Question about Ammonium thiosulfate 60% solution

[LFLarry]

I am in the process of researching how to make TF-3 in the Darkroom Cookbook and it calls for a 60% solution of Ammonium thiosulfate.

I looked on all the obvious photo chemical websites and it appears that it is sold in liquid form at the 60% solution.

I was wanting to make my own 60% solution from dry chemicals so I could mix it and my TF-3 on demand. I don't like to have pre-mixed chemicals sitting around if I can avoid it because I never know when or how much I will need.

Does anyone know how to make the 60% Ammonium thiosulfate from dry chemicals? I searched for Ammonium thiosulfate in dry crystal form, but not having much luck.

I am wondering why all these suppliers are selling it as a pre-mixed 60% solution? There must be a reason that I don't understand, so any help is appreciated.

Thank you!

[koraks]

Ammonium thiosulfate can be found as dry crystals. Not many places sell it, but it can be bought. It's used (among others) as a fertilizer, perhaps that helps. Prices can vary but in general, it may be more expensive than you'd expect, certainly if you use the sodium salt as a reference

[LFLarry]

Thanks, good info. I appreciate it.


Ammonium thiosulfate can be found as dry crystals. Not many places sell it, but it can be bought. It's used (among others) as a fertilizer, perhaps that helps. Prices can vary but in general, it may be more expensive than you'd expect, certainly if you use the sodium salt as a reference

[Ken Lee]

I make my own Fixer on demand 1 liter at a time at working dilution (http://www.kennethleegallery.com/html/tech/index.php#alkaline) from the liquid 60% solution which I purchased from Artcraft Chemicals.

[LFLarry]

Thanks Ken, I appreciate it. Love your website.



I make my own Fixer on demand 1 liter at a time at working dilution (http://www.kennethleegallery.com/html/tech/index.php#alkaline) from the liquid 60% solution which I purchased from Artcraft Chemicals.

[LabRat]

I don't have the formula in front of me, but it's about 175ml per liter of 60% for film, and 150ml for paper, and the rest of the dry ingredients added...

Don't try to male a concentrated stock stronger than you would use for 1:4 or solids will fall out of the solution...

Steve K

[goamules]

We wetplaters use it for fixer all the time. Dry form is how I commonly buy it from Artcraft or Bostick and Sullivan. Don't know how to get to your percentage ratio, I have a formula I use, but don't know it's percentage.

[Joe O'Hara]

The reason why it is sold as a solution rather than a powder (as I understand) is that dry ammonium
thiosulfate is highly hygroscopic, i.e., it absorbs significant water from the atmosphere. (It may even be
deliquescent, i.e., absorbing enough water to actually liquefy upon standing. Chemists here can check
me on that.) Accordingly, dry ammonium thiosulfate is never really dry (if unsealed) and thus cannot be
depended upon to be weighed correctly, due to the unknown portion of water present.

It's a nuisance that we have to pay to ship the water along with the chemical that we want, but
for me the much faster fixing action is worth it.

[LabRat]

Oh, and dilute slightly until it clears a piece of scrap film for 1 - 2 minutes, then double that time in use...

Steve K