Quote Originally Posted by Photo Engineer View Post
Ian, Patrick;

According to my texts, the Sodium Bisulfite available commercially is mostly Sodium Metabisulfite. The same texts do not claim that for the Potassium salt. So, apparently, the Sodium salts are in equillibrium in the solid and liquid state.

PE
In a few previous post I listed the variation of that equilibrium in Commercial Sodium Bisulphite (Kodak and JT Baker - very similar), and the purer Sodium Metabisulphite plus a reference to a Kodak paper on substitution ratio of one for the other.

Potassium Metabisulphite is sold in Home Brew shops and Boots The Chemist (UK) used to stock it. in 250gm Bottles.


Now back to Rodinal


What I was trying to suggest or rather asking is the effects of "the one SO2 and one mole of SO3 upon decomposition in water, both of which end up making HSO3- or the equivalent. It is acidic in water."

I'm referring to the "Orginal formula" Andresen suggests, and many book from Agfa in the early 1900's right through to the recent Darkroom Cookbook.

Yes it's definitely acid until the formulae is balanced with Hydroxide, my point is something different is happening when Metabisulpite's used because of the SO2 & SO3 which won't happen if we used the equivalent amount of Sulphite.

In most developers using small amounts of Metabisulphite it's probably irrelevant but in this old developer with such a high level it has to make a difference.

Ian