Looking for a safe exothermic reaction

Question

Is there an exothermic reaction which produces 1 to 2 minutes of heat at around 175 degrees Fahrenheit, no toxic gasses and is considered to be more or less safe?

Safe is a matter of scale. The reactions mentioned in the other answers are all "safe" on small scales, say less than 100 mL or 100 g. What are you planning on heating? How big is it? — Ben Norris, Oct 20 '12 at 12:36

score 5 · Answer 1 · edited Apr 13 '17 at 12:57

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Crystallisation of supersaturated sodium acetate is a good one, as seen in my answer here.

Another is the reaction of water with calcium oxide, which is commonly seen in self-heating coffee and soup cans. This reaction can get very hot, though.

edited Apr 13 '17 at 12:57

Community

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answered Oct 19 '12 at 12:58

Richard Terrett

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score 2 · Answer 2 · answered Oct 19 '12 at 11:54

Simplest thing that comes to my mind is dissolving sodium or potassium hydroxide in water, and/or neutralizing it. Both steps are exothermic, and also rather safe (given that you don't just blindly throw things together). Should become hot enough, I'd guess.

score 1 · Answer 3 · answered Jun 09 '16 at 21:24

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Use a mix of ammonium chloride, sodium nitrite and acetic acid. It produces water, nitrogen and heat.

answered Jun 09 '16 at 21:24

Fausto Arinos Barbuto

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Could you elaborate? Maybe add reaction equation – Mithoron Jun 09 '16 at 23:15
"Ammonium chloride" and "sodium nitrite" are actually aqueous solutions of those salts. The reaction is $$NH_4Cl + NaNO_2 --> N_2 + 2H_2O + NaCl$$. – Fausto Arinos Barbuto Jun 10 '16 at 03:09

Looking for a safe exothermic reaction

3 Answers3