Arsenic arsine

Arsenic Arsine Asbestos Azelaic acid Aziridine Azo dyes... 

Arsenic trichloride Gallium arsenide Potassium arsenate Arsine Arsenic add Sodium arsenate Sodium arsenite CaicKjm arsenate Arsenic trioxide Arsenic pwtoxide Arsenic bisulphide Arsenic pentasulphide Arsenic hemiselenide... 

SILVER ALUMINUM ALUMINUM OXIDE ARSENIC ARSINE... 

Pentavalent hydrides of arsenic are not known in any form. The simplest hydride of arsenic , arsine (AsHs) is a very toxic gas (m.p. -116°C, b.p. —62°C) with a characteristic garlic-like odor, which in the presence of air oxidizes to AS4O6. It is thermally unstable depositing a mirror of As in hot smfaces, a property that is nsed in the qualitative determination of arsenic (Marsh test). 

Ores of arsenic orpiment, realgar, arsenolite, arsenopyrite. Compounds of arsenic arsine, arsenic trioxide, arsenious acid, cupric hydrogen arsenite, arsenic pentoxide, arsenic acid, sodium arsenate. The Marsh test for arsenic. U.ses of arsenic and its compounds lead shot, insecticides, weed killers, chemotherapy. 

Section II Arsenic Arsine Lead Mercury Section III BAL (Dimercaprol) EDTA, Calcium (Calcium Disodium EDTA, Calcium Disodium Edetate, Calcium Disodium Versenate) Succimer (DMSA) Unithiol (DMPS)... 

The arsenate(lll) ion can be reduced by systems which generate hydrogen (for example metal/acid) to give arsine, for example... 

Arsenic present only in traces (in any form) can be detected by reducing it to arsine and then applying tests for the latter. In Marsh s test, dilute sulphuric acid is added dropwise through a thistle funnel to some arsenic-free zinc in a flask hydrogen is evolved and led out of the flask by a horizontal delivery tube. The arsenic-containing compound is then added to the zinc-acid solution, and the delivery tube heated in the middle. If arsenic is present, it is reduced to arsine by the zinc-acid reaction, for example ... 

The evolved arsine is decomposed to arsenic and hydrogen at the heated zone of the delivery tube hence arsenic deposits as a shiny black mirror beyond the heated zone. 

The volatile hydride (arsine in Equation 15.1) is swept by a. stream of argon gas into the inlet of the plasma torch. The plasma flame decomposes the hydride to give elemental ions. For example, arsine gives arsenic ions at m/z 75. The other elements listed in Figure 15.2 also yield volatile hydrides, except for mercury salts which are reduced to the element (Fig), which is volatile. In the plasma flame, the arsine of Equation 15.1 is transformed into As ions. The other elements of Figure 15.2 are converted similarly into their elemental ions. 

Lead—antimony or lead—arsenic ahoys must not be mixed with lead—calcium (aluminum) ahoys in the molten state. Addition of lead—calcium—aluminum ahoys to lead—antimony ahoys results in reaction of calcium or aluminum with the antimony and arsenic to form arsenides and antimonides. The dross containing the arsenides and antimonides floats to the surface of the molten lead ahoy and may generate poisonous arsine or stibine if it becomes wet. Care must be taken to prevent mixing of calcium and antimony ahoys and to ensure proper handling of drosses. 

Arsenic. Total arsenic concentration can be determined by reduction of all forms to arsine (AsH ) and collection of the arsine in a pyridine solution of silver diethyldithiocarbamate. Organoarsenides must be digested in acidic potassium persulfate prior to reduction. The complex that forms is deep red, and this color can be measured spectrophotometricaHy. Reduction is carried out in an acidic solution of KI—SnCl2, and AsH is generated by addition of 2inc. 

Atomic absorption spectroscopy is an alternative to the colorimetric method. Arsine is stiU generated but is purged into a heated open-end tube furnace or an argon—hydrogen flame for atomi2ation of the arsenic and measurement. Arsenic can also be measured by direct sample injection into the graphite furnace. The detection limit with the air—acetylene flame is too high to be useful for most water analysis. 

