20:
311:
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
47:, 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
315:
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.
97:
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.
768:
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.
284:
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
967:
944:
898:
94:, etc.), which transfers heat between the bath and the vessel; (3) an additive to depress the melting point of the solid/liquid system.
990:
979:
Safety in
Academic Chemistry Lab, by American Chemical Society, Volume 1: Accident Prevention for College and University Students
1042:
886:
765:
301:
800:
In some cases, a simple substitution can give nearly identical results while lowering risks. For example, using dry ice in
1052:
748:. Although the exact temperature can be hard to control, the weight ratio of salt to ice influences the temperature:
982:
777:
745:
1012:
822:
959:
817:
1025:
936:
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78:) — but most commonly the term refers to (b) a mixture of 3 components: (1) a cooling agent (such as
804:
rather than acetone yields a nearly identical temperature but avoids the volatility of acetone (see
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848:
780:
notes that the ideal organic solvents to use in a cooling bath have the following characteristics:
1008:
1021:
986:
963:
940:
910:
56:
52:
869:
752:−10 °C can be achieved with a 1:2.5 mass ratio of calcium chloride hemihydrate to ice.
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24:
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Cooling baths are generally one of two types: (a) a cold fluid (particularly
755:−20 °C can be achieved with a 1:3 mass ratio of sodium chloride to ice.
736:
A bath of ice and water will maintain a temperature 0 °C, since the
293:
19:
289:
91:
79:
873:
927:
Jonathan M. Percy; Christopher J. Moody; Laurence M. Harwood (1998).
297:
71:
18:
300:
span the −128 °C to 0 °C temperature range. Dry ice
31:(−78 °C) the temperature of which is being monitored by a
83:
75:
954:
Wilfred Louis Florio
Armarego; Christina Li Lin Chai (2003).
899:
The ridiculously thorough guide to making a MeOH/Water bath
931:
Experimental
Organic Chemistry: standard and microscale
740:
of water is 0 °C. However, adding a salt such as
744:will lower the temperature through the property of
928:
901:. Chemtips.wordpress.com. Retrieved on 2015-02-23.
889:. Chemtips.wordpress.com. Retrieved on 2015-02-23.
842:
840:
838:
86:); (2) a liquid "carrier" (such as liquid water,
27:. Both flasks are submerged in a dry ice/acetone
913:. Chemwiki.ucdavis.edu. Retrieved on 2013-06-17.
887:Methanol/Water mixtures make great cooling baths
849:"Dry-Ice Bath Based on Ethylene Glycol Mixtures"
16:Liquid mixture used to maintain low temperatures
8:
101:Mixed solvent cooling baths (% by volume)
324:
99:
834:
847:Lee, Do W.; Jensen, Craig M. (2000).
7:
1022:"10.5.2 Different Freezing Mixtures"
956:Purification of Laboratory Chemicals
805:
23:A typical experimental setup for an
326:Traditional cooling bath mixtures
14:
1:
977:Kenneth P. Fivizzani (2003).
51:, to remove solvents using a
59:below room temperature (see
1020:A. J. Meixner; et al.
280:Mixed-solvent cooling baths
1069:
308:is used for colder baths.
983:American Chemical Society
778:American Chemical Society
746:freezing-point depression
320:Traditional cooling baths
911:Cooling baths – ChemWiki
796:Suitable freezing point.
334:Organic solvent or salt
1013:Oregon State University
1007:Carter Research Group.
823:Pumpable ice technology
760:Dry ice baths at −78 °C
35:(the wire on the left).
806:§ Further reading
772:Safety recommendations
304:at −78 °C, while
36:
1043:Laboratory techniques
960:Butterworth-Heinemann
818:List of cooling baths
450:Carbon tetrachloride
22:
1026:University of Siegen
937:Blackwell Publishing
461:1,3-Dichlorobenzene
439:Tetrachloroethylene
292:, while mixtures of
866:2000JChEd..77..629J
764:Since dry ice will
732:Water and ice baths
327:
102:
1053:Cooling technology
403:Salts (see: left)
325:
100:
55:, or to perform a
37:
969:978-0-7506-7571-0
946:978-0-632-04819-9
874:10.1021/ed077p629
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106:% Glycol in EtOH
57:chemical reaction
53:rotary evaporator
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1016:
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981:(7th ed.).
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958:(5th ed.).
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790:Nonflammability.
784:Nontoxic vapors.
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921:Further reading
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312:respectively).
306:liquid nitrogen
286:ethylene glycol
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88:ethylene glycol
68:liquid nitrogen
61:Kinetic control
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500:Acetonitrile
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662:Cyclohexene
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370:Cyclohexane
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283:
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49:distillation
44:
41:cooling bath
40:
38:
33:thermocouple
29:cooling bath
28:
707:Isopentane
489:-Toluidine
1048:Cryogenics
1037:Categories
860:(5): 629.
829:References
802:2-propanol
392:Formamide
337:Temp (°C)
119:Temp (°C)
116:O in MeOH
109:Temp (°C)
74:, or even
693:-Pentane
648:Methanol
592:-Butanol
511:Pyridine
406:0 to −40
812:See also
808:below).
715:Liquid N
701:Liquid N
684:Liquid N
676:Ethanol
670:Liquid N
656:Liquid N
642:Liquid N
634:Toluene
628:Liquid N
620:Acetone
614:Liquid N
600:Liquid N
583:Liquid N
569:Liquid N
561:Acetone
558:Dry ice
547:Dry ice
539:-Octane
533:Dry ice
525:-Xylene
519:Dry ice
508:Dry ice
497:Dry ice
483:Dry ice
475:-Xylene
469:Dry ice
458:Dry ice
447:Dry ice
436:Dry ice
425:Dry ice
411:Liquid N
389:Dry ice
381:Benzene
378:Dry ice
367:Dry ice
359:Dioxane
356:Dry ice
348:-xylene
342:Dry ice
302:sublimes
294:methanol
45:ice bath
862:Bibcode
766:sublime
721:(none)
606:Hexane
290:ethanol
92:acetone
80:dry ice
989:
966:
943:
245:−12.5
133:−97.6
724:−196
710:−160
696:−131
679:−116
665:−104
298:water
270:100%
264:100%
259:−5.5
147:−128
72:water
987:ISBN
964:ISBN
941:ISBN
776:The
651:−98
637:−95
623:−94
609:−94
595:−89
578:−84
564:−78
553:−60
542:−56
528:−47
514:−42
503:−41
492:−32
478:−29
464:−25
453:−23
442:−22
431:−15
420:−12
400:Ice
362:+12
351:+13
296:and
288:and
267:−17
256:90%
253:−21
250:90%
242:80%
239:−28
236:80%
231:−20
228:70%
225:−32
222:70%
217:−36
214:60%
211:−41
208:60%
203:−47
200:50%
197:−52
194:50%
189:−64
186:40%
183:−60
180:40%
175:−72
172:30%
169:−66
166:30%
161:N/A
158:20%
155:−72
152:20%
144:14%
141:−76
138:10%
127:−78
870:doi
395:+2
384:+5
373:+6
130:0%
124:0%
112:% H
84:ice
82:or
76:air
63:).
43:or
1039::
1024:.
1011:.
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962:.
939:.
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858:77
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590:n
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571:2
537:n
523:m
487:m
473:o
413:2
346:p
114:2
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