Cobalt hydrogen arsenate

The extraction of cobalt from arsenical concentrates consisting of autooxidation acid leaching under pressure, separation, purification, hydrogen reduction of ammoniacal leach solution, and removal of sulfur and granulation of the metal was described by Mitchell (M37). The final product contained 95.6% cobalt, 3.90% nickel, and 0.03% arsenic compared to the feed concentrate with an assay of 17.5% cobalt, 1% nickel, and 24% arsenic. 

Copper sulfate, in small amounts, activates the zinc dust by forming zinc—copper couples. Arsenic(III) and antimony(TTT) oxides are used to remove cobalt and nickel they activate the zinc and form intermetaUic compounds such as CoAs (49). Antimony is less toxic than arsenic and its hydride, stibine, is less stable than arsine and does not form as readily. Hydrogen, formed in the purification tanks, may give these hydrides and venting and surveillance is mandatory. The reverse antimony procedure gives a good separation of cadmium and cobalt. 

OxideofOoba.lt, the ores of which, after grinding and roasting, to drive off as much as possible the excess of arsenic and sulphur, are dissolved in hydrochloric add, sometimes with the addition of a small quantity of nitric acid. The copper, lead, silver, arsenic, antimony, el cetera, are precipitated by sulphide of hydrogen, and to the filtered solution carbonate of lime is added in (he form of chalk, by which all the iron, alumina, and a trace ot cobalt are thrown down, the nickel and cobalt remaining in solution. To this solution which must ho hot and neutral, a solutien of bleaching powder is added in sufficient quantity to precipitate the cobalt, and the menstruum is then well boiled to remove the chlorine as fast as possible. The oxide of nickel is afterwards precipitated from the filtrate by the addition of hydrate of lime, and ebullition. 

Standard lead-acid batteries lose a small amount of water by evaporation, but the major mechanism for water loss is by electrolysis to form hydrogen and oxygen, as described by eqs (5.5) and (5.6). The presence of small quantities of foreign elements lowers the overvoltages for these processes and leads to an accelerated water loss it has been shown that the elements antimony, arsenic, cobalt, manganese, nickel, platinum and tellurium all have a deleterious effect, even at low levels. Two general approaches have been taken in the development of MF batteries ... 

The submitters of the synthesis analyzed these compounds for ammonia by the method of Horan and Eppig [J. Am. Chern. Soc., 71, 581 (1949)]. This involves heating the sample in excess alkali and determining the amount of ammonia liberated. Arsenic (III) oxide is added to prevent oxidation of the ammonia by the cobalt (III). In the hands of the checkers, however, this method gave low results. Analysis for carbon, hydrogen, and cobalt by the microcombustion procedures is difficult but gives satisfactory results. 

Liebig s procedure 2 consists in heating the finely divided ore to redness with potassium hydrogen sulphate until fumes cease to be evolved. On cooling, the mass contains a soluble double sulphate of cobalt and potassium, which can be extracted with water, leaving a residue containing insoluble compounds, mainly oxides and arsenic derivatives of iron, nickel, and some cobalt.3... 

Tri-cobalt Di-arsenide, Co3As2, may be prepared by the action of arsenic chloride on metallic cobalt at 800-1400° C. or by heating mixtures of arsenic and cobalt in hydrogen or carbon monoxide at this temperature. It is also formed when powdered cobalt is heated in hydrogen containing arsenic vapour, and when cobalt arsenate or arsenite is reduced by hydrogen at 900° C. Its density is 7-82, and it loses arsenic when strongly heated.1... 

The most prominent geochemical difference, and one that has been exploited in the classification of manganese deposits (see, e.g., Nicholson (1992)), is the extreme concentration of the heavy metals such as cobalt, nickel, and copper in the hydrogenous deposits. A comparison of the analyses in Table 2 for hydrogenous deposits to those for ancient deposits plus modern hydrothermal deposits shows a 10-fold or higher enrichment in the hydrogenous deposits for cobalt, nickel, and copper, but also for lead, thorium, and total rare earth elements (REEs). The ancient deposits and the modem hydrothermal deposits are similar for most elements the ancient deposits show some enrichment in sulfur, arsenic, and selenium, whereas the modem hydrothermal deposits are relatively enriched in nickel, copper, and molybdenum. 

A Ni-As(B) catalyst prepared by the borohydride reduction of alumina-supported nickel arsenate gave, on hydrogenation of 1-bromo-l 1-hexadecyne (13) in the presence of a small amount of acetone, a 97% yield of the alkene (14) having a 92 5 cis/trans ratio. No hydrogenolysis of the carbon-bromine bond occurred. "> 2 Borohydride reduction of cobalt acetate gave a Co(B) catalyst that was somewhat less active than Ni(B) but that was quite selective in alkyne semihydrogenations (Eqn. 16.20). ... 

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