Sodium ThioSulfate Na2S2O3*5H2O 99.5% 2 lb
Mainly used to dechlorinate tap water for aquariums or treat effluent from waste water treatments prior to release into rivers. The reduction reaction is analogous to the iodine reduction reaction. Treatment of tap water requires between 0.1 grams and 0.3 grams of pentahydrated (crystalline) sodium thiosulfate per 10 liters of water.It is also the old time Hypo used in photography.