Get your hands on potassium sulphite or potassium metabisulphite (and react it with potassium hydroxide beforehand) if you want to make a high-sulphite concentrate.
I've made a very high phenidone-ascorbate concentrate, but using potassium ascorbate. React the AA prior with a potassium salt like KOH. Shouldn't need as much sulphite for preservative with high ascorbate content. If you want to add salicylic acid, just use supermarket aspirin, it will hydrolyse in solution to salicylate.
If then the only role left for sulphite is to act as a fine grain solvent. You could use a very small amount of potassium thiocyanate (as in a non-highlight clearing/non-reversal amount for the process times).
My current concentrate is a bit different I made is similar, 4-aminophenol, potassium ascorbate and CD-2, still good after over a year, with some floating precipitate (saturated solution, like this since fresh). It is 1+24 to 1+49 dilution (20 min for HP5+ etc at 1+49), produces a negative that has higher local contrast with better micro details, but prints on a higher grade filter for the same black to white range (good for high contrast subjects already printing at 0), has more accentuated grain though.
If you want a very high keeping life of concentrates, if you're going to split it into a 2 part solution anyway, making the part with the developing agents pH 4-6, with potassium metabisulphite and/or ascorbic acid etc, should increase the shelf life due to lower pH.
Last edited by Athiril; 07-28-2012 at 12:30 AM. Click to view previous post history.