Sodium Rhodate, Na₂RhO₄

If the-gases evolved by the action of hydrochloric acid upon potassium chlorate are passed into a solution of a rhodium salt rendered alkaline with sodium hydroxide, the liquid assumes a yellowish red, then a red colour, and finally a slight green precipitate forms. The latter dissolves, yielding a solution of blue colour known as Clauses Blue, and containing Sodium Rhodate, Na₂RhO₄.

Sodium peroxide destroys the colour, as do also potassium persulphate and sulphur dioxide.