Sciencemadness Discussion Board

cold compresses

Vexing - 26-5-2007 at 10:27

I recently heard that both Ammonium Nitrate and Urea are used in instant cold packs. Does anyone know of an easy test to differentiate between them?

Oxydro - 26-5-2007 at 11:08

Usually the safety label on the cold pack. Barring that, heat it - Urea will be melting (or maybe decomposing!) about 35 C colder than AN melts.

Vexing - 27-5-2007 at 10:51

Edit: I found an easy test, melting and see if it produces Nitrous oxide.

[Edited on 27-5-2007 by Vexing]

olmpiad - 2-6-2007 at 10:04

I suppose you could crystallize the compound and compare the structure of the two possibilities to the structure that you got.

Eclectic - 2-6-2007 at 10:29

Is it an either/or thing or maybe BOTH urea and ammonium nitrate?
I've made a liquid garden fertilizer from a 50/50 mix, and it dissolved faster and got colder than either one alone and only needed about 15% water to dissolve it all.

Swany - 2-6-2007 at 10:39

Check the pH of a solution containing them; urea is basic and ammonium nitrate is acidic.

olmpiad - 2-6-2007 at 15:59

Quote:
Originally posted by Eclectic
Is it an either/or thing or maybe BOTH urea and ammonium nitrate?
I've made a liquid garden fertilizer from a 50/50 mix, and it dissolved faster and got colder than either one alone and only needed about 15% water to dissolve it all.


When it's something being applied to one's skin, extreme cold is not always the best.

Vexing - 3-6-2007 at 08:29

It is Ammonium Nitrate. I tested a solution with Phenolphthalein. Just out of curiosity, how common is Urea in cold compresses?

olmpiad - 3-6-2007 at 15:57

Ive never found it