I opened one cold pack after I got suspicious when one didn't get as cold as I thought it would get. Ingredients were listed as ammonium nitrate and
I think it was CAN or a mixture of AN and some calcium. I dissolved in methanol and in water and in both cases a lot of calcium was left behind,
especially with the methanol. An excess of methanol was used by 200ml to ensure total dissolution of the AN. Of the 123g of prills, about 48 grams
was a calcium product left behind.
I did this with 3 different store brand cold packs, CVS, Walgreens and a generic store brand, and all had the same result and the amount of prills
varied by about 10% in each pack, so their measurement isn't always exact.
There are some brands that state CAN as the ingredient but the ones I bought specifically said ammonium nitrate alone.
IDK if calcium ammonium nitrate dissolves in water or methanol, or if the process of dissolving it/hydrating it does something to change the bond
between the calcium and the ammonium nitrate.
I haven't done anything with the calcium by product but am interested in what it is, if it is the carbonate (which I would think it kind of has to be
at this point, as if it was the hydroxide - which would have had to come from a CaO + NH4NO3 combination that may result in the poor endothermic
results??)
I know that the CAN is not a good cold pack substitute and I think even anhydrous sodium acetate produces a better, deeper cold than this did as it
was on par with calcium nitrate in the cooling effect. happyfooddance - 28-12-2017 at 07:12
Did you try reacting it with an acid? It might be something more inert, like sililca...mayko - 28-12-2017 at 08:04
Does the residue dissolve in fresh water? (ie, is it actually insoluble, or just oversaturated?)
Effervesence on addition of acid would confirm calcium carbonate. Also, I'd expect calcium hydroxide to precipitate upon the addition of sodium
hydroxide to a concentrated calcium ammonium nitrate solution, as well as the formation of ammonia and sodium nitrate. You might even be able to get
calcium carbonate to precipitate by bubbling CO2 through the CAN.
Calorimetry might also be useful, but I'd try a few test tube experiments first. RogueRose - 28-12-2017 at 14:07
I did an acid and water test with the white residue.
31.45% HCl - turned yellow immediately (acid was clear) and bubbles at a constant rate - not vigerous but constant steady small bubbles. slight Cl2
smell. Solution stayed yellow -
30% acetic acid - no reaction
31% H2SO4 - Same bubbling as HCl, white fluffy "slime", no smell.
5% vinegar - no reaction
hot water - no reaction
cold water - no reaction
[Edited on 28-12-2017 by RogueRose]MrHomeScientist - 28-12-2017 at 14:20
You could also test for calcium with a soluble sulfate, like sulfuric acid or Epsom salt. A white precipitate indicates calcium (or barium, I
suppose).RogueRose - 28-12-2017 at 15:26
You could also test for calcium with a soluble sulfate, like sulfuric acid or Epsom salt. A white precipitate indicates calcium (or barium, I
suppose).
I tried 31% H2SO4 as well as plain 5% vinegar (IDK if my 30% AA was "good") and the H2SO4 reacted similarly to the HCl but stayed white. The vinegar
did nothing.
Now just to make this clear, I'm testing what was left behind from the methanol extraction, which is a solid white precipitate. I think some of it
did dissolve in the methanol while it was hot but when I poured it into the filtration funnel, it crashed out pretty quickly when the temp dropped a
few degrees, along with the "AN" crystals.
