Now let's play with p-aminophenol.
Paraminophenol is not very soluble in water. The potassium aminophenolate is quite soluble and a very active developer. Before we knew it as the proprietary Rodinal, Hurter and Driffield referred to a developing agent named rodinal, which I think might have been potassium aminophenolate. We can make a 0.05 molar solution of this rodinal from 0.05 moles of potassium hydroxide and 0.05 moles of p-aminophenol base, add to it 0.05 moles of ascorbic acid and another 0.05 moles of sodium or potassium hydroxide and some borax and end up with a kinder and gentler Rodinal expedient. Maybe.
This recipe is:
5.45 grams of p-aminophenol base
8.8 grams ascorbic acid
28 grams of sodium metaborate
Water to 1 liter.
( the 28 grams of metaborate includes the equivalent of 4 grams of sodium hydroxide and a bunch of borax.
I doubt that you will want to use this stuff full strength.
You can make a 2-part concentrated developer as follows.
Dissolve 22 grams p-aminophenol base and 35.2 grams ascorbic or erythorbic acid in about 400 ml propylene glycol. Add glycol to bring volume to 500 ml. This is solution A.
Dissolve 110 grams of sodium metaborate in water to make 500 ml. This is solution B. If you do not have metaborate, use 16 grams of sodium hydroxide or 22 grams of potassium hydroxide plus 76 grams of borax
Mix equal parts of A and B in water. A typical dilution would be 1:1:25. A typical development time for FP4+ would be 8 minutes at 70 F.