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. 

Arsenic vapor [12187-88-5] As, does not combine direcdy with hydrogen to form hydrides. However, arsine (arsenic hydride) [7784-42-17, AsH, a highly poisonous gas, forms if an intermetaUic compound such as AlAs is hydrolyzed or treated with HQ. Arsine may also be formed when arsenic compounds are reduced using zinc in hydrochloric acid. Heating to 250°C decomposes arsine into its elements. 

Arsenic from the decomposition of high purity arsine gas may be used to produce epitaxial layers of III—V compounds, such as Tn As, GaAs, AlAs, etc, and as an n-ty e dopant in the production of germanium and silicon semiconductor devices. A group of low melting glasses based on the use of high purity arsenic (24—27) were developed for semiconductor and infrared appHcations. 

The toxicity of arsenic ranges from very low to extremely high depending on the chemical state. Metallic arsenic and arsenious sulfide [1303-33-9] AS2S2, have low toxicity. Arsine is extremely toxic. The toxicity of other organic and inorganic arsenic compounds varies (28). 

Precaution should be taken to avoid accidental generation of arsine gas the maximum permitted exposure is 0.05 ppm in air per 8-h period five days per week (34). Disposal of arsenical products should be in compliance with Eederal and local government environmental regulations. 

Arsenic Hydrides. Although there are occasionally reports of other arsenic hydrides, eg, AS2H4, AS2H2 (or AsH), and AS4H2, the only weU-characterized binary compound of arsenic and hydrogen is arsine. 

Arsine is formed when any inorganic arsenic-bearing material is brought in contact with zinc and sulfuric acid. The arsenides of the electropositive metals are decomposed with the formation of arsine by water or acid. Calcium arsenide [12255-53-7] Ca2As2, treated with water gives a 14% yield of arsine. Better yields (60—90%) are obtained by decomposing a solution of sodium arsenide [12044-25-6] Na As, in Hquid ammonia with ammonium bromide (14,15). Arsine may be accidentally formed by the reaction of arsenic impurities in commercial acids stored in metal tanks, so that a test should be made for... 

Arsine is used for the preparation of gallium arsenide [1303-00-0] GaAs, (17), and there are numerous patents covering this subject (see Arsenic and ARSENIC alloys). The conversion of a monomeric arsinogaHane to gallium arsenide has also been described (18). GaUium arsenide has important appHcations in the field of optoelectronic and microwave devices (see Lasers Microwave technology Photodetectors). 

Other Arsenic Hydrides. Diarsine [15942-63-9] AS2H4, occurs as a by-product in the preparation of arsine by treatment of a magnesium aluminum arsenide alloy with dilute sulfuric acid and also may be prepared by passing arsine at low pressure through an ozonizer-type discharge tube (19). Diarsine is fairly stable as a gas but quite unstable (above — 100°C) in condensed phases. The for diarsine is +117 4 kJ/mol (28 1 kcal/mol) and... 

Methylarsine, trifluoromethylarsine, and bis(trifluoromethyl)arsine [371-74-4] C2HAsF, are gases at room temperature all other primary and secondary arsines are liquids or solids. These compounds are extremely sensitive to oxygen, and ia some cases are spontaneously inflammable ia air (45). They readily undergo addition reactions with alkenes (51), alkynes (52), aldehydes (qv) (53), ketones (qv) (54), isocyanates (55), and a2o compounds (56). They also react with diborane (43) and a variety of other Lewis acids. Alkyl haUdes react with primary and secondary arsiaes to yield quaternary arsenic compounds (57). 

Trimethyl arsine [593-88-4] C H As, has been identified as the toxic volatile arsenical, once known as "Gosio gas," produced by the reaction of certain molds that grow on wallpaper paste and react with inorganic arsenic compounds present in the paper. A number of microorganisms can methylate arsenic trioxide and other arsenic-containing compounds to yield trimethylarsine. These microorganisms include Scopulariopsis brevicaulis Candida humicola and Gliocladium roseum (72). 

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