But Metol and hydroquinone are not superadditive without sulfite. That also is shown in the graph in Mees and James.

The ratio of ascorbic acid to Phenidone in PC-TEA is about 40 to 1 by weight. I don't know the molecular weight of Phenidone but that of ascorbic acid is 176. That was the ratio at which the increase in activity levelled off as ascorbic acid was added to 0.05 moles/liter of phenidone. I dont remember where I got the molecular weight of Phenidone for that experiment, nor what value I used. I am looking at the graph. I will look up the text. I'm sure you know the MW.