Arsenic tetroxide

Arsenous arsenate [12505-65-6] (arsenic dioxide, arsenic tetroxide), AS2O4, is known and probably corresponds to As(AsO. ... 

Arsenic Tetroxide ( ), As204.—Attempts to isolate this oxide have proved unsuccessful, but a number of products have been described... 

Arsenic Suboxide—Arsenious Oxide Polymorphism and Physical Properties of Arsenious Oxide, Chemical Properties, Uses—The Arsenites—Arsenic Tetroxide. 

Other examples are the use of osmium(VIII) oxide (osmium tetroxide) as catalyst in the titration of solutions of arsenic(III) oxide with cerium(IV) sulphate solution, and the use of molybdate(VI) ions to catalyse the formation of iodine by the reaction of iodide ions with hydrogen peroxide. Certain reactions of various organic compounds are catalysed by several naturally occurring proteins known as enzymes. 

Method A Standardisation with arsenic (III) oxide. Discussion. The most trustworthy method for standardising cerium(IV) sulphate solutions is with pure arsenic(III) oxide. The reaction between cerium(IV) sulphate solution and arsenic(III) oxide is very slow at the ambient temperature it is necessary to add a trace of osmium tetroxide as catalyst. The arsenic(III) oxide is dissolved in sodium hydroxide solution, the solution acidified with dilute sulphuric acid, and after adding 2 drops of an osmic acid solution prepared by dissolving 0.1 g osmium tetroxide in 40mL of 0.05M sulphuric acid, and the indicator (1-2 drops ferroin or 0.5 mL /V-phenylanthranilic acid), it is titrated with the cerium(IV) sulphate solution to the first sharp colour change orange-red to very pale blue or yellowish-green to purple respectively. 

Procedure. Weigh out accurately about 0.2 g of arsenic(III) oxide, previously dried at 105-110 °C for 1-2 hours, and transfer to a 500 mL beaker or to a 500 mL conical flask. Add 20 mL of approx. 2M sodium hydroxide solution, and warm the mixture gently until the arsenic(III) oxide has completely dissolved. Cool to room temperature, and add 100 mL water, followed by 25 mL 2.5M sulphuric acid. Then add 3 drops 0.01 M osmium tetroxide solution (0.25 g osmium tetroxide (CARE FUME CUPBOARD) dissolved in 100 mL 0.05M sulphuric acid) and 0.5 mL AT-phenylanthranilic acid indicator (or 1-2 drops of ferroin). Titrate with the 0.1 M cerium(IV) sulphate solution until the first sharp colour change occurs (see Discussion above). Repeat with two other samples of approximately equal weight of arsenic(III) oxide. 

Reaction between arsenic(tll) and chlorate is fairly slow. Although the reaction can be markedly accelerated by osmium tetroxide as catalyst , the quantitative reduction of chlorates takes nearly an hour. In the case of the induced reaction it was assumed that arsenic(III) is oxidized to arsenic(IV) by 1-equivalent oxidizing agents. Chlorate is reduced to chlorine dioxide by the arsenic(IV) intermediate, viz. 

During the induced reduction of chlorate a considerable oxygen effect was observed. The air oxidation of arsenic(ril) is also an induced reaction, the extent of which decreases with increasing acid concentration and is increased by decreasing the rate of primary reaction. The induced oxidation caused by air also can be observed during the osmium tetroxide-catalyzed chlorate-arsenic(III) reaction. 

Temperature and air feed is carefully controlled in the process to suppress any formation of antimony tetroxide (86204). Antimony trioxide is separated from any arsenic trioxide (AS2O3) that may be present as an impurity by volatilization, as the latter is much more volatile than the former. It may be also prepared by alkaline hydrolysis of antimony trichloride and subsequent dehydration of hydrous oxide under controlled heating (rapid or vigorous heating may partially oxidize 8b(III) to Sb(V). 

P listed wastes Highly toxic chemicals that are rarely used, are banned, or are permitted for limited uses Acrolein, arsenic trioxide, dieldrin, heptachlor, me-thiocarb, osmium tetroxide, 2-propenal... 

Oils Miscellaneous Linseed Dibutyl Phthalate Dioctyl Phthalate Arsenic Disulfide Arsenic Disulfide Arsenic Disulfide Cleic Acid Arsenic Disulfide Nitrogen Tetroxide 4-Chloro-O-Toluidine Asphalt Blending Stock... 

Two well-defined oxides are known arsenious oxide, As2Oa, and arsenic pentoxide, As2Os. The former is the most important compound of arsenic, being the form in which the element is most used. A suboxide, As20, and a tetroxide, As204, have been described, but the existence of neither as a pure compound has been established. 

The solubility is greater in concentrated arsenious acid solution and there is evidence that the tetroxide exists in the form of arsenious arsenate,7 AsAs04. 

Osmium tetroxide catalytically assists the oxidation of certain oxidisable substances. For example,8 a mixture of 15 grams of arsenic with 10 grams of potassium chlorate in 50 e.c. of water remains unaltered even after addition of a few drops of dilute sulphuric acid. Upon introducing a trace of osmium tetroxide (c. 0-015 gram) in solution, the temperature immediately rises, the arsenic being rapidly oxidised to... 

Catalysts are very important to the analytical chemist in a number of reactions that are normally too slow to be analytically useful. An example is the use of an osmium tetroxide catalyst to speed up the titration reaction between arsenic(III) and ceiium(IV), whose equilibrium is very favorable but whose rate is normally too slow to be useful for titrations. The measurement of the change in the rate of a kineti-cally slow reaction in the presence of a catalyst can actually be used for determining the catalyst concentration. 

Some reactions in which one half-reaction is irreversible do occur rapidly. Several oxidizing and reducing agents containing oxygen are reduced or oxidized irreversibly but may be speeded up by addition of an appropriate catalyst. The oxidation of arsenic(ni) by cerium(IV) is slow, but it is catalyzed by a small amount of osmium tetroxide, OSO4. 

Cerium(IV) solutions can be standardized against primary standard AS2O3, Na2C204, or electrolytic iron. The reaction with arsenic(III) is slow, and it must be catalyzed by adding either osmium tetroxide (OSO4) or iodine monochloride (ICl). Ferroin is used as the indicator. The reaction with oxalate is also slow at room temperature, and the same catalyst can be used. The reaction is rapid, however, at room temperature in the presence of 2 M perchloric acid. Nitroferroin is used as the indicator. 

The roasted mass should contain the tetroxide principally, if the ore is comparatively pure and if the correct temperature and proper quantity of air have been maintained throughout the process of roasting. But ideal conditions are very seldom met with hence the product may contain antimony glass, undecomposed sulphide, and antimoniates, arseniates, and sulphates of foreign metals, if the ore contains these foreign sulphides and arsenic compounds. 

Poisons Cyanide, osmium tetroxide, phosphorus, sodium azide Arsenic compounds, phosphorus, osmium tetroxide... 

Cyanides, phosgene, CI2, osmium tetroxide, arsenic compounds... 

Refinery slag generally contains from 20 to 60 per cent, of antimony, and is a mixture of soda, sodium sulphantimaaiate, antimony trioxide and tetroxide, ferrous oxide, iron sulphide, arsenic oxide, and smaller proportions of silica and alumina it is added to charges of ore. 

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