lab notebook. You can now move on to the next part of the lab.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Unknown Compound Identification<button class="expand">Expand</button>
	<p>In the second half of the lab, you&#39;ll use TLC to find out what&#39;s in an unknown analgesic. It could contain one or more of these compounds: aspirin, caffeine, and acetaminophen. These compounds are highly polar, so you&#39;ll use a premade mixture of 90% ethyl acetate and 10% hexane as the eluent.</p>
	<p>You&#39;ll run the three reference compounds and the unknown all on the same plate. Later, you&#39;ll use the Rf values of the reference compounds to identify the unknown. First, double-check which unknown material you were assigned to analyze before starting.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-3">
		<div class="lab-step">Now, lay a clean paper towel in the hood and obtain a new TLC plate. Prepare the top mark and the starting line the same way as before. Make four evenly spaced ticks on the plate, making sure that the outer marks are at least 0.5 cm away from the edges.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Draw an exact copy of the plate in your lab notebook and label the tick marks as &#8216;aspirin&#8217;, &#8216;acetaminophen&#8217;, &#8216;caffeine&#8217;, and &#8216;unknown&#8217;.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Now, bring your plate to the common bench. Spot solutions of aspirin, acetaminophen, caffeine, and the unknown that you were assigned on the appropriate marks using a clean capillary for each solution. <strong>Note: </strong>When you are spotting the unknown solution, don&#39;t dip the capillary too far into the solution vial to avoid clogging your capillary with insoluble material from the unknown substance.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Discard the capillaries and close the vials before bringing the plate back to your fume hood. Place the plate on a paper towel to finish drying.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Next, label a clean 50-mL screw-top jar &#8216;90% ethyl acetate, 10% hexane&#8217;, and bring it in a clean graduated cylinder to the solvent hood.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Place 2 &#8211; 3 mL of the 90/10 solution in the jar and return to your fume hood. Confirm that the solvent level will be below the spots on the plate. Then, place a clean filter paper upright in the jar and close it tightly.</div>
		</li>
		<li data-sub-note-item="2-9">
		<div class="lab-step">Once the TLC plate is dry and the filter paper is saturated, carefully place the plate in the solvent. <strong>Note:</strong> It&#39;s essential to hold the plate level when you do this. If the solvent front is diagonal, the solvent distance traveled will be different for each spot, making it impossible to visually compare the unknown to the reference spots.</div>
		</li>
		<li data-sub-note-item="2-10">
		<div class="lab-step">Wait for the solvent front to reach 1 cm from the top of the plate. Then, retrieve the plate, mark it solvent front, and let it dry while lying flat.</div>
		</li>
		<li data-sub-note-item="2-11">
		<div class="lab-step">Once the plate is dry, visualize it with UV light and in the iodine chamber, and outline the spots in pencil.</div>
		</li>
		<li data-sub-note-item="2-12">
		<div class="lab-step">The unknown material could be a mixture of compounds, so look carefully for spots in line with all three reference spots.</div>
		</li>
		<li data-sub-note-item="2-13">
		<div class="lab-step">Then, precisely copy the spots onto the drawing of the plate in your lab notebook. Measure and record the height of the solvent front and the spots relative to the starting line.</div>
		</li>
		<li data-sub-note-item="2-14">
		<div class="lab-step">When you are finished, retrieve the solvent-saturated filter papers from the jars and let them dry in the hood.</div>
		</li>
		<li data-sub-note-item="2-15">
		<div class="lab-step">Pour leftover solvents into the standard organic waste, wash your glassware following your lab&#39;s usual methods, and put away your lab equipment.</div>
		</li>
		<li data-sub-note-item="2-16">
		<div class="lab-step">Throw out used TLC plates in the lab trash or with glass waste, depending on the backing material.</div>
		</li>
		<li data-sub-note-item="2-17">
		<div class="lab-step">Lastly, once the filters are dry, throw them out along with any remaining trash.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="3" data-parent-collapse="">Results<button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="3-1">
		<div class="lab-step">Calculate the R<sub>f</sub> values for phenol, benzoic acid, and butyl phenyl ether eluted with 100% hexane. For each compound on the TLC plate, measure the distance from the starting line to the center of its spot. Then, divide this value by the distance from the starting line to the solvent front.</div>
		</li>
		<li data-sub-note-item="3-2">
		<div class="lab-step">Only butyl phenyl ether moved a measurable distance from the starting line, which is consistent with it being the least polar. For effective separation, the R<sub>f</sub> values should differ by 0.3 &#8211; 0.7. Thus, we can infer that phenol and benzoic acid are too polar to be separated effectively by an apolar solvent like pure hexane.</div>
		</li>
		<li data-sub-note-item="3-3">
		<div class="lab-step">Calculate the R<sub>f</sub> values for the plate that you ran in a 60/40 mixture of hexane and ethyl acetate. Ethyl acetate is a moderately polar solvent, so the compounds traveled farther and are spaced farther apart on the plate.</div>
		</li>
		<li data-sub-note-item="3-4">
		<div class="lab-step">The separation order shows that benzoic acid, the most polar compound, had the highest affinity for silica gel, whereas butyl phenyl ether, the least polar compound, had the lowest affinity for silica gel. This is consistent with the assumption that less polar compounds travel farther on polar stationary phases.</div>
		</li>
		<li data-sub-note-item="3-5">
		<div class="lab-step">Look at your third plate and calculate the R<sub>f</sub> values for aspirin, acetaminophen, and caffeine. Caffeine, the most polar complex of the three, traveled the least. Acetaminophen traveled the second farthest, while aspirin, the least polar, traveled the most.</div>
		</li>
		<li data-sub-note-item="3-6">
		<div class="lab-step">Finally, identify the compounds in your unknown material by comparing its spot or spots to the three reference spots.</div>
		</li>
	</ul>
	</li>
</ol>

Thin-Layer Chromatography: Experimental Setup and Separation - Procedure

薄层色谱

Source: Lara Al Hariri and&#160;Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA

	Effects of Mobile Phase Composition on Compound ...

