Ammonium thiosulfate


Ammonium thiosulfate is an inorganic compound with the formula 2S2O3. It is white crystalline solid with ammonia odor, readily soluble in water, slightly soluble in acetone and insoluble in ethanol and diethyl ether.

Production

It is produced by treating ammonium sulfite with sulfur:

Applications

Ammonium thiosulfate is used in photographic fixer. It is a so-called rapid fixer, acting more quickly than sodium thiosulfate fixers. Fixation involves these chemical reactions :
Ammonium thiosulfate is also used for leaching of gold and silver. It works with presence of copper as a catalyst here. This process is a nontoxic alternative gold cyanidation. The advantage to ammonium thiosulfate is that the pyrolysis of its silver complexes leaves a residue solely of silver sulfide, in contrast to complexes derived from sodium thiosulfate.

Other

Ammonium thiosulfate can be used as a fertilizer. As suggested by some research studies, it can be used as an additive to coal-waste mixtures to reduce formation of very dangerous dioxins and furans.

Safety

is 2890 mg/kg.