Quote Originally Posted by Kirk Keyes View Post
Pat - Hardy and Perrin aside, a pinch of sulfite, added before the metol is added to the solution, will consume the small amount of oxygen dissolved in the water. (Cool water will have only about 8-10 mg/L of dissolved oxygen.) Since there is very little oxygen left in the water after the sulfite dissolves, there will be nothing there to oxidize the metol.

So which approach is better?
The oxidation to be concerned about here is that which may have been present at the start. It is not the oxidation that might occur in solution. Granted, it might be quite small in today's product, but who knows? It is the fact (not mine, but what I read in The Theory of the Photographic Process) that whatever amount of Metol may already have oxidized before starting the preparation may be fixed as the sulfonate that I have assumed was the reason for the recommendation by Hardy & Perrin for that deviation from the usual practice of a pinch of sulfite added with the Metol. It's not really much of an inconvenience. It may be that the Q will later revive even the sulfonate. I'm just guessing that it does not . I measured the pH of the solution of Metol in water to be about 5. I will measure it again with the pinch of sulfite. I just thought it a curiosity that Hardy & Perrin used that order of mixing without explaining why, as if everyone else already should know.