教育

JoVE Lab Manual

化学

Lab Manual Sub Articles

Temperature Dependence

<p>Source: Smaa Koraym at Johns Hopkins University, MD, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Temperature Dependent Decomposition of Hydrogen Peroxide<button class="expand">Expand</button>
	<p><em>We suggest that students work in pairs for this experiment. Equipment controls may vary.</em></p>
	<p>In this lab, you&#39;ll perform a decomposition reaction where a single compound breaks down into two or more simpler products. You will observe the decomposition of hydrogen peroxide into water and oxygen. This decomposition happens very slowly, so you will use iron (III) nitrate as a catalyst to lower the activation energy.</p>
	<p>During this process, iron undergoes a redox reaction and then returns to its starting oxidation state. You will be able to see this as a color change in your solution during the reaction. You&#39;ll perform the same reaction at four different temperatures and track the rate of the reaction by recording the pressure inside the flask. This way you can measure how quickly oxygen was produced in each experiment. You&#39;ll use this to calculate the reaction&#39;s activation energy.</p>
	<p><strong>Table 1. Estimate the apparent activation energy for the decompostion of hydrogen peroxide</strong></p>
	<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
		<tbody>
			<tr>
				<td><strong>Trial&#160;</strong></td>
				<td><strong>Temperature (&#8451;)</strong></td>
				<td><strong>&#916;P (kPa/s)</strong></td>
				<td><strong>1/T&#160;</strong></td>
				<td><strong>ln (&#916;P)</strong></td>
			</tr>
			<tr>
				<td>1</td>
				<td></td>
				<td></td>
				<td></td>
				<td></td>
			</tr>
			<tr>
				<td>2</td>
				<td></td>
				<td></td>
				<td></td>
				<td></td>
			</tr>
			<tr>
				<td>3</td>
				<td></td>
				<td></td>
				<td></td>
				<td></td>
			</tr>
			<tr>
				<td>4</td>
				<td></td>
				<td></td>
				<td></td>
				<td></td>
			</tr>
		</tbody>
	</table>
	<p><a href="/CDNSource/labs/51/Table_1._Estimate_the_apparent_activation_energy_of.xlsx" target="_blank">Click Here to download Table 1</a> &#160;</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-1">
		<div class="lab-step">Before starting this experiment, put on a lab coat, safety glasses, and nitrile gloves.</div>
		</li>
		<li data-sub-note-item="1-2">
		<div class="lab-step">Ensure that your hot plate is off and then place a 600-mL beaker on the hot plate.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Connect vacuum tubing to the barbed sidearm of a 125-mL B&#252;chner filter flask, and carefully clamp the filter flask in the 600-mL beaker so that the sidearm is just above the top of the beaker.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Fill a 400-mL beaker with deionized water., and pour the water into the 600-mL beaker until the water level is about 2&#8211;3 cm below the side arm.<br />
		<strong>NOTE</strong>: Make sure that the water is not able to get into the flask or vacuum line.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Immerse the thermometer in the water, clamping it in place so that the end is in contact with the outer wall of the flask. Ensure that you can read the current temperature, as well as the 40, 60, and 80 &#176;C marks.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Make sure that each hole of the 2-hole adapter is fitted with a tapered locking adapter. Check that all the adapters are firmly seated, since any air that escapes around them will affect your data.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Lock a 2-way stopcock into one of the stopper adapters. Then, lock one end of the flexible tubing into the second adapter with the other end into the connector of the gas pressure sensor.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Turn on the data acquisition device for the gas pressure sensor and ensure that the pressure is displayed in kPa.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Set the acquisition rate to two samples per second and the duration to 300 s. Then, display the pressure in real-time.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Label a 400-mL beaker as &#8216;waste&#8217;, a 50-mL beaker as &#8216;0.5 M Fe(NO<sub>3</sub>)<sub>3</sub>&#8217;, and a 100-mL beaker as &#8216;3% w/w hydrogen peroxide&#8217;.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Place a few paper towels on the work surface as a clean area for glassware that you will reuse. Keep a supply of paper towels on hand for later.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Then, bring the 50-mL and 100-mL beakers to the stock solution area. Pour about 30 mL of 0.5 M Fe(NO<sub>3</sub>)<sub>3</sub> in the 50-mL beaker and 100 mL of 3% w/w hydrogen peroxide in the 100-mL beaker.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Back at your workspace, setup a 20-mL volumetric pipette and fill it to the mark with 3% w/w hydrogen peroxide. Dispense the hydrogen peroxide into the filter flask and set the volumetric pipette aside.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Adjust the thermometer as needed so that it contacts the flask below the hydrogen peroxide solution level.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Fit the rubber stopper into the mouth of the filter flask, being careful not to loosen the connections to the sensor and the 2-way stopcock.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Check that the 2-way stop is closed. Open the vacuum line and monitor the pressure as it decreases. This will seal the stopper in the flask. Once the pressure reaches 10 kPa, close the vacuum.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Monitor the pressure for at least 1 min to confirm there are no slow leaks.<br />
		<strong>NOTE</strong>: If the pressure immediately starts rapidly increasing, there is a leak in your setup, so tighten the connections and try again until the pressure holds at 10 kPa when the vacuum line is closed.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Draw 5 mL of 0.5 M Fe(NO<sub>3</sub>)<sub>3</sub> into a 20-mL syringe. Expel all air from the syringe so that it only contains the solution.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Lock the syringe into the top of the 2-way stopcock. You are now ready to start the room temperature trial, so record the water temperature in your lab notebook.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Start acquiring gas pressure data. Allow the device to record data for about 15 s, then open the stopcock and quickly close it once all of the Fe(NO<sub>3</sub>)<sub>3</sub> has entered the flask. The observed increase in pressure is from the evolution of oxygen gas produced by the decomposition of hydrogen peroxide.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">Once the data collection finishes, save your data. Then, disconnect the syringe and open the stopcock to vent the flask.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Take out the rubber stopper, carefully remove the thermometer from the clamp and the flask from the beaker, and disconnect the vacuum tubing from the filter flask.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">Empty the flask into the waste beaker. Try not to get liquid in the side arm. Dry the outside of the flask with paper towels.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">Rinse the interior of the flask with deionized water and pour the rinse into the waste beaker. If any liquid gets into the side arm, remove it with paper towels.</div>
		</li>
		<li data-sub-note-item="1-26">
		<div class="lab-step">Reconnect the flask to the vacuum line and clamp it in the 600-mL beaker in contact with the thermometer.</div>
		</li>
		<li data-sub-note-item="1-27">
		<div class="lab-step">Turn on the hotplate and heat the water around the flask until the thermometer reads 80 &#176;C. Then, turn off the heat.</div>
		</li>
		<li data-sub-note-item="1-28">
		<div class="lab-step">Then, add 20 mL of 3% w/w hydrogen peroxide to the flask.</div>
		</li>
		<li data-sub-note-item="1-29">
		<div class="lab-step">Dry the stopper with paper towels. Do this after each trial to ensure that the stopper has a snug fit in the neck of the beaker and fit the stopper in the flask.</div>
		</li>
		<li data-sub-note-item="1-30">
		<div class="lab-step">Check that the stopcock is closed and evacuate the flask to about 10 kPa. Then, close the vacuum and confirm that there are no leaks.</div>
		</li>
		<li data-sub-note-item="1-31">
		<div class="lab-step">Draw 5 mL Fe(NO<sub>3</sub>)<sub>3</sub> solution into the syringe, expel the air from the syringe, and connect it to the stopcock.</div>
		</li>
		<li data-sub-note-item="1-32">
		<div class="lab-step">Record the temperature shown on the thermometer in your lab notebook, then, start collecting data.</div>
		</li>
		<li data-sub-note-item="1-33">
		<div class="lab-step">Wait about 15 s and introduce the Fe(NO<sub>3</sub>)<sub>3</sub> solution in the same way as before.<br />
		<strong>NOTE:</strong> As the pressure approaches 150 kPa, the stopper may pop off!</div>
		</li>
		<li data-sub-note-item="1-34">
		<div class="lab-step">After data collection finishes, save the data, vent and clean the filter flask, and set up for the third trial.</div>
		</li>
		<li data-sub-note-item="1-35">
		<div class="lab-step">Fill the 400-mL beaker with ice and add some to cool the water to about 60 &#176;C.</div>
		</li>
		<li data-sub-note-item="1-36">
		<div class="lab-step">Perform the third trial in the same way as before. Remember to dry the stopper and the inside of the flask and to record the temperature prior to data collection.</div>
		</li>
		<li data-sub-note-item="1-37">
		<div class="lab-step">After the data is collected for that trial, cool the water to about 40 &#176;C and perform the fourth trial.</div>
		</li>
		<li data-sub-note-item="1-38">
		<div class="lab-step">Once you have finished all four trials, empty the filter flask and rinse it into the waste beaker one last time.</div>
		</li>
		<li data-sub-note-item="1-39">
		<div class="lab-step">Dispose of any excess 0.5 M Fe(NO<sub>3</sub>)<sub>3</sub> and the contents of the waste beaker in a container labeled for aqueous iron waste.</div>
		</li>
		<li data-sub-note-item="1-40">
		<div class="lab-step">Then, disassemble the apparatus and pour the leftover ice, water, and hydrogen peroxide in the sink. Wash your glassware following your lab&#39;s standard protocol.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="1" data-parent-collapse="">Results<button class="expand">Expand</button>
	<p>The decomposition of hydrogen peroxide with iron is a complex, multi-step process that we can&#39;t easily describe in a single equation. However, we can estimate the apparent activation energy from the rate of oxygen production and compare it to the apparent activation energy of the un-catalyzed process.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-1">
		<div class="lab-step">Find the rate of pressure change, which is directly proportional to the rate of oxygen production. For each experiment, make a plot of pressure with respect to time and find the point where the reaction started.</div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Identify the maximum pressure attained and determine the slope between the two points.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">Once you&#39;ve determined the slopes and the corresponding temperatures in Kelvin for all of the temperatures, use the Arrhenius equation to estimate the apparent activation energy of this reaction.</div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Take the reciprocal of the temperatures in Kelvin and the natural log of the rate of change in pressure. Remember that the rate constant k is essentially equal to the change in pressure.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Make an Arrhenius plot and find the slope of the line.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">The slope is equal to the negative activation energy over the universal gas constant, so multiply the slope by the negative universal gas constant to get the apparent activation energy of the iron catalyzed decomposition reaction. You&#39;ll see a value in the range of 35&#8211;60 kJ/mol because the iron catalyst made the decomposition take less energy. The apparent activation energy of the uncatalyzed decomposition of hydrogen peroxide is around 78 &#8211; 88 kJ/mol.</div>
		</li>
	</ul>
	</li>
</ol>

Temperature Dependence and Arrhenius Equation - Procedure

温度依赖性

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Temperature Dependent Decomposition of Hydrogen PeroxideExpand
	We suggest that students work ...

