It is a moderate reducing agent. It is a source of thiosulfate ion (S2O3-2) (dissolves silver salts). Its major use is as a fixing agent in photography for developing film and the extracting silver from ore. It is used in chrome-tanning leather and in chemical manufacture as a source of sulfide ion. It is also used in paper, textile, and gas purification. Sodium Thiosulfate Anhydrous FCC Wcode:19-051-002 Sales Specifications Sodium Thiosulphate (by mass) : 98.00% Min pH of 10% Solution :6.5 to 9.5 Insoluble in water :0.001% Max Sodium Sulphide :0.001% Max Iron (Fe) : 0.005% Max Loss on drying:1.5% Max Bulk Density :1.667 g/cc Packing 50 lb bag, 44 bags per pallet