Rhodium sulfate

Rhodium complexes with oxygen ligands, not nearly as numerous as those with amine and phosphine complexes, do, however, exist. A variety of compounds are known, iucluding [Rh(ox)3] [18307-26-1], [Rh(acac)3] [14284-92-5], the hexaaqua ion [Rh(OH2)3] [16920-31 -3], and Schiff base complexes. Soluble rhodium sulfate, Rh2(804 )3-a H2 0, exists iu a yellow form [15274-75-6], which probably coutaius [Rh(H20)3], and a red form [15274-78-9], which contains coordinated sulfate (125). The stmcture of the soluble nitrate [Rh(N03)3 2H20 [10139-58-9] is also complex (126). Another... 

Principal Compounds Rhodium trichloride rhodium trioxide rhodium (II) acetate rhodium nitrate rhodium potassium sulfate rhodium sulfate rhodium sulfite... 

Aqueous chemistry. This chemistry is almost exclusively that of complex compounds. Aquo ions of Ru11, Rum, Rh111 and Pd11 exist, but complex ions are formed in presence of anions other than CIO4, BFJ, or -toluene-sulfonate, etc. The precise nature of many supposedly simple solutions, e.g., of rhodium sulfate, is complicated and often unknown. 

M.p. 1970 °C. Harder and more difficult to work than Pt. The solid metal and the fine rhodium black powder obtained by reduction from salt solutions differ in their solubility in acids. The solid metal is insoluble in all acids and mixtures of acids, and is not attacked by molten NaOH even if KNO3 is added at dull red heat. If Rh is fused with KHSO4, it slowly forms the water-soluble potassium rhodium sulfate, which imparts a dark-red color to the melt at high Rh concentrations, the melt becomes black. 

According to Krauss and Umbach, attempts to prepare rhodiiun sulfate from rhodium hydroxide and sulfuric acid lead to two different products, depending on the conditions these are yellow rhodium sulfate Rh3(S04)3 15 HgO and red rhodium sulfate Rhs(S04)3 4 HgO. 

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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