Galvanic Cells

Galvanic Cells: Construction and Reduction Potential Measurement - Procedure

原电池

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Constructing a Lead-Copper Galvanic CellExpand
	In this experiment, you will construct a ...

Electrolytic Cells

<p>Source: Smaa Koraym at Johns Hopkins University, MD, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Electrolytic Cells<button class="expand">Expand</button>
	<p>In this experiment, you will be assembling an electrolytic cell to perform electroplating. An electrolytic cell contains an anode and cathode connected by a power source, which drives the nonspontaneous redox reaction in the cell. When the anode material is oxidized, the ions travel to the cathode, where they are reduced and plated.</p>
	<p>In the case of this experiment, the electrolytic cell contains a copper anode and a brass key for the cathode. Oxidation of the anode creates copper(2+) ions, which are then reduced on the brass key, forming a thin plating of solid copper.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-3">
		<div class="lab-step">Put on gloves, safety goggles, and a lab apron, which must be worn at all times.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Obtain one 10-ohm resistor, one copper sheet electrode, one copper wire, and one piece of emery paper.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Use the emery paper to polish the brass key and the copper sheet. Rinse the key and the copper electrode with water. The brass key will be the cathode, and the copper sheet will be the anode.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Take one 50-mL beaker and a watch glass to the instructor&#39;s hood and obtain approximately 20 mL of acetone. Place the watch glass on top of the beaker to prevent evaporation and bring it back to your bench.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Label the other 50-mL beaker as &#39;organic waste&#39;.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Use a disposable pipette to rinse the copper electrode and key with acetone. Collect excess in the waste beaker. Place the key and copper electrode on a paper towel to dry.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Measure the initial masses of the key and copper electrode and record their values in your lab notebook.
		<h4><strong>Table 1: Moles of Cu Transferred</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td></td>
					<td style="text-align: center;"><strong>Mass of key (g) </strong></td>
					<td style="text-align: center;"><strong>Change in mass (g) </strong></td>
					<td style="text-align: center;"><strong>Moles Cu plated </strong></td>
					<td style="text-align: center;"><strong>Mass of Cu electrode (g) </strong></td>
					<td style="text-align: center;"><strong>Change in mass (g) </strong></td>
					<td style="text-align: center;"><strong>Moles Cu lost </strong></td>
				</tr>
				<tr>
					<td style="text-align: center;">0 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">5 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">1<sup>st</sup> 30 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">2<sup>nd</sup> 30 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www-jove-com.bdigitaluss.remotexs.co/CDNSource/lm/labs/53/Table_1._Moles_of_Cu_Transferred.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Set up the electrolytic cell. Use one electrical wire with alligator clips to connect the negative terminal on the battery to the current probe. Wrap the 10-ohm resistor around the other end of the current probe.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Use another wire to connect the positive terminal on the battery to the copper electrode.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Wrap the copper wire around the brass key and use an electrical wire to connect the resistor on the current probe to the copper wire on the brass key.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Obtain about 200 mL of concentrated copper sulfate in a 250-mL beaker. The amount does not need to be exact. Bring the beaker back to your bench and set it on the stir plate. Carefully, place a magnetic stir bar in the beaker and turn the stir setting on to high.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Connect the data acquisition system to the current probe and allow the data acquisition system to sense the probe. It should return a reading in amps. Change the rate to two scans per min and the duration to 5 min.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Place the brass key in the beaker. Hang it off the side of the beaker so that the key is almost completely submerged but does not touch the magnetic stir bar. <strong>Note: </strong>The copper wire should not be in the solution.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Place the copper electrode in the beaker, bending it so that it hangs over the edge of the beaker. Ensure that it is not touching the stir bar or the brass key.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Start the scan and let it collect data for 5 min. This will act as a test run to make sure plating occurs on the brass key.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">After the scan ends, remove the key and copper electrode. The copper plating on the brass key should be evident. If it is not visible, check your circuit to make sure that the battery is connected in the correct orientation.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Once you have completed a successful 5-min plating, disconnect the key and copper electrode from the wiring. Remove the copper wire from the key and rinse the key and copper electrode with water and then acetone. Lay them on a paper towel to dry.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Measure the masses of the key and the copper electrode and record them in your lab notebook.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Reconnect the key and copper electrode and place them back in the solution like before. Restart the run on the data acquisition system, making sure that the rate is set to two scans per min. With the duration set to 30 min, allow the electroplating process to run.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">After the scan is complete, remove the electrode and key from the solution, disconnect them from the wires, and rinse them with water and then acetone. Allow them to dry on a paper towel, then weigh them and record their masses in your notebook.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Reassemble the setup and repeat the electroplating for a second 30-min trial. When the scan is complete, remove the key and copper electrode, rinse them like before, and record their mass.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">Save the recorded data as a text file on a flash drive.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">To clean up, turn the stir setting off and remove the stir bar from the solution using forceps. Dispose of the acetone in the organic waste container provided by your instructor. The copper sulfate solution can be reused for future labs, so pour the concentrated copper sulfate back into the carboy.</div>
		</li>
		<li data-sub-note-item="1-26">
		<div class="lab-step">Rinse all of your glassware with water and return it to the instructor.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Results<button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="2-1">
		<div class="lab-step">First, calculate the total charge Q that flowed through the system during the different trials. One coulomb is the quantity of electricity flowing through a wire carrying 1 ampere of current in 1 s, thus Q = I x t.</div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Review the current probe data for the first 5-min electroplating trial.<strong> Note: </strong>If the current dropped to 0 or close to 0 at the end of the trial, then the electrons stopped flowing from the copper electrode to the key. Only use the values recorded before the drop in current occurred. If the current drop to 0 early in the plating process, repeat the trial.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">The current varies over time, so calculate the average current, I.
		<h4><strong>Table 2: Moles of Electrons Transferred</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td style="text-align: center;"><strong>Trial</strong></td>
					<td style="text-align: center;"><strong>Time (s) </strong></td>
					<td style="text-align: center;"><strong>Current<sub>average</sub> (A) </strong></td>
					<td style="text-align: center;"><strong>Total charge (C) </strong></td>
					<td style="text-align: center;"><strong>Moles (e?) </strong></td>
				</tr>
				<tr>
					<td style="text-align: center;">5 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">1<sup>st</sup> 30 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">2<sup>nd</sup> 30 min</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td style="text-align: center;">Total</td>
					<td></td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www-jove-com.bdigitaluss.remotexs.co/CDNSource/lm/labs/53/Table_2._Moles_of_Electrons_Transferred.xlsx" target="_blank">Click Here to download Table 2</a></div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Use the average current over the total time to determine the total charge transferred during electroplating, Q. About 20 coulombs were transferred during the 5-min trial, and between 110 and 120 coulombs were transferred during each 30-min trial. The total charge transferred over the entire 65-min electroplating process was about 250 coulombs.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Use the total charge transferred to calculate the moles of electrons plated during each trial. The moles of electrons plated equals the total charge transferred divided by the Faraday constant. The Faraday constant represents the magnitude of electric charge per mole of electrons and is determined by multiplying the charge of an electron by Avogadro&#39;s constant.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Determine the moles of electrons that were transferred for the 5-min and 30-min trials.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Calculate the moles of copper that were plated on the key after each trial. Similarly, determine the moles of copper lost from the copper sheet electrode.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Compare the moles of copper that were lost from the electrode to the amount that was plated to the brass key. The numbers should be close.</div>
		</li>
		<li data-sub-note-item="2-9">
		<div class="lab-step">Check to see if these values match what is expected based on the number of moles of electrons that were transferred. The reduction of 1 mole of copper(2+) ions requires 2 moles of electrons to produce 1 mole of solid copper.</div>
		</li>
	</ul>
	</li>
</ol>

Electrolytic Cells: Construction and Electroplating - Procedure

电解槽

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Electrolytic CellsExpand
	In this experiment, you will be assembling an electrolytic cell to ...

