Rapid fixers - chloride X sulphate

[Jorge Oliveira]

Hello,

Thre are rapid fixers made by mixing hypo with ammonium chloride or sulphate (Kodak's F-7 and F-9).

It just happens that Kodak F-7 uses 50g of chloride, F-9 uses 60g of sulphate.

The molecular weight of chloride is 53.49g and of sulphate is 132,14g.

Doesn't it looks like there is too little sulphate in F-9?

Thanks,

Jorge

 

[Ole]

Not really. There's roughly twice as much ammonium in the F-7, but the only thing it does is assist in mobilizing the silver ions. It's almost a catalyst. so it doesn't matter (much) how much there is, as long as it's sufficient.
I have no idea how much is sufficient.
My own recipe uses chloride, since I have an idea that the chloride will help in dissolving silver iodide. But I could be completely wrong. At least it works...

 

[Jorge Oliveira]

Thanks, Ole

Jorge O