CWU Chemistry Laboratory Specific Standard Operating Procedure
SOP for: (check one)
Process
Hazardous Chemical
Hazard Class of Chemicals
Name of Procedure: Preparing a cooling bath for a low-temperature reaction
Applies to Lab (name): Chamberland Research Group
SCI Room #: 313
Prepared By: Brandon Petersen, Stephen Chamberland
Date: 12/2/11
Revision: 8/31/12
Special Notifications:
This SOP describes how to prepare a low-temperature bath needed when conducting a reaction below room
temperature.
Hazard Description:
Gaseous and liquid acetone and isopropyl alcohol are flammable. Low-temperature baths can cause burns to the skin.
Protective Equipment:
- Lab coat
- Protective wrap-around goggles
- Thermally insulated gloves
- Long pants
- Close-toed shoes
Engineering Controls:
Prepare low-temperature baths in a working fume hood. Set low-temperature baths on a sturdy, stable, and flat surface
such as the floor of the fume hood or on a lab jack or stir plate that sits on the floor of the fume hood.
Special Handling or Storage Requirements:
Care must be taken when preparing and moving low-temperature baths to avoid skin contact with the cold liquid.
Spill Response Procedure:
Do not attempt to clean up any spill of cryogenic liquid. Spilled slurry from a low-temperature bath may be allowed to
evaporate/sublime in the fume hood.
Decontamination/Waste Disposal:
After using the cold bath, the excess liquid may be warmed to room temperature and poured into the organic solvent
waste container.
Special Emergency Procedures:
If skin or eye(s) comes in contact with a cryogenic liquid, run the area of skin under cool or warm water for fifteen
minutes (do not use hot or cold water). DO NOT RUB OR MASSAGE AFFECTED AREAS— this can cause further
tissue damage. Refer to the SDS for the solvent used for any specific instructions. Where medical attention is required,
ensure to bring along the SDS(s) of chemical(s) to aid medical staff in proper diagnosis and treatment.
Procedure may be performed after normal working hours (M-F, 8-5)?
Procedure may be left unattended?
Yes
Yes
No
No
Step by Step Procedure:
Prepare low-temperature baths in an insulated dewar flask to keep the mixture cold. Doing so also prevents ice buildup
on the exterior of a non-insulated bath, such as a crystallizing dish or beaker, caused by condensation and freezing of
water vapor from the air.
The most common low-temperature baths needed in the Chamberland lab.
Temperature
Mixture Composition
0 °C
Ice + water
−20 °C
Equal amounts of ice and solid NaCl. The actual temperature obtained will depend on how finely
crushed and well mixed the components are, and could be as high as -10 °C. A dewar is recomended.
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CWU Chemistry Laboratory Specific Standard Operating Procedure
Brine/ dry ice produces an identical mixture.
−40 °C
Acetonitrile/dry ice. Put the acetonitrile into the Dewar with your thermocouple, slowly add dry ice until
you hit your desired temperature. Don't add too much dry ice or you'll freeze the MeCN solid.
−78 °C
Dry ice/acetone: Slowly adding acetone to crushed dry ice will minimize the amount of dry ice you need
to handle. Alternatively, you must slowly add dry ice to the acetone or the large volumes of carbon
dioxide produced will cause rapid bubbling and splashing of the cold liquid out of the dewar.
−100 °C
Dry ice / ethyl ether
−131 °C
liquid nitrogen / n-pentane
Less common low-temperature baths
Temperatures between -20 and -80° can be obtained using varied mixtures of ethylene glycol and ethanol over dry ice.
A little more detailed list taken from the Hoveyda group website at Boston College.
Temperature
Mixture Composition
13 °C
p-Xylene / dry ice
12 °C
Dioxane / dry ice
6 °C
Cyclohexane / dry ice
5 °C
Benzene / dry ice
2 °C
Formamide / dry ice
0 °C
Crushed Ice
−5 to −20 °C
Ice / Salt
−10.5 °C
Ethylene Glycol / dry ice
−12 °C
Cycloheptane / dry ice
−15 °C
Benzyl alcohol / dry ice
−22 °C
Tetrachloroethylene / dry ice
−22.8 °C
Carbon Tetrachloride / dry ice
−25 °C
1,3-Dichlorobenezene / dry ice
−29 °C
o-Xylene / dry ice
−32 °C
m-Toluidine / dry ice
−41 °C
Acetonitrile / dry ice
−42 °C
Pyridine / dry ice
−47 °C
m-Xylene / dry ice
−56 °C
n-Octane / dry ice
−60 °C
Isopropyl Ether / dry ice
−78 °C
Acetone / dry ice
−78 °C
Butyl Acetate / dry ice
−83 °C
Propyl Amine / dry ice
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CWU Chemistry Laboratory Specific Standard Operating Procedure
−83.6 °C
Ethyl Acetate / Liq N2
−89 °C
n-Butanol / Liq N2
−94 °C
Hexane / Liq N2
−94.6 °C
Acetone / Liq N2
−95.1 °C
Toluene / Liq N2
−98 °C
Methanol / Liq N2
−100 °C
Ethyl Ether / dry ice
−104 °C
Cyclohexane / Liq N2
−116 °C
Ethanol / Liq N2
−116 °C
Ethyl Ether / Liq N2
−131 °C
n-Pentane / Liq N2
−160 °C
Isopentane / Liq N2
−196 °C
Liq N2
Example: Step-by-step preparation of a low-temperature (−78 °C bath) using dry ice and acetone. Dry ice and
isopropyl alcohol can also be used to prepare a viscous slurry that holds the low temperature longer.
1. Support the reaction flask using a secure metal three-prong clamp attached to the metal bars in the hood.
2. Place a dewar flask on a stirring plate and lower the reaction flask into the dewar. Keep the stir bar in the reaction
flask as close to the surface of the stir plate as possible to enable optimum stirring.
3. Scoop crushed, powdered dry ice into the dewar so that it surrounds the reaction flask and reaches the level of the
liquid/solution in the flask.
4. Using a squirt bottle, add acetone to the dry ice to produce a slurry. Confirm that the slurry reaches −78 °C using a
low-temperature thermometer. Secure the thermometer using a metal three-prong clamp attached to the sturdy
metal bars in the fume hood.
5. Add more dry ice or acetone as needed should the slurry temperature rise above −78 °C.
Approved By (PI) : Stephen Chamberland, Ph.D.
Date: 8/31/12
PI Signature: ___________________________________________________
Date: ______________
EH&S Signature: ________________________________________________
Date: ______________
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