Proper Lab Notebook Keeping

<p>Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Nitration of Methyl Benzoate<button class="expand">Expand</button>
	<p>From this lab onward, you&#39;ll keep a record of every experiment in your lab notebook. This starts with preparing your lab notebook before you come to the lab. This preparation, which is often called a pre-lab, typically includes balanced chemical equations for the reactions, important properties of the reagents and products, and a step-by-step procedure for the lab in your own words. In this lab, you will perform the nitration of methyl benzoate, an aromatic ester that will undergo an electrophilic aromatic substitution to make methyl 3-nitrobenzoate.</p>
	<p>First, you&#39;ll mix aqueous sulfuric acid and nitric acid to make positive nitronium ions. In a separate container, you&#39;ll mix sulfuric acid with methyl benzoate to protonate the ester group. The way the charge is distributed makes the ring most reactive towards positive ions at the carbons one step away from the ester. This is known as the meta position in di-substituted benzene rings. When you combine the solutions, nitronium adds to methyl benzoate at one of those carbons. Then, the benzene ring and the ester group lose their extra protons to make methyl 3-nitrobenzoate.</p>
	<p>After the reaction, you&#39;ll dilute the mixture with water from melted ice and collect the insoluble product by vacuum filtration. At the end, you&#39;ll estimate the yield of your reaction based on the starting volume of methyl benzoate and the mass of the product.</p>
	<p>During the experiment, make sure to write down what you did and your observations as they happen. An accurate record is essential for reproducing your results and identifying sources of experimental error. Always catch up on your lab notebook before starting the next step.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-5">
		<div class="lab-step">Before you start the experiment, put on a lab coat, safety glasses, and nitrile gloves. Make sure to review the safety information in your pre-lab.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Fill a 100-mL beaker about halfway with crushed ice. <strong>Note:</strong> The reactions in this lab are exothermic, so use ice baths to keep the solutions cool.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Prepare the mixture of nitric acid and sulfuric acid. In your fume hood, clamp a 20-mL test tube upright in the ice bath. Label two 10-mL graduated cylinders &#8216;nitric acid&#8217; and &#8216;sulfuric acid&#8217;.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Measure 2 mL of concentrated sulfuric acid. If you add too much, use a pipette to transfer the excess to a small beaker labeled &#8216;sulfuric acid waste&#8217;.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Record the volume of sulfuric acid in your lab notebook as the volume used in the mixture of acids (Step 1). Pour the sulfuric acid into the test tube.
		<h4><strong>Table 1: Nitration of methyl benzoate</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td><strong>Step 1: Make positive nitronium ions</strong></td>
					<td style="text-align: center;">&#160; &#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
				</tr>
				<tr>
					<td>Volume of sulfuric acid (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Volume of nitiric acid (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Time of stirring (min)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td><strong>Step 2: Protonate ester on methyl benzoate</strong></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Volume of sulfuric acid (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Volume of methyl benzoate (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td><strong>Step 3: Combine solutions to form 3-methyl benzoate </strong></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Time of addition (min)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Reaction time on ice (min)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Reaction time at RT (min)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Yield of methyl 3-nitrobenzoate (g)</td>
					<td style="text-align: center;"></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www-jove-com.bdigitaluss.remotexs.co/CDNSource/lm/labs/55/Table_1._Nitration_of_methyl_benzoate.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Use the other graduated cylinder to measure 2 mL of concentrated nitric acid and pipette any extra nitric acid into a separate waste beaker. Record the volume of nitric acid in the graduated cylinder before pouring it into the test tube.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">Stir the solution for 2 min with a glass rod. Don&#39;t remove the solution from the ice bath. When you&#39;re done, record for how long you stirred the solution.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">Fill a 400-mL beaker about 3/4 full with ice and place it by an available lab stand in your fume hood. Clamp a clean 25-mL Erlenmeyer flask in this ice bath.</div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Prepare the mixture of sulfuric acid and methyl benzoate (Step 2). Measure another 2 mL of sulfuric acid with the corresponding graduated cylinder. Record the volume and carefully pour it into the Erlenmeyer flask.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Bring a clean 10-mL graduated cylinder, a pipette, and a small beaker to the solvent hood.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Carefully measure 1.1 mL of methyl benzoate and pipette any excess into the beaker for disposal in the organic waste. Remember to record the volume of methyl benzoate before pouring it into the flask of sulfuric acid.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Place a thermometer in the flask and wait for the solution to cool to between 10 &#176;C and 15 &#176;C.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Once the methyl benzoate solution is below 15 &#176;C, get a clean Pasteur pipette. Note the time in your lab notebook as the start of the solution addition and transfer the glass rod from the test tube to the Erlenmeyer flask (Step 3).</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">At a rate of 2 - 3 drops per min, add the mixed acids to the methyl benzoate solution and stir the mixture with the glass rod. Monitor the temperature of the solution throughout the addition process.<strong> Note: </strong>If the solution reaches 15 &#176;C, wait until the temperature has dropped below 15 &#176;C before adding more of the acid mixture. The addition process will take about 10 to 15 min.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Once you&#39;ve finished, note the time in your lab notebook and leave the flask in the ice bath for another 10 min while the mixture reacts.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Obtain about 20 mL of deionized water in a graduated cylinder. Fill a 600-mL beaker with ice and water and place the graduated cylinder in it to chill.</div>
		</li>
		<li data-sub-note-item="1-21">
		<div class="lab-step">Once the solution has reacted for 10 min on ice, remove the flask from the ice bath, record the time in your lab notebook, and let the solution continue reacting at room temperature for another 10 to 15 min.</div>
		</li>
		<li data-sub-note-item="1-22">
		<div class="lab-step">While you wait, fill a 100-mL beaker with about 25 mL of fresh ice. When the solution has reacted at room temperature for at least 10 min, record the time as the end of the reaction and pour the mixture into the 100-mL beaker containing ice. <strong>Note:</strong> Using ice lets you dilute the solution without heating it up too much because the heat from the reaction of sulfuric acid and water is expended on melting the ice.</div>
		</li>
		<li data-sub-note-item="1-23">
		<div class="lab-step">Wait for the ice to melt, which usually takes about 20 min. Remember to write down your observations, such as how long it took for the solid product to appear and what the precipitate looks like.</div>
		</li>
		<li data-sub-note-item="1-24">
		<div class="lab-step">Once the ice has melted completely, set up for vacuum filtration using a 250-mL filter flask. Place a filter paper in the funnel and use a clean pipette to wet the filter paper with cold water from the graduated cylinder.</div>
		</li>
		<li data-sub-note-item="1-25">
		<div class="lab-step">Open the flask to vacuum and pour your product mixture into the funnel. Rinse the remaining solid into the funnel with cold water. Then, pour the rest of the cold water into the funnel to wash the solid.</div>
		</li>
		<li data-sub-note-item="1-26">
		<div class="lab-step">Once no more liquid is dripping from the funnel into the flask, close the vacuum and break the vacuum seal. Carefully place the funnel in a beaker so that your product can dry overnight.</div>
		</li>
		<li data-sub-note-item="1-27">
		<div class="lab-step">Dispose of the filtrate in the aqueous acidic waste container. Pour the ice baths into the sink and wash your glassware using your usual methods. Dispose of used Pasteur pipettes in the glass waste container, neutralize and clean up any spilled acid, and throw out paper waste in the lab trash.</div>
		</li>
		<li data-sub-note-item="1-28">
		<div class="lab-step">Calculate the theoretical yield of methyl 3-nitrobenzoate in g.
		<h4><strong>Table 2: Product yield of methyl 3-methyl benzoate</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td>Volume of methyl benzoate (mL)</td>
					<td style="text-align: center;">&#160; &#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</td>
				</tr>
				<tr>
					<td>Density of methyl benzoate (g/cm3)</td>
					<td style="text-align: center;">1.08</td>
				</tr>
				<tr>
					<td>Molecular weight of methyl benzoate (g/mol)</td>
					<td style="text-align: center;">136.15</td>
				</tr>
				<tr>
					<td>Amount of methyl benzoate (mol)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Molecular weight of methyl 3-nitrobenzoate (g/mol)</td>
					<td style="text-align: center;">181.15</td>
				</tr>
				<tr>
					<td>Theoretical yield of methyl 3-nitrobenzoate (g)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Actual yield of methyl 3-nitrobenzoate (g)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Actual yield of methyl 3-nitrobenzoate (mol)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Percent yield</td>
					<td style="text-align: center;"></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www-jove-com.bdigitaluss.remotexs.co/CDNSource/lm/labs/55/Table_2._Product_yield_of_methyl_3-methylbenzoate.xlsx" target="_blank">Click Here to download Table 2</a></div>
		</li>
		<li data-sub-note-item="1-29">
		<div class="lab-step">The next day, check on your product. If it seems dry, bring your funnel to a balance to weigh your product.<strong>Note:</strong> If it seems wet, leave it to dry some more.</div>
		</li>
		<li data-sub-note-item="1-30">
		<div class="lab-step">Tare a weighing boat and use a small spatula to carefully transfer the product from the filter paper to the weighing boat.</div>
		</li>
		<li data-sub-note-item="1-31">
		<div class="lab-step">Compare the mass of your product to the theoretical yield. If the mass reading is stable and less than the theoretical yield, you can assume that the product is dry. Record this mass in your lab notebook.</div>
		</li>
		<li data-sub-note-item="1-32">
		<div class="lab-step">Throw out the solid product and the filter paper in the lab trash and wash the B&#252;chner funnel.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Results<button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="2-1">
		<div class="lab-step">Calculate the yield of your reaction. From the theoretical maximum yield, convert the mass of your product to moles.</div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Divide that amount by the maximum yield and multiply it by 100. The total nitrated product yield, which includes minor products, is usually about 85%.</div>
		</li>
	</ul>
	</li>
</ol>

