Strontium Dithionate, SrS₂O₆

Strontium Dithionate, SrS₂O₆, is formed by neutralising dithionic acid with strontium hydroxide. It is isomorphous with the corresponding calcium salt. It may also be obtained by acting upon strontium nitrate with sodium dithionate in solution, cooling slowly, and evaporating the solution at or above 50° C., when a monohydrate is obtained. At ordinary temperatures it crystallises with 4 molecules of water in large hexagonal plates, which are stable in air and rotate the plane of polarisation to the left. The solution is inactive. The salt loses water of crystallisation at 78° C. It dissolves in 4.5 parts of water at 16° C. and in 2.5 parts at 100° C., but is not very soluble in alcohol. The heat of solution in water is –9.250 Cal.