ID-62
Success! ID-62 with a separate PG solution works! I mixed them and tried it, with perfect results on Foma RC. I developed for 2 minutes at room temperature, and blacks are a hint darker than what Liquidol produced: densities were 1.91 vs 1.87.
The hydroquinone and phenidone are dissolved in propylene glycol (PG), and the rest are in the usual stock solution.
If these two solutions are stored in glass or PET bottles, and the PG solution kept refrigerated, I suspect they will last a couple of years (based on my experiences with other concentrates).
Here's what I mixed:
PG Solution
Propylene glycol (hot: 75-80 C) ..... 40 ml
Hydroquinone ................................ 12 g
Phenidone ...................................... 0.5 g
Propylene glycol to make ............... 50 ml
Stock Solution
Water .............................................. 800 ml
Na2EDTA ........................................ 4 g (mix this first to avoid precipitates when adding alkalis below)
Sodium sulfite, anh ......................... 50 g
Sodium carbonate, anh .................. 60 g
Potassium bromide ......................... 2 g
Benzotriazole .................................. 0.2 g
To Make 400 ml of Working Solution
Stock solution ................................. 100 ml
PG solution ..................................... 5 ml
Water to .......................................... 400 ml
The EDTA is needed only if you'll be using tap water; it's not needed for distilled water.
My chemicals are 8-10 years old, and some are suspect because they were stored in bottles made of HDPE instead of glass or PET. The Phenidone turned light orange when dissolved in PG, making me suspect that my old PG has some water in it. When mixed with stock solution, the orange vanished because the sulfite restored the phenidone.
I don't have a hot plate, so I used a strip of scrap sheet aluminum on the stove.
I turn on only the left burner, at a medium-low setting, and the temperature of the sheet metal ranges from too hot (left) to too cool (right). I slide the beaker to the left or right to maintain correct temperature. I call this arrangement "the poor man's hot plate." I stir with the thermometer, so I can constantly monitor the temperature of the PG solution.