正确保存实验室笔记本

Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA

	Nitration of Methyl BenzoateExpand
	From this lab onward, ...

Scientific Measurement and Lab Skills

Two-Dimensional Graphs, Curve Fitting, and Standard Deviation - Procedure

科学测量和实验室技能

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Measuring Diameter and CircumferenceExpand
	Error can be introduced in any experiment, even ...

Acid and Base Concentrations

<p>Source: Smaa Koraym at Johns Hopkins University, MD, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Preparation of ~0.1 M NaOH<button class="expand">Expand</button>
	<p>In the first part of the lab, you will use a 50% w/w solution of NaOH to prepare 500 mL of ~0.1 M. The 50% w/w NaOH is indicative of its weight ratio. For example, if the instructor prepared 150 mL of the 50% w/w NaOH solution, then 150 g of NaOH was dissolved in 150 g of water, and the total weight of the solution is 300 g.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-2">
		<div class="lab-step">To begin, put on the appropriate personal protective equipment, including gloves, chemical splash goggles, and a lab coat.</div>
		</li>
		<li data-sub-note-item="1-3">
		<div class="lab-step">Calculate the molarity of 50% w/w NaOH, which is M<sub>1</sub> in the dilution formula.<strong> Note: </strong>The density of 50% w/w NaOH is 1.53 g/mL, and the molar mass of NaOH is 39.998 g/mole.
		<h4>Table 1. Preparation of 0.1 M NaOH from 50% w/w NaOH</h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td>Density of 50% w/w stock solution</td>
					<td style="text-align: center;">1.53 g/mL</td>
				</tr>
				<tr>
					<td>Molar mass<sub>NaOH</sub></td>
					<td style="text-align: center;">39.998 g/mol</td>
				</tr>
				<tr>
					<td>Mass of NaOH in 50% w/w stock solution (mg)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Total mass of 50% w/w stock solution</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Volume of 50% w/w stock solution (mL)</td>
					<td></td>
				</tr>
				<tr>
					<td>Moles of NaOH in 50% w/w solution (mol)</td>
					<td></td>
				</tr>
				<tr>
					<td>Molarity of 50% w/w stock solution (M<sub>1</sub>)</td>
					<td></td>
				</tr>
				<tr>
					<td>Volume of 50% w/w solution needed (V<sub>1</sub>)</td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www-jove-com.bdigitaluss.remotexs.co/CDNSource/lm/labs/44/Table_1._Preparation_of_0.1_M_NaOH.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Use the dilution formula to determine the volume of 50% w/w NaOH needed to prepare 500 mL of ~0.1 M NaOH.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Label the 500 mL polyethylene bottle as &#8216;~0.1 M NaOH&#8217;.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Adjust the volume on a 1-mL pipette to the value calculated and use it to transfer the 50% w/w NaOH to the polyethylene bottle.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Use a 100-mL graduated cylinder to measure the amount of water and pour it into the bottle containing the NaOH. Cap the bottle and invert it several times to mix the solution. <strong>Note:</strong> You will need 500 mL minus the calculated volume of NaOH.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Standardization of 0.1 M NaOH<button class="expand">Expand</button>
	<p>After you have prepared 0.1 M NaOH, determine its exact concentration, or standardize it, using the acid-base titration method. In this technique, a base like NaOH is slowly added to an acid like potassium hydrogen phthalate (KHP). The chemical reaction that takes place in the flask is a neutralization reaction. In this neutralization reaction, one mole of base neutralizes one mole of acid, resulting in salt and water. This reaction is performed in the presence of the indicator phenolphthalein, which is colorless at the start of the reaction when the pH is acidic. The indicator turns pink as soon as enough NaOH is added to the flask to make the pH basic.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-2">
		<div class="lab-step">Label the three Erlenmeyer flasks as &#8216;A&#8217;, &#8216;B&#8217;, and &#8216;C&#8217;.</div>
		</li>
		<li data-sub-note-item="2-3">
		<div class="lab-step">Weigh 0.5 &#8211; 0.7 g of KHP for each of the flasks and record the mass for each. <strong>Note: </strong>Try to measure the same mass of KHP for all three flasks.
		<h4><strong>Table 2. Standardization of NaOH</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td><strong>Molar mass<sub>KHP</sub> = 204.23 g/mol </strong></td>
					<td style="text-align: center;"><strong>Flask A</strong></td>
					<td style="text-align: center;"><strong>Flask B</strong></td>
					<td style="text-align: center;"><strong>Flask C</strong></td>
				</tr>
				<tr>
					<td>Mass of KHP (g)</td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Volume<sub>initial NaOH</sub>(mL)</td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Volume<sub>final NaOH</sub> (mL)</td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Volume<sub>NaOH</sub> (mL)</td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Moles of KHP</td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Moles of NaOH</td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Molarity of NaOH</td>
					<td></td>
					<td></td>
					<td></td>
				</tr>
				<tr>
					<td>Average molarity</td>
					<td></td>
				</tr>
				<tr>
					<td>Standard deviation</td>
					<td></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www-jove-com.bdigitaluss.remotexs.co/CDNSource/lm/labs/44/Table_2._Standardization_of_NaOH.xlsx" target="_blank">Click Here to download Table 2</a></div>
		</li>
		<li data-sub-note-item="2-4">
		<div class="lab-step">Add 50 mL of deionized water to each flask, and use a glass stirring rod to stir the solutions until they appear homogeneous.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Add 2-3 drops of phenolphthalein to each of the three flasks.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Set up the titration apparatus. Attach the burette clamp to the ring stand, and securely clamp the 50-mL glass burette to it. Make sure the valve of the burette is closed.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Label a 400-mL beaker as &#8216;waste&#8217; and place it under the burette. Rinse the burette by pouring about 5 mL of 0.1 M NaOH into the burette. Open the burette valve to allow the NaOH to flow into the beaker.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">Close the valve and fill the burette with slightly more than 50 mL of NaOH. Release any air bubbles present in the tip of the burette by opening and closing the burette valve. Record the starting volume of NaOH.</div>
		</li>
		<li data-sub-note-item="2-9">
		<div class="lab-step">Place flask A below the tip of the burette, and titrate the solution using 1 mL volumes of NaOH. Swirl the solution after each addition. Continue adding 1 mL volumes to the flask until the pink color persists. This is considered the endpoint. Record the volume of 0.1 M NaOH added to achieve the endpoint.</div>
		</li>
		<li data-sub-note-item="2-10">
		<div class="lab-step">Repeat the titration for flasks B and C. This data will be used to calculate the actual concentration of NaOH.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="3" data-parent-collapse="">Titration of phosphoric acid<button class="expand">Expand</button>
	<p>In this experiment, we will determine two of the three pKa values for the triprotic acid, phosphoric acid, using acid-base titration. In this neutralization reaction, phosphoric acid reacts with NaOH to form water and the salt, sodium phosphate.</p>
	<ul class="lab-items">
		<li data-sub-note-item="3-2">
		<div class="lab-step">Attach the drop counter to the ring stand, below the burette clamp. Secure the plastic burette so that its tip is just above the drop counter.</div>
		</li>
		<li data-sub-note-item="3-3">
		<div class="lab-step">Connect the drop counter to the data acquisition system, and make sure the two valves of the plastic burette are both in the closed position.</div>
