Making some Parodinal, but would appreciate more insight...

[Gerald C Koch]

Glycin and metol are also related molecules, and I suspect they may also be transformed into Rodinal.

Add to this list hydroquinone. Phenols easily form phenolates with strong alkalies like sodium hydroxide. During WW! it was impossible to obtain Rodinal. An American photographer created a delevoper concentrate which acted like Rodinal. It contained metol and hydroquinone and was sold as Kalogen. You can find his formula and advertisement on the Library of Congress website. I have used a modified version of this developer for film and prints for over 10 years. Like Rodinal it lasts for years.

 

[chiller]

I tried to locate pure paracetamol but had no luck so my version is based on 30 crushed 500mg tablets. I have a very nice granite mortar and pestle and ground the tablets to an extremely fine state.
My developer is not clear like your version, milky in fact, but there is no detrimental action on the negative because of the tablet filler.
A hard compact layer of I presume filler is forming on the bottom of the bottle. This layer is about 1 mm and may have some crystals as well. Due to the cloudiness of the developer I cannot really tell for certain.
I use a 10 ml glass pipette to measure my developer so eventually when I get too close to this filler layer I will dump what is left and make a new batch.
Based on my initial results I'm not concerned about using the tablets and won't stress about the cloudiness of the developer.
I have a batch curing at present that I made 2 days ago with Sodium Metabisulphite and KOH. I will test a sheet today or tomorrow and report back. If it is successful I will post the quantities I used.

Thanks again to Jaco for helping with the quantities needed. I'm not a chemist. A careful tinkerer but definitely not a chemist.

 

[Gerald C Koch]

A hard compact layer of I presume filler is forming on the bottom of the bottle.

The technical word you want is excipient. Since they are usually insoluble in water you don't have to grind the tablets very much. If you just break the tablets up a bit you will probably avoid the cloudiness problem.

 

[Gerald C Koch]

Don't filter, just put in everything and let it simmer.

Paraminophenol is very sensitive to oxidation and so it is best not to use heat. Be patient and the hydroxide will split off the acetyl group.

You can prepare paraminophenol by refluxing the tablets with dilute hydrochlioric acid. You will need a suitably sized Erlenmeyer flask, a one-hole rubber stopper and a two foot length of glass tubing. Use 1N hydrochloric acid and heat for about an hour. The tubing acts as a primitive condenser. The mixture does not have to boil. Since some hydrochloric and acetic acids will be released this is best done in the open air. Allow the mixture to cool and then filter it. The free base paraminophenol can be precipitated with either sodium carbonate or bicarbonate. Do the neutralization gradually to prevent foaming. To prevent oxidation add a pinch of sodium sulfite to the solution before adding the carbonate. The free base will form as buff colored greasy scales. It can be recrystallized by dissolving in hot water to which a small amount of sodium sulfite is added and allowing the solution to cool.