The double salt potassio-chromic oxalate presents the curious anomaly of
being pure deep blue when in crystal, claret-red in strong solution, and
dusky green if further diluted. The crystals appear black by reflected,
but blue by transmitted light. A solution made by dissolving ten grains
of potassium bichromate, twenty grains of oxalic acid, and twenty grains
of potassium binoxalate in four ounces of hot water, if put into a white
glass bottle, appears to be a red solution when seen in the direction of
the longer diameter, but a green liquid viewed through the shorter.
[Illustration]