		</li>
		<li data-sub-note-item="3-4">
		<div class="lab-step">Place the waste container below the burette and pour a few mL of 0.1 M NaOH into the burette. Open both valves to drain the NaOH into the waste beaker. Then close the valves.</div>
		</li>
		<li data-sub-note-item="3-5">
		<div class="lab-step">Fill the plastic burette with 25 mL of 0.1 M NaOH. Drain about 5 mL into the waste beaker&#8212;enough so that NaOH fills the burette tip. Make sure there are no air bubbles, then close the valves.</div>
		</li>
		<li data-sub-note-item="3-6">
		<div class="lab-step">Calibrate the drop counter. Replace the waste beaker beneath the burette with a 10-mL graduated cylinder. Then, open the bottom valve on the burette, while keeping the top valve closed. Turn on the data acquisition system and set it to &#8216;drop counting mode&#8217;.</div>
		</li>
		<li data-sub-note-item="3-7">
		<div class="lab-step">Slowly open the top valve to very slowly release drops, ideally at one drop every 2 s. Allow the drops to empty from the burette until there is 9-10 mL of 0.1 M NaOH in the graduated cylinder.</div>
		</li>
		<li data-sub-note-item="3-8">
		<div class="lab-step">Close the bottom valve and leave the top valve as is. Read the volume of NaOH in the graduated cylinder to the first decimal place and enter this value in the data acquisition system. Record the value for &#8216;drops/mL&#8217;. Then, discard the NaOH in the graduated cylinder into the aqueous waste beaker.</div>
		</li>
		<li data-sub-note-item="3-9">
		<div class="lab-step">Calibrate the pH sensor before starting the titration. Connect the pH sensor to the data acquisition system, then select &#39;Calibrate&#39;. Rinse the bulb of the pH sensor with deionized water before inserting it into the pH 7 buffer. Leave the sensor submerged until the voltage stabilizes, then accept the measurement.</div>
		</li>
		<li data-sub-note-item="3-10">
		<div class="lab-step">Rinse the bulb with deionized water and insert it into the pH 10 buffer. Allow the voltage to stabilize, then accept the measurement.</div>
		</li>
		<li data-sub-note-item="3-11">
		<div class="lab-step">Rinse the bulb of the pH sensor again and slide it through the designated slot in the drop counter.</div>
		</li>
		<li data-sub-note-item="3-12">
		<div class="lab-step">Measure 40 mL of deionized water into a clean 100-mL beaker, then, transfer 1 mL of phosphoric acid into the beaker of water.</div>
		</li>
		<li data-sub-note-item="3-13">
		<div class="lab-step">Place the beaker on the stir plate under the drop counter. Carefully slide the pH sensor into the beaker.</div>
		</li>
		<li data-sub-note-item="3-14">
		<div class="lab-step">Add a stir bar to the beaker, and turn the stir setting onto high. Start collecting data on the acquisition device. Then, open the bottom valve on the burette. <strong>Note: </strong>The drop rate should be about 1 drop every 2 s. After the first drop is released, check to see data are being recorded.</div>
		</li>
		<li data-sub-note-item="3-15">
		<div class="lab-step">Continue the titration until the pH meter reads pH 12. Then, stop acquiring data and close the valve on the burette. Save your data on a flash drive.</div>
		</li>
		<li data-sub-note-item="3-16">
		<div class="lab-step">To clean up your workspace, check the pH of all waste solutions using pH paper. Neutralize all acidic aqueous waste with baking soda and all basic waste with citric acid. Add enough of either baking soda or citric acid to the solution until it stops bubbling.</div>
		</li>
		<li data-sub-note-item="3-17">
		<div class="lab-step">Flush all neutralized solutions down the sink with copious amounts of water.</div>
		</li>
		<li data-sub-note-item="3-18">
		<div class="lab-step">Wash all glassware.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="4" data-parent-collapse="">Results<button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="4-1">
		<div class="lab-step">In the first part of this lab, you standardized a solution of NaOH using KHP to determine its actual concentration. Now, let&#39;s see how close the standardized concentration is to the 0.1 M concentration that was prepared. Determine the number of moles of KHP that was added to each flask, and by extension, the moles of NaOH. Once the solution is neutralized, the molar quantities of KHP and NaOH are equal.</div>
		</li>
		<li data-sub-note-item="4-2">
		<div class="lab-step">Calculate the molarity of NaOH based on the total volume of NaOH that was added to each flask. The actual concentration is lower than the expected 0.1 molarity. This is because NaOH is hygroscopic, so it is difficult to weigh it accurately.</div>
		</li>
		<li data-sub-note-item="4-3">
		<div class="lab-step">Plot the results for the phosphoric acid titration (pH vs. Volume of NaOH). Phosphoric acid is a weak triprotic acid, meaning that it has the potential to provide three protons per molecule when it dissociates in aqueous solutions. Phosphoric acid has three pKa values, one for when each proton is dissociated.</div>
		</li>
		<li data-sub-note-item="4-4">
		<div class="lab-step">Look at the data. There are two sigmoidal curves, indicating two equivalence points. Each equivalence point corresponds to a dissociation constant, Ka, of phosphoric acid. <strong>Note: </strong>You stopped the experiment once the pH reached 12, so you only measured two of the three Ka values.</div>
		</li>
		<li data-sub-note-item="4-5">
		<div class="lab-step">Plot the first derivative of the titration curve. The equivalence points are represented by the curve maximums.
		<h4><strong>Table 3. Titration of phosphoric acid</strong></h4>
		<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
			<tbody>
				<tr>
					<td>Volume<sub>1<sup>st</sup> equivalence point</sub> (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Volume<sub>1<sup>st</sup> half-equivalence point</sub> (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Volume<sub>2<sup>nd</sup> equivalence point</sub> (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Volume<sub>2<sup>nd</sup> half-equivalence point</sub> (mL)</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>1<sup>st</sup> pKa<sub>measured</sub></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>1<sup>st</sup> pKa<sub>theoretical</sub></td>
					<td style="text-align: center;">2.16</td>
				</tr>
				<tr>
					<td>2<sup>nd</sup> pKa<sub>measured</sub></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>2<sup>nd</sup> pKa<sub>theoretical</sub></td>
					<td style="text-align: center;">7.21</td>
				</tr>
				<tr>
					<td>Moles of NaOH</td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Moles of H<sub>3</sub>PO<sub>4</sub></td>
					<td style="text-align: center;"></td>
				</tr>
				<tr>
					<td>Molarity of H<sub>3</sub>PO<sub>4</sub></td>
					<td style="text-align: center;"></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www-jove-com.bdigitaluss.remotexs.co/CDNSource/lm/labs/44/Table_3._Titration_of_Phosphoric_Acid.xlsx" target="_blank">Click Here to download Table 3</a></div>
		</li>
		<li data-sub-note-item="4-6">
		<div class="lab-step">Find the first half-equivalence point by taking the volume of NaOH corresponding to the first equivalence point and dividing it by 2. At the half-equivalence point, the concentrations of undissociated acid and its conjugate base are the same, and the pH is equal to the pKa.</div>
		</li>
		<li data-sub-note-item="4-7">
		<div class="lab-step">Look up the pH at this volume from your table of data to get a more precise value. This corresponds to the first pKa, which is reported in the literature as 2.16.</div>
		</li>
		<li data-sub-note-item="4-8">
		<div class="lab-step">Repeat this to find the second pKa. The second half-equivalence point is located midway between the first and second equivalence points, which should give a pKa of about 7.2.</div>
		</li>
	</ul>
	</li>
</ol>

