Frustrating Issues with HC-110

[bnxvs]

Please explain why you decided that methol or p-aminophenol are less susceptible to oxidative processes in aqueous solution (with or without sulfite ion) than phenidone and its derivatives?
p.s. By the way, I know what is part of the Rodinal ))) It was just an analogy ... It seemed to me that this would be understandable to any photochemist. Apparently it seemed ... ((

 

[Donald Qualls]

I'm not a photochemist, nor any kind of chemist; my last formal chemistry education was an inorganic chemistry class as a college freshman around 1978 (though I've learned a lot of theory-deficient results-based information about photochemistry in the past twenty years). I do know that developers based on phenidone and its derivatives (like the dimezones) have a long standing reputation for poor shelf life of stock solution compared to comparable (-seeming) metol-based products. The only common p-aminophenol based developers are all direct derivatives of Rodinal, the version of which that was popular in the last half of the 20th century has a very longstanding reputation for exceptional concentrate shelf life, even in partly filled bottles without any effort to exclude air short of simply closing the lid.

 

[Alan Johnson]

Please explain why you decided that methol or p-aminophenol are less susceptible to oxidative processes in aqueous solution (with or without sulfite ion) than phenidone and its derivatives?

The silver bromide is generally reduced by the unstable developer semiquinones so it might be worthwhile to look at the half life of each of these as the reaction with oxygen may be similar.

 

[bnxvs]

I think there was some confusion in the discussion. We should not confuse the situations of oxidation of the developing agents in the presence of sulfite ions and without sulfite. I emphasize once again - almost all common developing agents are actively oxidized by oxygen dissolved in water in the absence of sulfite. It is a fact. The kinetics of these processes has been studied in detail for a long time. And from a practical point of view, the rate of oxidation of metol, p-aminophenol or phenidone is not much different. As for solutions containing a significant proportion of sulfite in relation to the amount of water, it can be unambiguously asserted that oxidative processes will take a very long time, again for any common developing agent or their combinations.
Accordingly, I do not understand very well what exactly you want to prove with your theses - that Rodinal is better than HC-110? It isn't a fact. That p-aminophenol is oxidized later in a supersaturated sulfite solution than phenidone? Also not a fact. Personally, I don't have an extra couple of years to conduct such experiments, especially since it will not give anything in a practical sense, at all.