Ammonium thiosulphate is the ammonium salt of thiosulphuric acid.

Chemical formula (NH4)2S2O3
Appearance clear, colourless, aqueous solution
 

Due to the high reaction rate of baths containing ammonium thiosulphate there are several applications in the field of fixing processes into the photographic chemicals sector:
• for quickly various X-ray film materials fixing as well using manual methods as using X-ray film developing machines with short fixing times
• for black and white materials fixing connected with short treatment times, preferably used for processing reproduction materials in developing machines
• for colour materials fixing by using either tank or developing machines
• as well in the fruit growing sector for specific thinning of blossoms
• several urea fertilisers are enriched with ammonium thiosulphate to achieve a selective supply of dissolved sulphur to plant