Nickel arsenites

Nickel Arsenite, 3NiO. As,Oa. 4H.20, is obtained as a green precipitate on addition of an alkali arsenite to a solution of a nickel salt.2... 

Several nickel arsenites [66GME] have been identified, but there are very limited chemical thermodynamic data for these solids. Chukhlantsev [57CHU] dissolved samples of nickel orthoarsenite in dilute nitric acid solutions at 20°C over 12 hours to form solutions with aqueous nickel concentrations of 8.7 x 10 mol-dm at a pH value of 6.75 and 3.1x10 at a pH value of 7.10 mol dm The author did not report a solubility product based on their measurements but, as discussed in Appendix A, if the dissolution of the solid is assumed to correspond to the reaction ... 

The proximal mechanism for induction of stress protein synthesis leading to the activation of HSF and gene activation is not completely understood, but evidence for several possibilities exists. Activation of HSF by prooxidants does not result in the accumulation of specific stress proteins (Bruce et al. 1993). These results suggest that induction of stress proteins by specific metals, whose toxicity is mediated via oxidative damage to membranes or DNA, may be fundamentally different from that of the heat-induced activation of the stress response (Keyse and Tyrrell 1987 Bruce et al. 1993). Thus, metals such as cadmium, mercury, nickel, arsenite, copper, lead, and iron, which induce oxygen free radicals or promote formation of lipid peroxides (Stacey and Klaassen 1981 Halliwell and Gutteridge 1984 Christie and Costa 1984 Kasprzak 1991 Donati et al. 1991), may... 

Geminal dihalides undergo partial or total reduction. The latter can be achieved by catalytic hydrogenation over platinum oxide [512], palladium [512] or Raney nickel [63, 512], Both partial and total reduction can be accomplished with lithium aluminum hydride [513], with sodium bis(2-meth-oxyethoxy)aluminum hydride [514], with tributylstannane [503, 514], electro-lytically [515], with sodium in alcohol [516] and with chromous sulfate [193, 197]. For partial reduction only, sodium arsenite [220] or sodium sulfite [254] are used. 

Lee-Chen SF, Yu CT, Wu DR, et al. 1994. Differential effects of luminol, nickel and arsenite on the rejoining of ultraviolet light and alkylation-induced DNA breaks. Environmental and Molecular Mutagenesis 23 116-120. 

Lead arsenite is readily obtained by an electrolytic process.6 The eatholyte may be a 15 per cent, solution of sodium hydroxide or of a sodium salt, or a 30 per cent, solution of potassium hydroxide, the cathode being of nickel. The anolyte is a solution of an alkali arsenite neutralised towards phenolphthalein by means of acetic acid, and the anode is of lead. The cathode space is separated by a diaphragm of vegetable parchment. Ormont obtained a current yield of 97 per cent., and the average energy yield amounted to 1 kg. per kilowatt-hour. 

Sodium orthoarsenate is also obtained electrolytically by the method described under calcium arsenate (p. 198). Yields up to 100 per cent, may be obtained 9 by employing a cell with a diaphragm between iron electrodes. The anolyte should contain sodium arsenite, or sodium hydroxide and arsenious oxide (equivalent to 150 g. As2Os per litre), and the catholyte sodium hydroxide (150 g. per litre). With a current density of 3 amps, per sq. dm. the current efficiency is 100 per cent. A solid crust of sodium arsenate forms around the anode. The process may be rendered continuous by circulating the anolyte and removing the precipitated arsenate. Iron or nickel electrodes are... 

In spite of the fact that ISEs for more than 60 ions have been described so far, recent findings imply that these ISEs should be re-characterized and re-optimized for trace level applications [19]. The list of ISEs with low-level LODs needs to be expanded either by re-characterization of existing ionophores or by synthesis of new ones. Important ions for which low LODs have yet to be demonstrated are, for example, mercury, chromium, nickel, arsenate and arsenite ions. Hopefully, synthetic chemists will rise to the challenge and new, selective ionophores will be developed that will achieve this goal. 

By Direct Replacement on Tetracarbonyinickel. This was the first way by which nickel(O) carbonyl derivatives, different from Ni(CO)4, were obtained with tertiary phosphines, arsines, stibines 160) j and bismutines 17) j and with triarylphosphites 131) and arsenites 17). 

