i am a total newbie here....i understand basic principles like supercooling, phase change, etc, but otherwise a total dummy, i have equivalent to 1st yr university in chem, but that was a long, long time ago. so go easy on me. i am trying to find out the difference btwn sodium acetate trihydrate (used in handwarmers), and anhydrous sodium acetate (used as de-icer). is it the same thing? the former seems to be kind of expensive, sold by the gram, the latter seems to be cheaper, sold by the ton. specifically, i guess i want to know, does the latter share the trait to be easily supercooled? the reason i ask, is i like the potential for sodium acetate trihydrate to "store" heat, and would like to do this in large quantities, but it seems too expensive to do this on practical terms, but anhydrous s.a. seems a lot cheaper, can it do the same? i also would like to know, am i naiive here to think that you can store the heat of summer to be busted out of some huge underground storage facility in the dead of winter? (i know that you would have to separate into small quantities or otherwise you use it all in one enormous reaction.) will it remain in it's supercooled state indefinitely, as long as you don't provide a nucleation point (physically disturbing it, contaminants, etc)? on a similar note, could one do a similar opposite thing with ammonium nitrate? i am an architecture student, by the way, obsessed with the idea of saving the world thru green architecture.