Chromium amalgams

Chromium (II) also forms sulfides and oxides. Chromium (II) oxide [12018-00-7], CrO, has two forms a black pyrophoric powder produced from the action of nitric acid on chromium amalgam, and a hexagonal brown-red crystal made from reduction of Cr202 by hydrogen ia molten sodium fluoride (32). Chromium (II) sulfide [12018-06-3], CrS, can be prepared upon heating equimolar quantities of pure Cr metal and pure S ia a small, evacuated, sealed quartz tube at 1000°C for at least 24 hours. The reaction is not quantitative (33). The sulfide has a coordination number of six and displays a distorted octahedral geometry (34). 

The black powder ignites if ground or heated in air [1], The oxide obtained by oxidation of chromium amalgam is pyrophoric [2],... 

Chromous Oxide, CrO, is obtained by the oxidation in air of chromium amalgam or, preferably, by the action of dilute nitric acid upon chromium amalgam. It is a black powder which inflames when struck with a pestle, or when heated in the air, but not in a vacuum, and bums, forming the sesquioxide. It is insoluble in nitric acid and in dilute sulphuric add, but in hydrochloric acid it dissolves, forming a blue solution and liberating hychogen in accordance with the equation ... 

Black chromium(II) oxide, CrO, is most conveniently made (Dieckmann and Hauf, 1914) by dissolving the mercury out of chromium amalgam with... 

X 10 ii per cent. C. F. Schonbein, N. Bunge, Z. Roussin, and C. W. Vincent prepared a mercury-chromium alloy or chromium amalgam, by the action of potassium or sodium amalgam on a cone. soln. of chromic chloride and H. Moissan obtained the amalgam by a similar process, as well as by the action of sodium amalgam on chromous chloride, bromide, or iodide. R. Myers obtained it by the electrolysis of a soln. of chromic sulphate in dil. sulphuric acid using a platinum anode, and mercury cathode J. Feree found that with a soln. of chromic chloride the yield is poor. 

Titanium Sulfates. Solutions of titanous sulfate [10343-61-0] ate readily made by reduction of titanium(IV) sulfate ia sulfuric acid solutioa by electrolytic or chemical means, eg, by reduction with ziac, ziac amalgam, or chromium (IT) chloride. The reaction is the basis of the most used titrimetric procedure for the determination of titanium. Titanous sulfate solutions are violet and, unless protected, can slowly oxidize ia coatact with the atmosphere. If all the titanium has been reduced to the trivalent form and the solution is then evaporated, crystals of an acid sulfate 3 Ti2(S0 2 [10343-61-0] ate produced. This purple salt, stable ia air at aormal temperatures, dissolves ia water to give a stable violet solutioa. Whea heated ia air, it decomposes to Ti02, water, sulfuric acid, and sulfur dioxide. 

Ghromium(II) Compounds. The Cr(II) salts of nonoxidizing mineral acids are prepared by the dissolution of pure electrolytic chromium metal ia a deoxygenated solution of the acid. It is also possible to prepare the simple hydrated salts by reduction of oxygen-free, aqueous Cr(III) solutions using Zn or Zn amalgam, or electrolyticaHy (2,7,12). These methods yield a solution of the blue Cr(H2 0)g cation. The isolated salts are hydrates that are isomorphous with and compounds. Examples are chromous sulfate heptahydrate [7789-05-17, CrSO 7H20, chromous chloride hexahydrate... 

Reductant equivalent weights of, 847 Reduction 409 by chromium(II) salts, 409 by hydrogen sulphide, 416 by Jones reductor (zinc amalgam), 410 by liquid amalgams, 412 by silver reductor, 414 by sulphurous acid, 416 by tin(II) chloride, 415 by titanium(II[), 410 by vanadium(II), 410 see also Iron(III), reduction of Reduction potentials 66 Reference electrodes potentials, (T) 554 Relative atomic masses (T) 819 Relative error 134 mean deviation, 134... 

Compact chromium is not dangerous. The meteil powder ( pyrophoric ) obtained by the amalgam evaporation is the only one that represents risk. As far as chromium... 

Evaporation of mercury from mercury amalgam leaves pyrophoric chromium [1]. Increasing the temperature at which hexacarbonylchromium is thermally decomposed increases the surface area and pyrophoricity of the chromium powder produced [2],... 

A( ueous solutions of chromium(ll) sulfate have Ijeen prepared from chromium(lll) sulfate by reduction with zinc powder and from potassium dichromate by reduction with amalgamated zinc and sulfuric acid. Solid chromitim(II) sulfate penlahyrlrate can be obtained from the reaction of highly purified chromium metal... 

Sodium forms alloys with a number of metals including lead, chromium, mercury, aluminum, silicon, and iron. With mercury, it forms sodium amalgam. Sodium-lead alloy is commercially used to produce tetraethyllead, which was used historically as an additive to gasoline ... 

The reduction of aqueous chromium(III) solutions can be carried out electrolytically o chemically with zinc amalgam, zinc and acid or a Jones reductor.2,24 Electrolytic procedures ca be cumbersome, and with chemical reductants contamination with other products can occur Chromium metal and acid can be used to reduce chromium(III) salts, and this requires less c the metal than in the method described in Section 35.3.1.1.i. 

In earlier studies mercury has been plated onto electrodes to be used in voltammetric and spectrochemical analysis.2 DeAngelis (1976) developed thin film mercury electrodes by plating a solution of mercuric nitrate onto a variety of different electrodes in order to detect the presence of trace metals in small volumes. The results demonstrated that mercury plating occurred with tungsten, vanadium, chromium, and iron and there was little amalgamation. 

For the latter reaction very pure chromium is required to prevent formation of Cr34, but the reaction with a zinc amalgam is clean and is a convenient source of the strongly reducing species. Addition ofCr2 solutions to saturated solutions of sodium acetate precipitates chromium(U) acetate ... 

HOMOALLYLIC ALCOHOLS Cerium amalgam. Chromium(II) chloride. Fluorodimethoxyborane. Hypochlorous acid. Lithium bronze. Manganesc(II) chloride-Lithium aluminum hydride. Methylenetriphenylphosphorane. Organotitanium reagents. Tetrakis(triphenylphosphine)palladium. Tin. Tin(II) fluoride. 

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