Chevreul's Salt
Chevreul's salt (copper(I,II) sulfite dihydrate, Cu2SO3•CuSO3•2H2O or Cu3(SO3)2•2H2O), is a copper salt which was prepared for the first time by a French chemist Michel Eugène Chevreul in 1812. Its unusual property is that it contains copper in both of its common oxidation states. It is insoluble in water and stable in air. What was known as Rogojski's salt is a mixture of Chevreul's salt and metallic copper. Preparation Chevreul's salt is prepared by treating aqueous copper sulfate with a solution of potassium metabisulfite. The solution changes colour from blue to green immediately. The identity of the green species is unknown. Heating this solution produces a reddish solid precipitate: 3 CuSO4 + 4 K2S2O5 + 3 H2O → Cu3(SO3)2•2H2O + 4 K2SO4 + 4 SO2 + H2SO4 When sodium ions are present in the solutions that form the salt, sodium can substitute for some of the copper (I), as the ions have the same charge and similar sizes. Reactions Chevreul's salt exhibits properties ...
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