Thanks!

In some sites I seen this formula with 150 g Potassium Carbonate only, and if you are interested, I know some similar developer:

Riap PB-1k (russian)

Sodium Sulphite (anh) . . . . . . . . .150 g
Hydroquinone . . . . . . . . . . . . . . 32 g
Potassium Carbonate . . . . . . . . . .150 g
Phenidone . . . . . . . . . . . . . . . . . 0,8 g
Potassium Bromide . . . . . . . . . . . 6 g
Water to . . . . . . . . . . . . . . . . . 1 litre

1+9