Potassium vanadium alum

Values for the formation constants of [V(C204)]+ and [V(C204)2] were respectively 1.6 x 107 and 3.5 x 1012.271 By irradiation of these solutions at 254 nm, there is a photodecomposition of the oxalate sensitized by the oxalato vanadium(III) complex the resulting products were equimolar amounts of CO and C02. K3[V(C204)3]-3H20 can be easily crystallized from aqueous solutions containing ammonium vanadium alum and potassium oxalate. The measured magnetic moment is 2.78 BM and this compound obeys the Curie law quite closely.272 The thermal decomposition has been studied.273... 

Alum, KAl(S0i)i-l2H20.—Ammonium, rubidium, cesium, univalent thallium, and in some cases sodium may replace potassium, while the aluminum may be replaced by trivalent iron, chromium, indium, gallium, titanium, vanadium but not by the rare-earth metals. 

Piccini was obsessed with studying the limiting form of the elements as placed in the periodic table. With this in mind, he took up a new field of research, the synthesis of double sulfates (or alums), a work that enormously stimulated his creativity and enthusiasm [58]. In rapid succession, he prepared the alums of vanadium [59], titanium [60, 61], rhodium [62], manganese [63], iridium, and, finally, of thallium [64] with ammonium and then with the following alkaline metals cesium, mbidium, and potassium. Piccini ably used his method of synthesizing the rhodium sulfates virtually to quantitatively separate rhodium from iridium in solution. Through successive fractional crystallizations, Piccini obtained the alums of rhodium and cesium free of iridium, and through electrolysis of the alums he was able to obtain pure rhodium. 

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