Reading Haist: what is more powerful, hydroquinone or catechol?

[Pixophrenic]

Original idea, Murray, I wonder why the old timers never produced such a formula AFAIK. Presumably HQ would regenerate PPD as maybe does ascorbate in Jay DeFehr's Halcyon developer:
https://www.largeformatphotography....?71010-Halcyon-superfine-grain-film-developer.
This is different to the other old PPD developers where PPD was partly a developer but mainly a solvent and and another developer, metol, glycin etc was added to speed up the process at the expense of grain, not to regenerate PPD.

In my limited experience, a combination of equimolar PPD with hydroquinone precipitates out of solution at moderate pH (8-9). If more alkali is added, the precipitate dissolves but the resultant developer is rather active and too contrasty. Perhaps this answers a related question why PPD:hydroquinone adduct called "hydramine" never got popular as a "new" developing agent. In contrast, a combination of CD-2 and hydroquinone is used in a current developer Atomal 49 from Adox, which I tested and liked.

 

[Pixophrenic]

I don’t have any yet. It just thoughts. It would sometimes be helpful to have a less active hydroquinone alternative.

Well, hydroquinone monosulfonate is exactly this. If you are not alien to experiments with oxidizing hydroquinone and then reacting it with sulfite, you may arrive at something useful. I am not publishing my experiments because I am not sure they are reproducible elsewhere in the world. I mean, my hydroquinone it "too pure" ;-)