TF-2 Alkaline fixer exact recipe and capacity

in TF-2 recipe states for 250 g sodium thiosulfate in pentahydrate or anhydrous form?

the recipe as is published everywhere:
Sodium Thiosulfate - 250 g
Sodium Sulfite (anhy) - 15 g
Sodium Metaborate - 10 g

it's never stated anywhere so I'm confused about.

also - can anyone estimate TF-2's capacity? I suppose it will be somewhere about 20-25 films / liter but I'm really not sure (I don't know how to compute that scientifically).

thanks (and please excuse my horrible english)

Pentahydrate. Most of the recipies I've seen are 1M solutions of sodium thiosulfate. If the recipe states 250g, then it's the pentahydrated form, because the molecular weight of sodium thiosulfate + 5 molecules of water is very close to 250g. The capacity is probably about 20 films, but only tests can reveal the facts.

If you are using it for film, then there is the 'leader' test, as I call it. Drop a spot of the fixer on the leader (i.e the bit of film that you cut off when you load the film onto the reel. It can be fully exposed to light, and will work just fine) let the drop sit there for a minute or two, so that spot will be fixed first. Then drop the whole leader into a claer container of the fresh fixer. Time how long it takes the rest of the film chip to get as clear as the drop that you started earlier.

Then start using your fixer in everyday use. After, say, 10 films, repeat the leader test. You know the fixer is approaching exhaustion when it takes twice as long to clear as it did when it was fresh.

As far as I know this test using film leaders can be used for film and paper fixers. Some people dilute fixer for paper use. If you are such a person, start your test with fresh paper dilution fixer for the first fresh test for that dilution.

I use some fixers at 'film' strength. even for paper. I don't mix paper fixer and film fixer; I am concerned that paper bits might get stuck to my film after the bath has processed FB papers.

thanks a lot!