Chromate tris malonato

Potassium tris(malonato)chromate(IIl) trihydrate can be prepared by the method of Lapraik, reacting freshly precipitated chromium(III) hydroxide with malonic acid and potassium carbonate. Lapraik obtained the crystals by drying the aqueous solution over sulfuric acid, but the crystals are more easily obtained by precipitation in ethanol. 

Potassium tris(malonato)chromate(IlI) trihydrate is a blue-green compound which is very soluble in water. The cis isomer of potassium diaquabis(malo-nato)chromate(III) trihydrate is purple and also very soluble in water. The trans isomer is violet and fairly soluble in water, but it is more soluble than the analogous oxalate compound. All three compounds exhibit two absorption maxima in their visible absorption spectra, listed in Table I. 

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