Arsenic acid trioxide

Arsenic Peroxides. Arsenic peroxides have not been isolated however, elemental arsenic, and a great variety of arsenic compounds, have been found to be effective catalysts ia the epoxidation of olefins by aqueous hydrogen peroxide. Transient peroxoarsenic compounds are beheved to be iavolved ia these systems. Compounds that act as effective epoxidation catalysts iaclude arsenic trioxide, arsenic pentoxide, arsenious acid, arsenic acid, arsenic trichloride, arsenic oxychloride, triphenyl arsiae, phenylarsonic acid, and the arsenates of sodium, ammonium, and bismuth (56). To avoid having to dispose of the toxic residues of these reactions, the arsenic can be immobi1i2ed on a polystyrene resia (57). 

Arsenic Acids and the Arsenates. Commercial arsenic acid, corresponds to the composition, one mole of arsenic pentoxide to four moles of water, and probably is the arsenic acid hemihydrate [7774-41-6] H AsO O.5H2O. It is obtained by treatment of arsenic trioxide with concentrated nitric acid. Solutions of this substance or of arsenic pentoxide in water behave as triprotic acids with successive dissociation constants = 5.6 x 10 , ... 

Amino-3-fluorophenol Arsenic acid and its salts Arsenic pentoxide Arsenic trioxide Asbestos (all types)... 

Arsen-oxyd, n, arsenic oxide, specif, arsenic trioxide, arsemc(III) oxide. -pra parat, n, arsenical preparation, arsenical, -probe, /, arsenic test or sample, -rohr, n, -rShre, /. arsenic tube, -rotgultigerz, n. proustite. -rubin, m. realgar, -salz, n. arsenic salt, arsensauer, a. of or combined with arsenic acid, arsenate of,... 

Arsenous Acid Anhydride Arsenous Chloride Arsenous Hydride Arsenous Oxide Anhydride Arsenous Trichloride Arsenous Trioxide Arsenowodor Arsenwasserstoff... 

Allyl alcohol Aluminum phosphide 4-Aminopyridine Arsenic acid Arsenic pentoxide Arsenic trioxide Calcium cyanide Carbon disulfide p-Chloroaniline... 

Chemically, arsenic is complex in that it can exist in a variety of forms including trivalent and pentavalent or as arsenic trioxide (computer chip manufacture) and arsenic acid. Arsenic is excreted in skin cells, sweat, hair, and fingernails, which can be seen as white transverse bands. Acute exposure to arsenic results in gastrointestinal pain, sensory loss, cardiovascular failure, and death. Chronic exposure or survival of acute exposure can cause loss of peripheral sensory function and loss of central nervous system function. Chronic arsenic exposure can also cause cancer of the lung and skin (see the chapter on arsenic). 

Arsenic acid is prepared by treating arsenic trioxide with concentrated nitric acid or by combination of arsenic pentoxide with water. The latter reaction is very slow. It is also formed when meta- or pyroarsenic acid is treated with cold water. 

Arsenic pentoxide is prepared by dehydration of crystalline arsenic acid at 200°C or above. The former is made by treating arsenic metal or arsenious oxide with nitric acid. Also, the pentoxide can be prepared by the reaction of arsenic trioxide with oxygen under pressure. 

Alternatively, it may be precipitated out from a solution of arsenous acid or arsenic trioxide in dilute hydrochloric acid by passing hydrogen sulfide into the solution ... 

Hydrolysis occurs slowly in water forming arsenic trioxide and hydriodic acid. The reaction proceeds via formation of arsenous acid which exists in equihhrium with HI ... 

Arsenous acid is a weak acid, known to exist only in solution. Its molecule has three -OH groups attached to the arsenic atom. The dissociation constant of this acid is 8.0 x ICRi at 25°C. It is produced by hydrolysis of arsenic trioxide in water. The trioxide is sparingly soluble in water and the rate of... 

Hydrazine in the presence of sulphuric acid reduces arsenic acid to a slight extent to arsine, which is subsequently oxidised to arsenic the reaction does not take place if a considerable concentration of hydrochloric acid is present.4 Arsenites, in the absence of arsenates, are not reduced by hydrazine. An aqueous solution of arsenic acid is reduced to the trioxide by hydrazine salts only after prolonged boiling.5... 

