From Darkroom Pro's site:

Kodak's F-7 Rapid Fixer

Sod. Thiosulfate 360g
Amm. Chloride 50g
Sod.Sulfite 15g
Acetic Acid (28%) 48ml
Boric Acid 7.5g
Pot. Alum 15g
Water to make 1.0L

This is a standard rapid fix with all the hardening mixed in. Fixing times are 5 min. at 70 F for T-Max films.

If you don't want hardening, look for Kodak F-8

I use a similar formula - but with ammonium sulphate (that's whai I found at the chemist).

Jorge O