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?
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...