Puschel and Stefanac ° use alkaline hydrogen peroxide in the oxygen flask method to oxidize arsenic to arsenate. The arsenate is titrated directly with standard lead nitrate solution with 4-(2-pyridylazo) resorcinol or 8-hydroxy-7-(4-sulpho-l-naphthylazo) quino-line-5-sulphonic acid as indicator. Phosphorus interferes in this method. The precision at the 99% confidence limit is within 0.67% for a 3-mg sample. In another variation, Stefanac used sodium acetate as the absorbing liquid, and arsenite and arsenate are precipitated with silver nitrate. The precipitate is dissolved in potassium nickel cyanide (K2Ni(CN)4) solution and the displaced nickel is titrated with EDTA solution, with murexide as indicator. The average error is within + 0.19% for a 3-mg sample. Halogens and phosphate interfere in the procedure. 

Since 1910 the method of Bart has been modified by a number of investigators, Bart, himself, being the first to improve the reaction. He found that coupling of aryldiazonium compounds with alkali arsenites is catalyzed by copper salts and by silver or copper powder. In a later patent the use of metallic catalysts, copper, nickel, or cobalt, as well as their salts is said to facilitate the removal of diazo nitrogen at low temperatures and to obviate the formation of by-products. Though many have since observed that the coupling reaction is speeded by the use of the above catalysts, no systematic study has been made to determine the effect of such catalysts on the final yield. 

The principal ore of arsenic (5 x 10 % of earth s crust) is arsenical pyrites, FeAsS, but the element occurs commonly with nickel, copper and tin As40g is recovered from flue-dusts collected during the extraction of these metals. Sublimation in the presence of galena, which prevents the formation of arsenites, purifies the oxide this is reduced to arsenic with carbon in a cast iron retort. The element itself has few uses about 0.5% added to lead increases the surface tension of the molten metal and allows spherical lead-shot to be produced. The principal commercial form is the so-called white arsenic, As Og. Arsenic compounds are used mainly for their toxicity arsenical insecticides have been much used. 

The growth of the bacterium is inhibited by benzoic acid, sorbate, and sodium laurylate (Onysko et al., 1984), and nitrate at 50 mM inhibits completely the oxidation of ferrous ion by the bacterium (Eccleston et al., 1985). Although the bacterium is sensitive to chloride ion, it becomes resistant to 140 pM chloride ion by training (Shiratori and Sonta, 1993). The bacterium is fairly resistant to heavy metal ions its activity to oxidize ferrous ion is scarcely inhibited in the presence of 65 mM cupric ion, 100 mM nickel ion, 100 mM cobalt ion, 100 mM zinc ion, 100 mM cadmium ion, and 0.1 mM silver ion (Eccleston et al., 1985). The bacterium acquires the ability to grow even in the presence of 2 mM uranyl ion (Martin et al., 1983). Furthermore, it becomes resistant to arsenate and arse-nite by training a strain of the bacterium has been obtained which oxidizes ferrous ion in the presence of 80 mM arsenite and 287 mM arsenate (Collinet and Morin, 1990 Leduc and Ferroni, 1994). The resistant ability of the bacterium to arsenite and arsenate is important when they are applied for the solubilization of arsenopyrite (FeAsS) [reactions (5.8) and (5.9)]. Leptospirillum ferrooxidans is generally more sensitive to heavy metal ions than A. ferrooxidans (Eccleston et al., 1985). 

The reduction of 6-chloro-2(IH)-hydroxyquinoxaline-4-oxides can be completed by chemical reduction or catalytic hydrogenation. The successful chemical reduction has been reported using triphenylphosphine alone or in conjunction with iron, zinc, tin, sodium arsenite, ammonium sulfide, or sodium dithionite under alkaline conditions. This route is fairly expensive and gives low yields, large aqueous wastes and product isolation difficulties. A similarly expensive process employs hydrazine in the presence of Raney nickel catalyst in alkaline conditions. The reported yields range from 88 to 96%. Additional work with Raney nickel uses very low pressures of hydrogen in place of hydrazine. The yields are comparable. 

Lee-Chen SF, Yu CT, Jan KY (1992) Effect of arsenite on the DNA repair of UV-irradiated Chinese hamster ovary cells. Mutagenesis 7 51-55 Li Y, Togashi Y, Sato S, Emoto T, Kang J-H, Takeichi N, Kobayshi H, Kojima Y, Une Y, Uchino J (1991) Abnormal copper accumulation in non-cancerous and cancerous liver tissues of LEC rats developing hereditary hepatitis and spontaneous hepatoma. Jpn J Cancer Res 82 490-492 Lin XH, Sugiyama M, Costa M (1991) Differences in the effect of vitamin E on nickel sulfide or nickel chloride-induced chromosomal aberrations in mammalian cells. Mutat Res 260 159-164... 

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