As said, if you are using separate bleach then you can use hypo or better, Ammonium thiosuphate.
If you are in Europe try fotosuvatlar@live.de who delivers it promptly at a good price. It is much faster at clearing than plain hypo.
It is not recommended to use b&w fixer for C-41 films, due to a pH issue. On the other hand, C-41 fixer can be used for b&w films and paper. I use C-41 fixer for everything as it is inexpensive, but apparently, hard for you to find.
Don't use Sodium Hypo. It is not strong enough to fix C41 films unless you are willing to wait for a loooong time! Say 20+ minutes at 100F for example.
Use straight Ammonium Hypo solution (it comes in a standard concentration) diluted 200 ml /L of water with a pinch of Sodium Sulfite and some Acetic acid added until the ammonia disappears. This is the easy way, even if the pH might not be exact.
Don't use Sodium Hypo. It is not strong enough to fix C41 films unless you are willing to wait for a loooong time! Say 20+ minutes at 100F for example.
Use straight Ammonium Hypo solution (it comes in a standard concentration) diluted 200 ml /L of water with a pinch of Sodium Sulfite and some Acetic acid added until the ammonia disappears. This is the easy way, even if the pH might not be exact.
I make and use ECN-II fix for ECN and C41. It is pretty much as you say. 200mL 60% NH4S2O3, 10g Sodium Sulfite and 8.4g Sodium Metabisulfite. Fill with demin. Water to 1L. No need to adjust the pH. It should be around 6.5. I'll check with my brand new pH Meter next time I mix some up, but the lovely smell of ammonia is definitely gone. Requires to source both salts, though.
I follow your advice, now, and fix C41 a bit longer with that fix. But I have some chemicals on order and want to try your superfix. Would the sulfite/metabisulfite buffer work with it, or should I use sulfite/acetic acid as per your recipe?
Don't use Sodium Hypo. It is not strong enough to fix C41 films unless you are willing to wait for a loooong time! Say 20+ minutes at 100F for example...
There are two factors which limit the usefulness of Sodium Thiosulfate:
poor diffusion of sodium ion through gelatin, which slows diffusion of thiosulfate
formation of mixed salts of sodium, silver, thiosulfate and halide, in particular iodide
The first aspect will affect observed fixing speed and can be solved with addition of ammonium salts, whereas the second aspect will limit fixer capacity and won't be overcome with addition of ammonium salts. Since C-41 film uses 3-12 silver halide layer and typically high in iodide, fixer capacity is an important factor.