Sodium thiosulfate, also known as sodium metabisulfite, sodium bicarbonate and hypo, is a common thiosulfate with the chemical formula of Na2S2O3, which is the product that an oxygen atom in sodium sulfate is replaced by a sulfur atom, so the oxidation numbers of the two sulfur atoms are -2 and +6 respectively.

Mainly used as fixing agent in photography industry. Secondly, it is used as reducing agent of dichromate, neutralizer of nitrogen-containing tail gas, mordant, bleaching agent of wheat straw and wool, dechlorination agent in pulp bleaching. It is also used to make tetraethyl lead, dye intermediates and extract silver from ores.

Production method:

Alkali sulfide method: the raw material liquid prepared from the evaporation residue of alkali sulfide and barium sulfide wastewater (containing sodium carbonate and sodium sulfide) reacts with sulfur dioxide, and after clarification, sulfur powder is added for heating reaction, and after evaporation, cooling crystallization, washing, separation and screening, the finished product of sodium thiosulfate is obtained.

Comprehensive method: the main components are sodium sulfide, sodium sulfite, sulfur and a small amount of sodium hydroxide. After vacuum evaporation, decolorization by activated carbon, filter pressing, cooling, crystallization, centrifugal dehydration and screening, the finished product is obtained.

Refer to the above content: Baidu Encyclopedia-Sodium thiosulfate