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<title>Cooling bath</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Cooling bath</span></span>

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<p>A <b>cooling bath</b> or <b>ice bath</b>, in laboratory chemistry practice, is a liquid mixture which is used to maintain low temperatures, typically between 13 °C and −196 °C. These low temperatures are used to collect liquids after <a href="Distillation" title="Distillation">distillation</a>, to remove solvents using a <a href="Rotary_evaporator" title="Rotary evaporator">rotary evaporator</a>, or to perform a <a href="Chemical_reaction" title="Chemical reaction">chemical reaction</a> below room temperature (see <a href="Kinetic_control" class="mw-redirect" title="Kinetic control">Kinetic control</a>).

</p><p>Cooling baths are generally one of two types: (a) a cold fluid (particularly <a href="Liquid_nitrogen" title="Liquid nitrogen">liquid nitrogen</a>, <a href="Water" title="Water">water</a>, or even <a href="Air" class="mw-redirect" title="Air">air</a>) — but most commonly the term refers to (b) a mixture of 3 components: (1) a cooling agent (such as <a href="Dry_ice" title="Dry ice">dry ice</a> or <a href="Ice" title="Ice">ice</a>); (2) a liquid "carrier" (such as liquid water, <a href="Ethylene_glycol" title="Ethylene glycol">ethylene glycol</a>, <a href="Acetone" title="Acetone">acetone</a>, etc.), which transfers heat between the bath and the vessel; (3) an additive to depress the melting point of the solid/liquid system.

</p><p>A familiar example of this is the use of an ice/rock-salt mixture to freeze ice cream. Adding salt lowers the freezing temperature of water, lowering the minimum temperature attainable with only ice.

</p>

<caption>Mixed solvent cooling baths (% by volume)<sup id="cite_ref-autogenerated629_1-0" class="reference"><a href="#cite_note-autogenerated629-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

</caption>

<th>% Glycol in EtOH

</th>

<th>Temp (°C)

</th>

<th>% H<sub>2</sub>O in MeOH

</th>

<th>Temp (°C)

</th></tr>

<tr>

<td>0%

</td>

<td>−78

</td>

<td>0%

</td>

<td>−97.6

</td></tr>

<tr>

<td>10%

</td>

<td>−76

</td>

<td>14%

</td>

<td>−128

</td></tr>

<tr>

<td>20%

</td>

<td>−72

</td>

<td>20%

</td>

<td>N/A

</td></tr>

<tr>

<td>30%

</td>

<td>−66

</td>

<td>30%

</td>

<td>−72

</td></tr>

<tr>

<td>40%

</td>

<td>−60

</td>

<td>40%

</td>

<td>−64

</td></tr>

<tr>

<td>50%

</td>

<td>−52

</td>

<td>50%

</td>

<td>−47

</td></tr>

<tr>

<td>60%

</td>

<td>−41

</td>

<td>60%

</td>

<td>−36

</td></tr>

<tr>

<td>70%

</td>

<td>−32

</td>

<td>70%

</td>

<td>−20

</td></tr>

<tr>

<td>80%

</td>

<td>−28

</td>

<td>80%

</td>

<td>−12.5

</td></tr>

<tr>

<td>90%

</td>

<td>−21

</td>

<td>90%

</td>

<td>−5.5

</td></tr>

<tr>

<td>100%

</td>

<td>−17

</td>

<td>100%

</td>

<td>0

</td></tr></tbody></table>

<div class="mw-heading mw-heading2"><h2 id="Mixed-solvent_cooling_baths">Mixed-solvent cooling baths</h2></div>

<p>Mixing solvents creates cooling baths with variable freezing points. Temperatures between approximately −78 °C and −17 °C can be maintained by placing coolant into a mixture of <a href="Ethylene_glycol" title="Ethylene glycol">ethylene glycol</a> and <a href="Ethanol" title="Ethanol">ethanol</a>,<sup id="cite_ref-autogenerated629_1-1" class="reference"><a href="#cite_note-autogenerated629-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> while mixtures of <a href="Methanol" title="Methanol">methanol</a> and <a href="Water" title="Water">water</a> span the −128 °C to 0 °C temperature range.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Dry ice <a href="Sublimation_(phase_transition)" title="Sublimation (phase transition)">sublimes</a> at −78 °C, while <a href="Liquid_nitrogen" title="Liquid nitrogen">liquid nitrogen</a> is used for colder baths.

</p><p>As water or ethylene glycol freeze out of the mixture, the concentration of ethanol/methanol increases. This leads to a new, lower freezing point. With dry ice, these baths will never freeze solid, as pure methanol and ethanol both freeze below −78 °C (−98 °C and −114 °C respectively).

