Properties: colorless transparent monoclinic crystal, odorless, taste salty, specific gravity 1.729, heated to 100 ℃, loss of five crystal water. Soluble in water, insoluble in alcohol, in acidic solution decomposition, has a strong reductive. At 33 ℃ or more easily in dry air weathering in the moist air, there deliquescence.
Uses: Used the industry as a photographic fixing agent. Used in electroplating, purify water and tanning leather, was also used for chemical industry, reducing agent, bleaching cotton after the dechlorination agent, sulfur dyeing wool fabric dye, indigo dye anti-white agents, pulp dechlorination agent, the pharmaceutical industry used as detergents, disinfectants and bleaching agents.