Arsenic sulfur oxides

Arsenates are oxidizing agents and are reduced by concentrated hydrochloric acid or sulfur dioxide. Treatment of a solution of orthoarsenate with silver nitrate in neutral solution results in the formation of a chocolate-brown precipitate of silver orthoarsenate, Ag AsO, which may be used as a test to distinguish arsenates from phosphates. With hydrofluoric acid, orthoarsenate solutions yield hexafluoroarsenates, eg, potassium hexafluoroarsenate [17029-22-0] (KAsFg)2 H2O. Arsenates of calcium or lead are used as insecticides sodium arsenate is used in printing inks and as a mordant. 

Trialkyl- and triarylarsine sulfides have been prepared by several different methods. The reaction of sulfur with a tertiary arsine, with or without a solvent, gives the sulfides in almost quantitative yields. Another method involves the reaction of hydrogen sulfide with a tertiary arsine oxide, hydroxyhahde, or dihaloarsorane. X-ray diffraction studies of triphenylarsine sulfide [3937-40-4], C gH AsS, show the arsenic to be tetrahedral the arsenic—sulfur bond is a tme double bond (137). Triphenylarsine sulfide and trimethylarsine sulfide [38859-90-4], C H AsS, form a number of coordination compounds with salts of transition elements (138,139). Both trialkyl- and triarylarsine selenides have been reported. The trialkyl compounds have been prepared by refluxing trialkylarsines with selenium powder (140). The preparation of triphenylarsine selenide [65374-39-2], C gH AsSe, from dichlorotriphenylarsorane and hydrogen selenide has been reported (141), but other workers could not dupHcate this work (140). 

Sulfuric acid manufacture released both sulfur oxides and arsenic into the environment. 

As seen in the above equations, the aqueous oxidation processes convert sulfur in the feed to dissolved sulfate, while arsenic is oxidized and precipitated as ferric arsenate compounds. So, problems of the emission of sulfur and arsenic oxides caused by roasting are avoided in the aqueous oxidation processes. The two different industrial methods which achieve the oxidation reactions are pressure oxidation and biological oxidation. 

Emissions from sinter plants are generated from raw material handling, windbox exhaust, sinter discharge (associated sinter crushers and hot screens), and from the cooler and cold screen. The primary source of particulate emissions, mainly irons oxides, magnesium oxide, sulfur oxides, carbonaceous compounds, aliphatic hydrocarbons, and chlorides, are due to the windbox exhaust. Contaminants such as fluorides, ammonia, and arsenic may also be present. At the discharge end,... 

Primary copper processing results in air emissions, process wastes, and other solid-phase wastes. Particulate matter and sulfur dioxide are the principal air contaminants emitted by primary copper smelters. Copper and iron oxides are the primary constituents of the particulate matter, but other oxides, such as arsenic, antimony, cadmium, lead, mercury, and zinc, may also be present, with metallic sulfates and sulfuric acid mist. Single-stage electrostatic precipitators are widely used in the primary copper industry to control these particulate emissions. Sulfur oxides contained in the off-gases are collected, filtered, and made into sulfuric acid. 

Volatile decomposition products may include HC1, HBr, HF, and nitrogen oxides (NO ) or sulfur oxides (SO ). Decomposition vapors from nitrogen vesicants may form explosive mixtures in air. In addition, a corrosive and toxic residue may remain. HL (C03-A010) will also produce toxic arsenic oxides. 

Arsenic(III) fluoride is prepared by reacting arsenic(III) oxide with hydrogen fluoride, with calcium fluoride and sulfuric acid, or with fluorosulfonic acid.12... 

Jackson et al. (2003) studied the oxidation reaction rates of a gersdorffite specimen with the composition of Ni0.68Fe0.19Co0.14As1.08S0.92- The oxidation rate of the mineral was more than 10 times greater in aerated water than air, and arsenic was more reactive than sulfur. As-, As+, As3+, and As5+ were detected in the surface oxidation products in the presence of either air or aerated water. After 5 hours of exposure to air, As+ and As3+ were measured on the surface of the gersdorffite. As5+ was finally detected after a total of 10 hours of air exposure (Jackson et al., 2003), 899. In aerated distilled water, As3+ and As5+ were the dominant arsenic surface oxidation products after only 15 minutes (Jackson et al., 2003), 897. 

Both Reactions 3.50 and 3.51 indicate that sulfur oxidizes before iron and that As(I-) and As(0) in arsenopyrite oxidize to As(III). Nevertheless, (Craw, Falconer and Youngson (2003), 81) warn that higher than expected pH readings in their experimental data suggest that at least Reaction 3.50 may be a too simplistic description of arsenopyrite oxidation. Some of the arsenic from arsenopyrite may fully oxidize to As(V) rather than existing as H3As03° as predicted by Reaction 3.50. Using X-ray photoelectron spectroscopy (XPS), Nesbitt and Muir (1998) confirmed that As(III) is not the only arsenic species in surface oxidation products on arsenopyrite. As(V) and even traces of As(I) are also present. 

Evidence for exchange of arsenic-carbon with arsenic-oxygen and arsenic-sulfur bonds, respectively, is obtained from the thermal dispor-portionation of methylarsenous oxide (143) according to Eq. (154), of phenyl-arsenous oxide according to Eq. (155), and of alkyl or arylarsenous sulfides according to Eq. (156). 

Although Moissan prepared arsenic (III) fluoride by the action of fluorine on arsenic and on arsenic (III) chloride,1 the only convenient laboratory procedure involves distillation of a mixture of arsenic (III) oxide, calcium fluoride, and concentrated sulfuric acid.2 University of Illinois, Urbana, Bl. t University of Michigan, Ann Arbor, Mich. 

A dried intimate mixture of 23.4 g. of reagent-grade calcium fluoride (0.30 mol) and 19.8 g. of arsenic(III) oxide (0.10 mol) is introduced into the reaction flask.f To this, 98.1 g. of reagent-grade concentrated sulfuric acid (0.95 mol) is added. The apparatus is then assembled, and the mixture is heated slowly on a water bath to distill the product as it is formed. 

The oxidation of arsenopyrite [FeAsS] releases both sulfur and arsenic. Buckley and Walker (1988) studied the oxidation of arsenopyrite in alkaline and in acidic aqueous solutions. In air, the mineral reacted rapidly, and the oxidation of arsenic to As(III) was more rapid than the oxidation of iron on the same surface. Only a small amount of sulfur oxidation occurred. Under acidic conditions, the mineral formed sulfur-rich surfaces. 

In the first example, the ratio of the masses of oxygen in the two compounds, for a given mass of carbon, was 1 2. In the second example, the ratio of the masses of sulfur in the two compounds, for a given mass of arsenic, was 2 3. Today, we know that the carbon oxides are CO (carbon monoxide) and CO2 (carbon dioxide), and the arsenic sulfides are AS4S4 and AS2S3. Dalton could not have known this, however, because he had no information from which to decide how many atoms of carbon and oxygen are in one molecule of the carbon-oxygen compounds or how many atoms of arsenic and sulfur are in the arsenic-sulfur compounds. 

Oxidation of alcohol, carbonyl and acid functions, hydroxylation of aliphatic carbon atoms, hydroxylation of alicyclic carbon atoms, oxidation of aromatic carbon atoms, oxidation of carbon-carbon double bonds, oxidation of nitrogen-containing functional groups, oxidation of silicon, phosphorus, arsenic and sulfur, oxidative N-dealkylation, oxidative O- and S-dealkylation, oxidative deamination, other oxidative reactions... 

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