</p><p>Relative to traditional cooling baths, solvent mixtures are adaptable for a wide temperature range. In addition, the solvents necessary are cheaper and less toxic than those used in traditional baths.<sup id="cite_ref-autogenerated629_1-2" class="reference"><a href="#cite_note-autogenerated629-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

</p>

<div class="mw-heading mw-heading2"><h2 id="Traditional_cooling_baths">Traditional cooling baths</h2></div>

<caption>Traditional cooling bath mixtures<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

</caption>

<th>Cooling agent

</th>

<th>Organic solvent or salt

</th>

<th>Temp (°C)

</th></tr>

<tr>

<td>Dry ice

</td>

<td><i>p</i>-xylene

</td>

<td>+13

</td></tr>

<tr>

<td>Dry ice

</td>

<td>Dioxane

</td>

<td>+12

</td></tr>

<tr>

<td>Dry ice

</td>

<td>Cyclohexane

</td>

<td>+6

</td></tr>

<tr>

<td>Dry ice

</td>

<td>Benzene

</td>

<td>+5

</td></tr>

<tr>

<td>Dry ice

</td>

<td>Formamide

</td>

<td>+2

</td></tr>

<tr>

<td>Ice

</td>

<td>Salts (see: left)

</td>

<td>0 to −40

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td>Cycloheptane

</td>

<td>−12

</td></tr>

<tr>

<td>Dry ice

</td>

<td>Benzyl alcohol

</td>

<td>−15

</td></tr>

<tr>

<td>Dry ice

</td>

<td>Tetrachloroethylene

</td>

<td>−22

</td></tr>

<tr>

<td>Dry ice

</td>

<td>Carbon tetrachloride

</td>

<td>−23

</td></tr>

<tr>

<td>Dry ice

</td>

<td>1,3-Dichlorobenzene

</td>

<td>−25

</td></tr>

<tr>

<td>Dry ice

</td>

<td><i>o</i>-Xylene

</td>

<td>−29

</td></tr>

<tr>

<td>Dry ice

</td>

<td><i>m</i>-Toluidine

</td>

<td>−32

</td></tr>

<tr>

<td>Dry ice

</td>

<td>Acetonitrile

</td>

<td>−41

</td></tr>

<tr>

<td>Dry ice

</td>

<td>Pyridine

</td>

<td>−42

</td></tr>

<tr>

<td>Dry ice

</td>

<td><i>m</i>-Xylene

</td>

<td>−47

</td></tr>

<tr>

<td>Dry ice

</td>

<td><i>n</i>-Octane

</td>

<td>−56

</td></tr>

<tr>

<td>Dry ice

</td>

<td>Isopropyl ether

</td>

<td>−60

</td></tr>

<tr>

<td>Dry ice

</td>

<td>Acetone

</td>

<td>−78

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td>Ethyl acetate

</td>

<td>−84

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td><i>n</i>-Butanol

</td>

<td>−89

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td>Hexane

</td>

<td>−94

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td>Acetone

</td>

<td>−94

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td>Toluene

</td>

<td>−95

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td>Methanol

</td>

<td>−98

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td>Cyclohexene

</td>

<td>−104

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td>Ethanol

</td>

<td>−116

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td><i>n</i>-Pentane

</td>

<td>−131

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td>Isopentane

</td>

<td>−160

</td></tr>

<tr>

<td>Liquid N<sub>2</sub>

</td>

<td>(none)

</td>

<td>−196

</td></tr></tbody></table>

</div>

<div class="mw-heading mw-heading3"><h3 id="Water_and_ice_baths">Water and ice baths</h3></div>

<p>A bath of ice and water will maintain a temperature 0 °C, since the <a href="Melting_point" title="Melting point">melting point</a> of water is 0 °C. However, adding a salt such as <a href="Sodium_chloride" title="Sodium chloride">sodium chloride</a> will lower the temperature through the property of <a href="Freezing-point_depression" title="Freezing-point depression">freezing-point depression</a>. Although the exact temperature can be hard to control, the weight ratio of salt to ice influences the temperature:

</p>

<ul><li>−10 °C can be achieved with a 1:2.5 mass ratio of calcium chloride hemihydrate to ice.</li>

<li>−20 °C can be achieved with a 1:3 mass ratio of sodium chloride to ice.</li></ul>

<div class="mw-heading mw-heading3"><h3 id="Dry_ice_baths_at_−78_°C">Dry ice baths at −78 °C</h3></div>

<p>Since dry ice will <a href="Sublimation_(phase_transition)" title="Sublimation (phase transition)">sublime</a> at −78 °C, a mixture such as acetone/dry ice will maintain −78 °C. Also, the solution will not freeze because acetone requires a temperature of about −93 °C to begin freezing.

