Ask A Scientist© Chemistry Archive

name       joe
status     other
age        30s

Question - I am intersted in endothermic mixtures. especially any that
are relatively non toxic and inexpensive. where can i find lists of
various mixtures that will result in a cooling effect, ratios of
chemicals for best results, etc.

what are the reaction products in an ammonium nitrate and water reaction?
(been a long time since college chemistry) how could resulting products be
disposed of safely?
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The Handbook of Chemistry and Physics, published by the Chemical Rubber 
Company, [ISBN-0-8493-0463-6], which probably can be found in the 
reference section of most libraries, has a limited list of heats of 
solution. Look up:
"Heat of solution, selected compounds" in the index.

Some endothermic heats of solution of some relatively non-toxic, 
inexpensive, and probably available salts in kilo-calories/mole are:
NH4Cl = 3.533, NH4NO3 = 6.140, KNO3 = 8.340

All of these dissolve to form their respective ions: NH4(+1), Cl(-1), 
K(+1), and NO3(-1)

Small amounts of all of these salts could be disposed of in the sink.

The maximum cooling will probably be obtained by mixing as much as 
possible, until the water solutions are saturated.
V. Calder
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Ammonium nitrate and water is probably your best bet. The baking soda and
acid reaction is also endothermic, but it's an actual chemical reaction and
not just a mixing phenomenon. I don't know where you can find a list of
endothermic reactions.

When ammonium nitrate is mixed with water, all that happens is that the
ammonium nitrate dissolves in the water. No new products are formed, unless
you count dissociated ammonium ions and nitrate ions. As for safe disposal,
dilute it with water and use it to fertilize your garden. Don't dump too
much at once, though, as any nitrate running into a stream can cause
eutrophication.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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