Osmium, colloidal preparation

Iridium Black.204 Iridium(III) hydroxide is reduced in water at 90°C and 8 MPa H2 for 40 min, in the same way as in the preparation of osmium black. The iridium(III) hydroxide is prepared by adding an aqueous lithium hydroxide solution dropwise to an 1% aqueous solution of water-soluble iridium(III) chloride, IrCl3 3H20, at 90-95°C until the pH of the solution becomes 7.5-7.8 under stirring. By keeping the solution at the same temperature under stirring, the precipitate of iridium(III) hydroxide is separated out from its colloidal solution. The precipitate is collected, washed repeatedly with hot water, and then dried in vacuo. 

A characteristic property of the platinum metals consists in tin1 readiness with which they admit of being prepared in the colloidal stale as hydrosols. These latter possess powerful catalytic properties, and their accelerating influence upon the rate of decomposition of aqueous solutions of hydrogen peroxide has been carefully studied. The most, powerful catalyscr is colloidal osmium, followed in order of decreasing activity by platinum, palladium, and iridium.1... 

Osmium Hydrosol or Colloidal Osmium is readily prepared by reducing potassium osmate, K20s04, with hydrazine hydrate in the presence of some protective colloid such as gum acacia 2 or lysalbate (or protalbate) of sodium.3 The reduction may be effected with acrolein 4 if desired. 

Colloidal osmium may also be obtained by reduction of colloidal osmium dioxide. The last named is prepared (see p. 220) by reduction with hydrazine hydrate of potassium osmate solution suspended in lanolin, which serves as protective colloid. The product is dissolved in petroleum, precipitated with alcohol and reduced in a current of hydrogen at 50° to 60° C. A solution containing 21 per cent, of osmium has been obtained in this manner.5... 

A more permanent colloidal solution is obtained in the presence of a protective colloid. It may be prepared, for example,1 by impregnation of lanolin with a solution of potassium osmate. and subsequent reduction with hydrazine hydrate. The lanolin serves as the protective colloid. The product is dissolved in light petroleum and may be precipitated by addition of alcohol. By heating the precipitate to 50° C. in hydrogen, reduction to colloidal metallic osmium takes place. 

Occurronco and History of Osmium -Preparation -Properties Colloidal Osmium—Catalytic Activity—Atomic Weight—Uses Alloys. 

Colloidal dispersions of copper, palladium, silver, osmium, indium, platinum and gold can be prepared using both PVA and PVPD (Tkble 8). 

Wohler obtained phosphorus by strongly heating a mixture of sand and bone-black (calcium phosphate and carbon) — the modern process, now carried out in the electric furnace. He prepared artificial nickel arsenide and worked on the separation of iridium and osmium in a pound of platinum residues given him by Dumas on a visit to Paris in 1833. A supposed silver suboxide, Ag40, prepared by Wohler by the action of caustic potash solution on a supposed subcitrate made by heating silver citrate in hydrogen at 100°, was not analysed and was probably a mixture of silver and silver oxide AggO the red colour of the solution of the subcitrate was probably due to colloidal silver. ... 

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