10% solutions

I was thinking of making up 10% solutions for some of my ingredients to make the process of measuring small amounts a little easier. Is this posssible or advisable with Metol, Hydroquinone and Phenidone or would oxidisation be a problem here. I'm thinking it probably would, but I'd value the forums suggestions. Is there a list somewhere of the chemicals that can be successfully used in this way? Regards, Blights.

I keep percentage solutions of Hydroquinone, Pyrogallol, Pyrocatechcol and Phenidone - all dissolved in Propylene Glycol. They have a long shelf life. None of these chemicals keep well when dissolved in water, however.

Metol is not very soluble in Propylene Glycol but does dissolve in Triethanolamine.

I keep a percentage solution of Metol base using Patrick Gainer's method (Metol/Triethanolamine/ and a bit of water). Do an Apug search on Gainer and Metol.