well today I tried the experiment with sodium acetate and water but it didn't work.

I used sodium acetate from a chemistry lab (so it is pure...), I put sodium in boiling distilled water for a super-saturated solution: 160 gr in 30 ml of water and I left it on the heater for some minutes.

i put the solution in fridge but the solution crystallize in few minutes instead of stay fluid and i cannot use for make instantly "hot ice"...

where I made a mistake?!?

 

thanks a lot!

I think that you need to make sure there are no nuclation points anywhere (like undisolved crystals in the supersaturate, or scratches in the glassware). However, I haven't actually done this experiment myself, but have seen it done and own warming devices that use he reaction for heat. You can reverse it by heating it up and re-disolving.

 

Finally, which is what moved me to post, is that you shouldn't assume that your reagents are pure simply because they come from a chemistry lab. They could become contaminated anyhow. In this instance, though, I'm not sure how it would effect the reaction.

if you're having trouble with it crystallising too soon, just add bit of extra water, and make sure all your glassware is clean and free of cracks and dents

Filter the solution while it's hot (obviously, this might be tricky). That way you remove dust and such that can act as a nucleation point.

A rapid cooling is required for supersaturated solution.

thanks a lot! I'll try all the suggestion and I hope to come with something positive!