Quote Originally Posted by Photo Engineer View Post
Kodak found that early PPD developers were affected by the acid used to make the salt, and converted to either the Sulfate or the p-Tosyl salt which you see in use today. This is true to the present time in CD-6 and CD-3 for example. The chloride had varying adverse effects on early Cl/Br emulsions used in print films and papers. I don't know what all was affected, as the change was complete when I joined EK.
PE

Kodak also did a lot of work on p-Aminophenol and it's derivatives in the 30's & 40's, there are various Patents etc, Sheppard was involved and must have moved from Wratten to Rochester with Mees.

Your comments about the PPD acid salts are matched by Kodak's use of p-Aminophenol Oxalate, and Edmund Lowe's Gradol the sulphate form and confirm what I'm thinking about the importance of the free base in Rodinal.

On the point of ascorbic, here's the second to last paragraph from Edmund Lowe's 1939 book on Developers:

As for developers, it is probable that the next few years will see the introduction of a series of developing agents that that can actually be eaten if desired. Some, chemically related to Vitamin C, are available now though at enormous cost. One call almost see the advertisement of the new Zero-Grane 999 (1960 A.D.) ----- "Try Zero-Grane 999. Non-poisonous. Enlargement to 999 diameters, miraculously discovered by George Gizzlewski after 84 years of painstaking research. If it won't develop your negative, take two teaspoonsful after each meal. It puts spring in your step and a light in your eye. $10 per 2 oz. bottle sufficient for 89 rolls of film."

It's Lowe's nice way of saying there's no magic bullets.

Ian