Acid-Base Titration: Calculating pH, Strength, and Concentration - Procedure

酸和碱浓度

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Preparation of ~0.1 M NaOHExpand
	In the first part of the lab, you will use a 50% w/w solution ...

Enthalpy of Reaction

Enthalpy of Reaction and Measurement of Heat by Calorimeter - procedure

反应焓

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Collecting Data for Calculating the Heat Capacity of a CalorimeterExpand
	This experiment will ...

Physiology of the Circulatory System

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Measuring Circulatory System Function in Humans
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">Before starting the experiment go to the front of the room and collect an alcohol swab, a sphygmomanometer, and a stethoscope.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">Clean the earpieces with the alcohol swab and then insert them into your ears.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">To check if the stethoscope is in the on position, gently tap the flat metal disc called the diaphragm.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">If you hear a sound it&#39;s on. If not, turn the metal disc and tap again and keep turning and tapping the disc until you hear a sound. NOTE: For this experiment you will work in pairs. One person will measure their partner&#39;s blood pressure, while the person being measured will count their heartbeats over the course of one minute.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Fill out table one with the name of the person being monitored. HYPOTHESES: The experimental hypothesis is that systolic blood pressure will be higher when the person is sitting when compared to lying down because more pressure is required for blood to be moved around the body. The null hypothesis is that there will be no difference in systolic blood pressure whether a person is sitting or lying down.<a href="https://www-jove-com.bdigitaluss.remotexs.co/CDNSource/lm/labs/9/Table_1_Physiology_of_Circulatory_System.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 1</a>
</div></li><li data-sub-note-item="1-6"><div class="lab-step">The person being monitored should begin by lying down. Next, they will need to locate their pulse by placing two fingers next to their windpipe. If a throbbing sensation is felt, this is the pulse.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Now, ready a time keeping device to count out 1 minute as the person taking their pulse will be having their blood pressure taken at the same time.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">At this point, the person measuring blood pressure should place the cuff of the sphygmomanometer around the other arm of the subject and the stethoscope earpieces into their own ears.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Start the timer.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">The person being monitored should begin counting the number of heartbeats felt over one full minute. While the subject is taking their pulse, the person taking blood pressure should place the diaphragm of the stethoscope under the cuff on the inside of their partner&#39;s elbow.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">Then, pump the cuff to 200 mm of mercury.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Gently and slowly twist the metal knob on the sphygmomanometer to release air from the cuff.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">As pressure is released the first Korotkoff sound should be heard. The corresponding value on the sphygmomanometer is the systolic blood pressure. Consistent sounds should be heard until they die out with the last sound signifying the diastolic blood pressure.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Record the systolic pressure, the diastolic pressure, and the heart rate in Table 1.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Now, repeat the blood pressure and pulse measurements with each partner keeping the same role but this time the subject should be sitting upright.
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Record these data in the appropriate places in Table 1.
</div></li><li data-sub-note-item="1-17"><div class="lab-step">Finally, the partners should switch spots. So now, the person measuring blood pressure should be taking their pulse and acting as the subject.  NOTE: Be sure to wipe the earpieces of the stethoscope between users and don&#39;t forget to record your measurements in Table 1.
</div></li><li data-sub-note-item="1-18"><div class="lab-step">After finishing the experiment, discard all alcohol swabs into the trash. Then, bring the sphygmomanometer and stethoscope back to the front of the room.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Measuring Respiratory Rate in Fish
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">To prepare for this second experiment, collect two clear containers.
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Begin by filling half of one container with aquarium water.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">Then, use a fish net to gently catch a goldfish and place it into the cup. Pinch the net around the fish or else it may jump out of the net.
</div></li><li data-sub-note-item="2-4"><div class="lab-step">Familiarize yourself with the operculum of the fish. The operculum covers the gills and it is located behind and below the eye. When the fish respires the operculum moves in and out and this is one gill beat. HYPOTHESES: In this experiment you will measure the gill beats of the fish in different water temperatures. The hypothesis is that there will be a significant correlation between the temperature and respiration rate in goldfish. The null hypothesis is that there will be no correlation between temperature and respiration rate.
</div></li><li data-sub-note-item="2-5"><div class="lab-step">Take the other empty container with a screw cap, the cup with your fish, and the net to the water tanks.
</div></li><li data-sub-note-item="2-6"><div class="lab-step">Then, fill the empty container with the water from the lowest temperature water bath. This will act as your first respiration rate chamber.
</div></li><li data-sub-note-item="2-7"><div class="lab-step">Next, hold the fish net over a wastewater container and dump out the water from the cup holding the fish so that the fish falls into the net. Pinch the net around the fish without touching the fish itself.
</div></li><li data-sub-note-item="2-8"><div class="lab-step">Bring the net over the top of the container with the bath water and let go of the net to release the fish into the vial.
</div></li><li data-sub-note-item="2-9"><div class="lab-step">Once the fish is in the container, submerge it back into the water bath and then screw the cap on to prevent outside oxygen from entering the vial.
</div></li><li data-sub-note-item="2-10"><div class="lab-step">Next, remove the container from the controlled temperature water bath and place it on your workbench surface to avoid warming the water with body heat.
</div></li><li data-sub-note-item="2-11"><div class="lab-step">One partner should immediately begin counting the gill beats as soon as the second partner starts the stopwatch.
</div></li><li data-sub-note-item="2-12"><div class="lab-step">Continue counting the beats for 20 seconds. Record the number of beats in column A of Table 2. <a href="https://www-jove-com.bdigitaluss.remotexs.co/CDNSource/lm/labs/9/Table_2_Physiology_of_Circulatory_System.xlsx" style="display:block;margin:20px;" target="__blank">Click Here to download Table 2</a>
</div></li><li data-sub-note-item="2-13"><div class="lab-step">Repeat the measurement one more time and record the number in column B.
</div></li><li data-sub-note-item="2-14"><div class="lab-step">Next, hold the fish net over a wastewater container and dump out the water from the fish vial so that the fish falls into the net.  IMPORTANT: Move from lowest to highest temperature, so the fish is not stressed between trials.
</div></li><li data-sub-note-item="2-15"><div class="lab-step">Repeat the experiment for the remaining four temperature conditions (steps 8 &#8211; 13).
</div></li><li data-sub-note-item="2-16"><div class="lab-step">Record all the values for different temperatures in Table 2.
</div></li><li data-sub-note-item="2-17"><div class="lab-step">Once you are done, slowly mix water from the last respiration chamber with the fish tank water and then return the fish to the home tank. NOTE: This should be done over the course of approximately 10 minutes.
</div></li></ul></li><li data-note-item="3" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="3-1"><div class="lab-step">It&#39;s time to analyze the data that you just collected. Look at the blood pressure and heart rate measurements for the different trials. If they were different, make a hypothesis to explain your observations. 
</div></li><li data-sub-note-item="3-2"><div class="lab-step">For the gill beat experiment, average the numbers in columns A and B and calculate the fish respiration rate as gill beats per minute.
</div></li><li data-sub-note-item="3-3"><div class="lab-step">Next, plot the graph of temperature versus gill beats per minute.
</div></li><li data-sub-note-item="3-4"><div class="lab-step">Record any correlations you see between the variables. If a correlation is observed, determine if it is positive or negative and provide an explanation for this result.  NOTE: Consider the fact that fishes are ectotherms and the impact of temperature on dissolved oxygen.
</div></li></ul></li></ol>

循环系统的生理学

Measuring Circulatory System Function in Humans
ExpandBefore starting the experiment go to the front of the room and collect an alcohol swab, a ...

