Sodium thiosulfate (Na2S2O3·5H2O), also known as sodium hyposulfite, baking soda, or hypersite, is a common thiosulfate that has a variety of important industrial and medical applications.
Preparation method
1. Sodium sulfite method: This is a common method for preparing sodium thiosulfate. First, the soda ash solution reacts with sulfur dioxide gas to form sodium sulfite, then caustic soda is added for neutralization, and sodium sulfide is added to remove impurities. After a series of steps of filtration, impurity removal, re-filtration, alkali treatment with caustic soda, the finished product of sodium thiosulfate is prepared through the process of concentration, filtration, crystallization, centrifugal dehydration, screening and so on.
2. Vulcanized alkali method: Using alkali sulfide evaporation residue and barium sulfide wastewater to react with sulfur dioxide, adding sulfur powder after clarification for heating reaction, and then through evaporation, cooling crystallization, washing, separation, screening and other steps to produce sodium thiosulfate.
3. Dewatering method: sodium thiosulfate pentahydrate crystallization is heated indirectly by steam to dissolve in its own crystalline water, and anhydrous sodium thiosulfate is obtained through concentration, centrifugal dehydration, drying and screening.
Sodium thiosulfate (Na2S2O3·5H2O) is a multifunctional chemical, which has a wide range of applications in many fields. Here are some of the main application areas of sodium thiosulfate:
1. Photographic industry: sodium thiosulfate is used as a photographic fixer in the photographic industry for fixing images on film and photographic paper.
2. Water treatment: In the water treatment industry, sodium thiosulfate can be used as a dechlorination agent for drinking water and wastewater, a fungicide for removing chlorine from tap water, and a copper corrosion inhibitor for circulating cooling water.
3. Chemical raw materials: As a chemical raw material, sodium thiosulfate is used as a reducing agent of dichromate in the leather industry, as a dechlorinator after pulp bleaching in the paper industry, and as a dechlorinator after cotton fabric bleaching in the printing and dyeing industry.
4. Analytical chemistry: In analytical chemistry, sodium thiosulfate is used as reagent for chromatographic analysis, volume analysis, as well as bleach for wheat stalk and wool and dechlorination agent for pulp bleaching.
5. Medical use: Sodium thiosulfate is mainly used for patients with cyanide poisoning, and can also be used for the treatment of arsenic, mercury, lead, bismuth, iodine and other poisoning. It provides sulfur, which binds to CN-, which is free in the body or has been bound to methemoglobin, to form a less toxic thiocyanate, which is detoxicated with urinary excretion.
6. Environmental protection: Sodium thiosulfate has been widely used in aquaculture industry because of its low price, high efficiency and no pollution in water quality improvement, which has the effect of removing residual chlorine in water, degrading nitrite and so on to improve water quality.
7. Other industrial applications: Sodium thiosulfate is also used in the manufacture of tetraethyl lead, dye intermediates, and ore silver extraction.
Sodium thiosulfate has become one of the most important chemicals in the chemical industry because of its wide application in many fields.