For what it is worth, it is handy to keep various chemicals in stock solutions as is done in most chemical laboratories. I'm keeping amidol, phenidone, ascorbic acid, pyrogallol, hydroquinone and catechiol in propylene glycol. The amidol and phenidone are in 1% solutions, 1 gram/ 100 ml, and the others are in 10% solutions. Amidol keeps in glycol solution, as does phenidone and the others. I can mix and match for experimental purposes, but it is convenient as well when I have become staid in my concoctions. (If that ever happens.) The chemicals that are dangerous, including amidol, pyro, catechol and hydroquinone, are also safer IMHO in the gkycol solution than in powder that can become airborne while measuring. Mixing once is better than mixing for each use. You can buy amidol 10 grams at a time to make a liter of solution. I have found amidol to be in some ways a good substitute for phenidone, but every time I open the container of dry powder, I worry. Of course, I can still spill the solution, but there's less chance of it getting into the air than the powder, especially when it is in glycol. Some of these things might be safer with the extra viscosity of glycerin instead of glycol. As usual, these materials dissolve easier in hot glycol, but it need not be as hot as I once thought.