生物学

科学探究

Transpiration

<ol class="note-items"><li data-note-item="1" data-parent-collapse="">Comparing Transpiration Rates of Leaves
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="1-1"><div class="lab-step">To begin the experiment to measure the transpiration rates of leaves from different plant species, you will first create a tool called a potometer, using a piece of plastic tubing and 5 mL calibrated pipette.
</div></li><li data-sub-note-item="1-2"><div class="lab-step">To assemble the device, simply attach the rubber tubing to the tip of the pipette.
</div></li><li data-sub-note-item="1-3"><div class="lab-step">Then, submerge the device into a bucket of water and move the pipette around under the water to fully fill the tube, taking care not to create bubbles.
</div></li><li data-sub-note-item="1-4"><div class="lab-step">Next, cap the open end of the tube with a pipette bulb to keep the water in.
</div></li><li data-sub-note-item="1-5"><div class="lab-step">Now, taking care not to spill water from the potometer, use a clamp and stand to hold the capped end of the pipette around 1 - 3 inches below the pipette bulb.
</div></li><li data-sub-note-item="1-6"><div class="lab-step">Then, use a second clamp attached lower on the same stand to secure the open end of the rubber tubing.
</div></li><li data-sub-note-item="1-7"><div class="lab-step">Next, use a transfer pipette or dropper to remove water from the open end of the tubing until the water level in the pipette portion of the potometer rests at the zero line. HYPOTHESES: In this experiment, the experimental hypothesis might be that leaves from plant species more adapted to hotter or arid environments will have lower transpiration rates than those from humid or wet regions. The null hypothesis would be that leaves of the different plant species will not differ in their transpiration rates.
</div></li><li data-sub-note-item="1-8"><div class="lab-step">To begin the experiment, carefully use scissors to cut the end of the petiole, or stalk, of the first leaf and then insert the leaf into the tubing.
</div></li><li data-sub-note-item="1-9"><div class="lab-step">Then, place a layer of lubricant around the area where the plant stem and rubber tubing meet to make a watertight seal.
</div></li><li data-sub-note-item="1-10"><div class="lab-step">Next, remove the pipette bulb and taking care not to disturb the setup, let the experiment run for the appropriate experimental period, typically 30 - 60 minutes.
</div></li><li data-sub-note-item="1-11"><div class="lab-step">At the end of the allocated time, record the level of the water in the pipette, noting how much the level dropped in milliliters.
</div></li><li data-sub-note-item="1-12"><div class="lab-step">Then, refill and reset the potometer water level to zero, and then repeat the procedure for each of the remaining test leaves until the transpiration rates of all four leaves have been measured.
</div></li><li data-sub-note-item="1-13"><div class="lab-step">Next, to determine the surface area of the leaf samples, lay each leaf on a blank piece of paper and carefully trace the outlines.
</div></li><li data-sub-note-item="1-14"><div class="lab-step">Then, cut the outlines out and record the mass of each tracing.
</div></li><li data-sub-note-item="1-15"><div class="lab-step">Finally, cut out and weigh one four by four centimeter square of the same type of paper used to make the leaf tracings. This will act as a reference with known area and weight.
</div></li><li data-sub-note-item="1-16"><div class="lab-step">Next, you will need to quantify the number of stomata per unit area on each leaf. To do this, first prepare a slide mount by painting at least one square centimeter of the underside of each leaf with clear nail polish. IMPORTANT: Ensure you paint the bottom of the leaf, since the majority of the stomata are located there. 
</div></li><li data-sub-note-item="1-17"><div class="lab-step">When the nail polish is completely dry, carefully press a small piece of cellophane tape directly onto each patch and then gently peel off the tape to remove the painted on polish. NOTE: Use a piece of tape that is smaller than the microscope slide. 
</div></li><li data-sub-note-item="1-18"><div class="lab-step">Then, place each impression and tape onto a separate, clean microscope slide. HYPOTHESES: In this exercise, the alternative hypothesis could be that the leaves of the plants adapted to drier environments will have fewer stomata per unit area than the leaves of plants adapted to wetter environments. The null hypothesis might be that all plants species will have an equal number of stomata per unit area.
</div></li><li data-sub-note-item="1-19"><div class="lab-step">To observe each impression under the microscope, first use a low magnification to find areas of the leaf impression that contain stomata. These will appear as darker dots or impressions.
</div></li><li data-sub-note-item="1-20"><div class="lab-step">Then, switch to a higher magnification, keeping the sample viewing window centered on the stomata-containing area.
</div></li><li data-sub-note-item="1-21"><div class="lab-step">Draw and label your observations, making sure to label each sketch with the plant species.
</div></li><li data-sub-note-item="1-22"><div class="lab-step">Then, count and record the number of stomata in the field of view. You should perform this count a total of four times in four different areas of the leaf impression, and then determine the average number of stomata per counted area on the leaf.
</div></li><li data-sub-note-item="1-23"><div class="lab-step">To calculate the number of stomata per mm<sup>2</sup>, place a transparent plastic ruler on the microscope stage under the objective and measure the diameter of the field of view.
</div></li><li data-sub-note-item="1-24"><div class="lab-step">You can then use this number, the diameter or D, to calculate the area of the field of view in mm<sup>2</sup>.
</div></li></ul></li><li data-note-item="2" data-parent-collapse="">Results
<button class="expand">Expand</button><ul class="lab-items"><li data-sub-note-item="2-1"><div class="lab-step">First, calculate the surface area of the 4x4 cm paper square to obtain the number of square centimeters.
</div></li><li data-sub-note-item="2-2"><div class="lab-step">Then, divide the weight of the paper square by the number of centimeters squared it covers to obtain the weight of 1 cm<sup>2</sup> of paper.
</div></li><li data-sub-note-item="2-3"><div class="lab-step">Finally, to calculate the surface area of each leaf, divide the weight of the leaf tracing by the weight of 1 cm<sup>2</sup> of paper. This will give you leaf area in centimeters squared.
</div></li><li data-sub-note-item="2-4"><div class="lab-step">You should now convert this number to meters squared, the standard unit used for calculating transpiration rate.
</div></li><li data-sub-note-item="2-5"><div class="lab-step">To calculate the transpiration rate for each leaf, divide the total water loss you measured in the potometer in mL by the time the experiment was run for in minutes.
</div></li><li data-sub-note-item="2-6"><div class="lab-step">Then, divide this by the surface area of the leaf in m<sup>2</sup>.
</div></li><li data-sub-note-item="2-7"><div class="lab-step">Make a bar graph with the four different leaf species on the X axis, and their corresponding transpiration rates on the Y axis. Do these rates appear different?
</div></li><li data-sub-note-item="2-8"><div class="lab-step">Next, add a second Y axis to your chart and plot the average number of stomata per millimeter squared for each leaf that was observed under the microscope. Do you see a correlation between transpiration rate and number of stomata? If so, does this seem to have any relationship to the native environment the tree would typically inhabit?
</div></li></ul></li></ol>

Assessing Transpiration Rates using Potometer - Procedure

蒸腾作用

Comparing Transpiration Rates of Leaves
ExpandTo begin the experiment to measure the transpiration rates of leaves from different plant species, you will ...