Arsenic sublimes on heating and is unchanged in dry air, but a film of oxide is formed in moist air heated in air at 180°C, arsenic forms arsenic trioxide of tine odor of garlic, poisonous insoluble in HC1 but soluble in concentrated HNOj or concentrated H2SO4 to form arsenic acid soluble in hot NaOH solution healed with chlorine forms arsenic trichloride heated with metals forms metallic arsenides. When arsenic is heated in a tube and tile vapor cooled (1) slowly (that is, in the hot part of the tube) black arsenic is formed, and this form is converted into the gray at 360°C, (2) rapidly (that is. in the cold part of the tube) yellow arsenic is formed, and this form is quickly converted into the gray by the action of light. Yellow arsenic is soluble in CS2,... 

Arsenic trioxide finds major use in the preparation of other compounds, notably those used in agricultural applications, The compounds monosodium methylarsonate. disodium methylarsonate, methane arsenic acid (cacodylic acid) are used for weed control, while arsenic acid, H3ASO4, is used as a desiccant for the defoliation of cotton crops, Other compounds once widely used in agriculture are calcium arsenate for control of boll weevils, lead arsenate as a pesticide for fruit crops, and sodium arsenite as a herbicide and for cattle and sheep dip. In some areas, arsenilic acid has been used as a feed additive for swine and poultry. Restrictions on these compounds vary from one country and region to the next. 

Refined arsenic trioxide is used both as a fining and decolorizing agent in glass, As Og and arsenic acid are used in the manufacture of chroma ted copper arsenate, which is used extensively as a wood preservative. 

Before 1914, the US imported most metallic arsenic from Germany (e.g., Smith, 1945). From 1914 to about 1930, the bulk of the arsenic production in the US (marketed for commercial applications as As203, arsenic trioxide, or white arsenic) was derived as a metallurgical by-product of the smelting of copper, lead, and gold. Arsenic trioxide was used in the production of fertilizers, herbicides, and insecticides (Kirk-Othmer, 1992 Ullman s Encyclopedia, 1998), or if transformed to arsenic acid, used in the manufacture of CCA, a preservative of wood products (Mineral Commodity Summaries, 2004). Arsenic metal is also used for solders, ammunition, anti-friction additive to bearings, and in the computer and electronics industry for semiconductors (Mineral Commodity Summaries, 2004). 

In the case of lead arsenate (acid form), calcium arsenate, and sodium arsenate, the Pb-isotopic compositions closely match those of sulfides from porphyry copper deposits from southeastern Arizona, specifically from the Pima and Silver Bell districts (Bouse et al., 1999). Notably, other major historical producers of arsenic trioxide (e.g., Anaconda Copper Co., US Smelting Co., Jardine Mining Co.) used... 

The elements, like phosphorus, all combine readily with 02, and they react readily with halogens and some other nonmetals. They are unaffected by dilute nonoxidizing acids, but with nitric acid As gives arsenic acid, Sb gives the trioxide and Bi dissolves to form the nitrate. 

Arsenic trioxide is the anhydride of arsenous acid, H3 AsOs. The solubility of arsenic trioxide in water at 25 °C is 21.6gL. The rate of dissolution of the trioxide in water is painstakingly slow, sometimes requiring up to 50 h of continuous agitation. The free acid has never been isolated. The solubiUty of arsenic trioxide increases greatly and occurs much more rapidly in both acid and alkaline media. 

Arsenic Trioxide (Arsenous Acid, Arsenous Acid Anhydride, Arsenious Oxide, Arsenic Sesqui-oxide. White Arsenic). AS2O3, mw 197.82 ... 

Arsenic is inert at room temperature, but ignites when heated, burning with a lavender flame to produce white clouds of the trioxide. It is oxidized to arsenic acid, HgAsO, by hot nitric acid and other powerful oxidizing agents. Arsenic combines with many other elements, both metallic and non-metallic. 

Arsenic pentoxide, AsgO, is not obtained by burning arsenic, but can be made by boiling arsenic trioxide with concentrated nitric acid. With water it forms arsenic acid. HgAsO, which is closely similar to... 

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