Author Topic: ????ICE BATH????  (Read 1074 times)

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xtc4fun

  • Guest
????ICE BATH????
« on: August 31, 2003, 11:20:00 PM »
k first swim would like to know what is an ice bath that u hear so much about? is it ice in water in a bowl? if not then what is it?? ice in acetone? any help would be great

pHarmacist

  • Guest
Yes, you are right...
« Reply #1 on: August 31, 2003, 11:28:00 PM »
It's often ice in water, but you can add some NaCl(s) (plain salt) to the 'bowl' just to drop the T even more, somwhere around -20 Celsius... It's actually quite effective.


Blind_Angel

  • Guest
Other Cooling baths
« Reply #2 on: August 31, 2003, 11:46:00 PM »
There are also other way here is some (quoted from this

tread of BASF on ScienceMadness forum

(http://www.sciencemadness.org/talk/viewthread.php?tid=897)) :


1)The most simple cooling mixture is probably NaCl + crushed ice(-20°C).

It has to be mentioned that the parts of the ice are ideally not bigger than 0.5-1cm diameter, or a significant decrease of cooling-performance has to be accepted.

It is also important to weigh the mixing-portions of ice and salt, although a 50:50 ratio might be a good approximation.
The mixing-ratios can be found in various books about preparative chemistry, although i think the solubility at 0°C can be taken as a basis for calculation of the ratios.

2)The most cost-effective of the mixtures is the ammonium-nitrate-ice-bath. KAS 27-fertilizer is working well, although recrystallized ammonium nitrate is much better because there are no insoluble additives. So far i have not found the mix tabulated, but i think at least about -25°C are possible.
This one is a good choice for nitrations taking place at below +15°C, it allows an acceptable rate of addition of reactants.
A good idea is to take an aluminum container because of the good heat conduction...the work with thick-walled round-bottomed glass-flasks is frustating.

3)One of the best(in my opinion) cooling mixtures is 66% H2SO4 with crushed ice (55:45). The temp in the bath sinks to -37°C.
I am not sure if the conc. of industrial waste-sulfuric acid was about 60% or if it was 30%("Dünnsäure"; Ger).
A big advantage is the low viscousity of the mix. It can be stirred with a bigger magnetic stirring bar for faster heat exchange.

4)Calcium chloride hexahydrate(not to mistake with dehydrated CaCl2, which is used in drying columns) with crushed ice.
Temp: -40°C

5)Quite expensive, but impressive is hydrated KOH with crushed ice.
Although i never tried that myself, -60°C are tabulated.




Thank goes to BASF




xtc4fun

  • Guest
thanks all
« Reply #3 on: September 01, 2003, 12:18:00 AM »
thanks for the info this is what i was lookin for:) thanks alot again..


acid_egg

  • Guest
Ice/Cooling baths
« Reply #4 on: September 01, 2003, 12:41:00 AM »
In case you need to go colder still.


It is often necessary to obtain temperatures below that of the laboratory. Finely crushed ice is used for maintaining the temperature at 0-5C : it is usually best  to use a slush of crushed ice with sufficient water to provide contact with the vessel to be cooled and to stir frequently.
For temperatures below 0C, the commonest mixture is an intimate mixture of common salt and crushed ice : a mixture of one part of common salt and three parts ice will theoretically produce a temperature of about -20C but, in practice, the ice salt mixture gives temperatures of -5C to -18C. Greater cooling may be obtained by the use of crystalline calcium chloride ; temperatures of -40 to -50C may be reached with five parts of CaCl2,6H2O and 3.5-4 parts of crushed ice.
If ice is temporarily unavailable, advantage may be taken of the cooling effect attending the solution of certain salts or salt mixtures in water. Thus a mixture produced by dissolving 1 part of NH4Cl and 1 part of NaNO3 in 1-2 parts water causes a reduction in temperature from 10C to -15 to -20C ; 3 parts of NH4Cl in 10 parts water from 13C to -15C ; 11 parts of Na2S2O3 in 10 parts of water from 11C to -8C ; and 3 parts of NH4NO3 in 5 parts of water from 13C to -13C.
Solid carbon dioxide (Dry Ice, Drikold) is employed when very low temperatures are required. If it is suspended in solvents, such as alcohol or a mixture of chloroform and carbon tetrachloride, temperatures down to -50C can be easily attained. Lower temperatures still are reached if intimate mixtures of solid carbon dioxide and organic solvent are employed : with ethyl alcohol, -72C; with diethyl ether, -77C; and with chloroform or acetone, -77C.




VOGEL (3rd ED.)

https://www.thevespiary.org/rhodium/Rhodium/chemistry/vogel3.html



RoundBottom

  • Guest
pumping
« Reply #5 on: September 01, 2003, 01:13:00 AM »
which of these are bad for pumps? for example, brine will corrode metal quickly, no?  specifically refering to those pond pumps or small utility pumps. 

and i always thought a large block of ice was better for cooling because it lasted longer.

what are those liquids that are used in lab recirculators?

don't forget to put those foam chips, or ping pong balls on top of the water to insulate it.


abolt

  • Guest
Aquarium
« Reply #6 on: September 01, 2003, 10:46:00 AM »
which of these are bad for pumps? for example, brine will corrode metal quickly, no?

RB, your local aqurium should have recirculation pumps for salt water aquariums. ;)


aleph

  • Guest
brine vs: metal
« Reply #7 on: September 01, 2003, 05:09:00 PM »
Yes, even stainless steel isn't rust-proof when long-term exposure to saltwater is concerned.  I think most saltwater recirculating pumps actually only allow the water to touch plastic parts.

Dry ice in acetone is sometimes used to cool branding irons such that cold produces the brand on cattle, rather than heat.  Ya gotta bee doing some serious shit to need that kind of cold in a chem lab.