</p>

<div class="mw-heading mw-heading3"><h3 id="Safety_recommendations">Safety recommendations</h3></div>

<p>The <a href="American_Chemical_Society" title="American Chemical Society">American Chemical Society</a> notes that the ideal organic solvents to use in a cooling bath have the following characteristics:

</p>

<ol><li>Nontoxic vapors.</li>

<li>Low viscosity.</li>

<li>Nonflammability.</li>

<li>Low volatility.</li>

<li>Suitable freezing point.</li></ol>

<p>In some cases, a simple substitution can give nearly identical results while lowering risks. For example, using dry ice in <a href="2-propanol" class="mw-redirect" title="2-propanol">2-propanol</a> rather than acetone yields a nearly identical temperature but avoids the volatility of acetone (see <a href="#Further_reading">§ Further reading</a> below).

</p>

<ul><li><a href="List_of_cooling_baths" title="List of cooling baths">List of cooling baths</a></li>

<li><a href="Pumpable_ice_technology" title="Pumpable ice technology">Pumpable ice technology</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite id="CITEREFLeeJensen2000" class="citation journal cs1">Lee, Do W.; Jensen, Craig M. (2000). <span class="id-lock-subscription" title="Paid subscription required"><a rel="nofollow" class="external text" href="http://jchemed.chem.wisc.edu/Journal/issues/2000/May/abs629.html">"Dry-Ice Bath Based on Ethylene Glycol Mixtures"</a></span>. <i><a href="J._Chem._Educ." class="mw-redirect" title="J. Chem. Educ.">J. Chem. Educ.</a></i> <b>77</b> (5): 629. <a href="Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2000JChEd..77..629J">2000JChEd..77..629J</a>. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fed077p629">10.1021/ed077p629</a>.</cite></span>

</li>

<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://chemtips.wordpress.com/2015/02/09/methanolwater-mixtures-make-great-cooling-baths/">Methanol/Water mixtures make great cooling baths</a>. Chemtips.wordpress.com. Retrieved on 2015-02-23.</span>

</li>

<li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://chemtips.wordpress.com/2015/02/23/the-ridiculously-thorough-guide-to-making-a-meohwater-bath/">The ridiculously thorough guide to making a MeOH/Water bath</a>. Chemtips.wordpress.com. Retrieved on 2015-02-23.</span>

</li>

<li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://chemwiki.ucdavis.edu/VV_Lab_Techniques/Cooling_baths">Cooling baths – ChemWiki</a>. Chemwiki.ucdavis.edu. Retrieved on 2013-06-17.</span>

</li>

</ol></div></div>

<div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2></div>

<ul><li><cite id="CITEREFJonathan_M._PercyChristopher_J._MoodyLaurence_M._Harwood1998" class="citation book cs1">Jonathan M. Percy; Christopher J. Moody; Laurence M. Harwood (1998). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/experimentalorga0002harw"><i>Experimental Organic Chemistry: standard and microscale</i></a></span>. <a href="Blackwell_Publishing" class="mw-redirect" title="Blackwell Publishing">Blackwell Publishing</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-632-04819-9</bdi>.</cite></li>

<li><cite id="CITEREFWilfred_Louis_Florio_ArmaregoChristina_Li_Lin_Chai2003" class="citation book cs1">Wilfred Louis Florio Armarego; Christina Li Lin Chai (2003). <i>Purification of Laboratory Chemicals</i> (5th ed.). <a href="Butterworth-Heinemann" title="Butterworth-Heinemann">Butterworth-Heinemann</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-7506-7571-0</bdi>.</cite></li>

<li><cite id="CITEREFKenneth_P._Fivizzani2003" class="citation book cs1">Kenneth P. Fivizzani (2003). <i>Safety in Academic Chemistry Lab, by American Chemical Society, Volume 1: Accident Prevention for College and University Students</i> (7th ed.). <a href="American_Chemical_Society" title="American Chemical Society">American Chemical Society</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9780841238633</bdi>.</cite></li></ul>

<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><cite id="CITEREFCarter_Research_Group" class="citation web cs1">Carter Research Group. <a rel="nofollow" class="external text" href="http://oregonstate.edu/dept/chemistry/carter/cooling-bath-table">"Cooling Baths"</a>. <a href="Oregon_State_University" title="Oregon State University">Oregon State University</a>.</cite></li>

<li><cite id="CITEREFA._J._Meixner" class="citation web cs1">A. J. Meixner; et al. <a rel="nofollow" class="external text" href="http://www2.uni-siegen.de/~pci/versuche/english/v105-2.html">"10.5.2 Different Freezing Mixtures"</a>. <a href="University_of_Siegen" title="University of Siegen">University of Siegen</a>.</cite></li></ul></div><div><div class="zim-footer">

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