Alums rhodium

Rhodium and the Halogens —Hcxa-ohlor-rhoditos—Ponla-clilor-rhodilcs - -Rhodium and Oxygen—Rhodium and Sulphur—Tho Alums—Rhodium and Nitrogen—Rhodium, Phosphorus, and Arscaio—Rhodium and Carbon -Rhodi-oyanides. 

Despite the above similarities, many differences between the members of this triad are also to be noted. Reduction of a trivalent compound, which yields a divalent compound in the case of cobalt, rarely does so for the heavier elements where the metal, univalent compounds, or hydrido complexes are the more usual products. Rhodium forms the quite stable, yellow [Rh(H20)6] " ion when hydrous Rh203 is dissolved in mineral acid, and it occurs in the solid state in salts such as the perchlorate, sulfate and alums. [Ir(H20)6] + is less readily obtained but has been shown to occur in solutions of in cone HCIO4. 

An interesting scries of salts is afforded by the alums of trivalent iron, cobalt, rhodium, and iridium. These have the general formula... 

Cobalt, rhodium, and iridium yield sulphates of the type R2(S04)a, and these combine with sulphates of the alkali metals to produce alums, of the general formula MaS01.R2(S01)3.24H80. These are well-defined... 

Cobaltic sulphate, like the sulphates of rhodium and iridium, unites with the sulphates of the alkali metals to yield a series of well-defined, crystalline salts known as alums. These are isomorphous with those of iron, manganese, chromium, and aluminium, and form an interesting link between these metals and the central vertical column in Group VIII of the Periodic Table, of which column cobalt is the first member. 

Rhodium, like cobalt, iron, and aluminium, yields a well-defined series of alums. Application of Mitscherlich s Law of Isomorphism indicates that these have the general formula ... 

Sodium Rhodium Sulphate, NasS04.Rh2(S04)3, was first prepared by Bunsen3 by heating sodium rhodium sulphite with concentrated sulphuric acid. Tliis salt was regarded by Seubert and Kobbe 4 as an anhydrous rhodium alum. Since then, however, true rhodium alums have been obtained. 

Caesium Rhodium Alum, Cs2S04. Rh2(S04)3.24H20, is the most readily prepared of all the rhodium alums on account of its sparing solubility in cold water. The salt crystallises in small yellow octahedra which melt at 110° to 111° C. to a yellowish red liquid. When warmed in a desiccator it loses water, remaining yellow at 100° C., becoming yellowish red at 150° to 180° C., and brown up to 250° C., when it is almost entirely anhydrous. 

This alum is of interest inasmuch as its formation renders it easy to separate rhodium from iridium. The sulphates of the metals, dissolved in acidulated water, are treated with caesium sulphate and evaporated. The rhodium alum crystallises out in a pure state, entirely free from iridium.1... 

Rubidium Rhodium Alum, Rb2S04.RhL(S04)3.24H20, yields stable yellow crystals which melt at 108° to 109° C. to a bright red liquid.1 The crystals belong to the regular system and exhibit a eonchoidal fracture. 

Potassium Rhodium Alum, K2S04.Rh2(S04)3.24H20, can only be obtained in a crystalline state by allowing the solution to stand for a prolonged period at a temperature not exceeding 5° C. At higher temperatures a syrupy, uncrystallisable liquid results.1... 

Thallium Rhodium Alum, Tl2S04.Rh3(S04)3.24H20, is somewhat difficult to prepare, partly on account of the small solubility of thallous sulphate. The alum is very soluble in water, and not altogether permanent in air, becoming converted into a whitish powder on prolonged exposure.1... 

The sulphates of rhodium and iridium form yellow alums with the sulphates of K, NH4, Rb, Cs and TF. The salts themselves are formulated Rh2(S04)g.l5H20 and 2(804)3121120. Like palladium(II) sulphate, PdS04.2H20, they are made by the action of H2SO4 on the metals. 

In its trivalent form, iridium forms the sesquisulfate, Ir2(S04)j, which like the corresponding salts of cobalt and rhodium forms a series of alums. 

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. 

DEKTAL DEVELOPER KODAK FIXER KODAK SHORT STOP POTASSIUM ALUM POTASSIUM BICARBONATE POTASSIUM BICHROMATE POTASSIUM BORATE POTASSIUM BROMATE POTASSIUM BROMIDE POTASSIUM CARBONATE POTASSIUM CHROMATE POTASSIUM CHLORATE POTASSIUM CHLORIDE POTASSIUM CYANIDE POTASSIUM DICHROMATE POTASSIUM FERRICYANIDE POTASSIUM FERROCYANIDE POTASSIUM FLUORIDE POTASSIUM HYDROXIDE POTASSIUM NITRATE POTASSIUM PERBORATE POTASSIUM PERCHLORATE POTASSIUM PERMANGANATE. 10% POTASSIUM SULFATE PROPANE PROPANE GAS PLATING SOLUTIONS BRASS CADMIUM COPPER GOLD INDIUM LEAD NICKEL RHODIUM SILVER TIN ZINC... 

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