Rodinal cannot be made from p-amino phenol hydrochloride, it has to be the free base. This can be made first from the hydrochloride. So the formula you quote is wrong.


Quote Originally Posted by Relayer View Post

I was found two different formula for EZ-Rodinal

1st early version found here:

Start with 700 ml water at room temperature.
Add 170 grams of anhydrous sodium sulfite, 14 grams sodium hydroxide, and stir till dissolved. Warming it a little won't hurt. Add 40 grams p-aminophenol (not the hydrochloride). It will not all dissolve. Add water to make 1 liter. When you transfer from the mixing vesel to storage, do not filter out the sediment. Use it like AGFA Rodinal.

2nd (latest) version from EZ-Rodinal article

To 400 ml water, add:
85 g anhydrous sodium sulfite.
40 g p-aminophenol base.
Stir well. Add
13.8 g sodium hydroxide or 19.2 g potassium hydroxide.
Add water to make 500 ml.

rewrite this formulas for 1l concentrate:

1st version
Sodium sulfite 170g
p-Aminophenol base 40g
Sodium hydroxide 14g
Water 1l

2nd version
Sodium sulfite 170g
p-Aminophenol base 80g
Sodium hydroxide 27.6g
Water 1l

easy to see that 2nd version have twice amount of p-Aminophenol. Compared to known Rodinal formula from

p-Aminophenol Hydrochloride 50 g
Potassium Metabisulfite 150 g
Sodium Hydroxide 100 g
Cold water to make 1L

while we mix all ingredient reaction describes next formulas

K2S2O5 + 2NaOH = K2SO3 + Na2SO3 + H2O
C6H4OHNH2.HCl + 2NaOH = C6H4ONaNH2 + NaCl + 2H2O

MW(C6H4OHNH2.HCl)=145.59, so formula contains 50/145.59=0.343M of p-Aminophenol Hydrochloride. For PAP base MW(C6H4OHNH2)=109.13. and amount of base will be 109.13*0.343M=37.48g. This is near the 50g in 1st version of EZ-Rodinal.
Amount of K2SO3+Na2SO3 is 1.35M. We need 1.35M*MW(Na2SO3)=1.35M*126.04=170g of Sodium sulfite. This is also same as in 1st version.

So my question - is the 2nd version of EZ-Rodinal correct?