Potassium Tris malonato chromate III Trihydrate

Inorganic Syntheses, Volume XVI Edited by Fred Basolo Copyright 1976 by McGraw-Hill, Inc. 

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. 

A solution of 30 ml of concentrated (15M) ammonium hydroxide in 170 mi of H2O is added, with stirring, to a solution of commercial chromium(III) chloride hexahydrate (13.3 g, 0.05 mole) in 200 ml of water. The precipitated chromium(III) hydroxide is centrifuged.  

POTASSIUM cis- AND tran DIAQUABIS(MALONATO CHROMATE(III) TRIHYDRATE 

A solution of potassium dichromate (11.8 g, 0.04 mole) in boiling water (25 ml) and a solution of malonic acid (20.8 g, 0.20 mole) also in boiling water (25 ml) are mixed and allowed to react until no more carbon dioxide evolves. Then water is added to the mixture to make a volume of ca. 200 ml. 

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