Arsenic acid Hydrates

X 10 , and A3 = 3.0 x 10 . Hydrated arsenic acid loses water when heated at about 100°C with the formation of pyroarsenic acid [13453-15-1/, H4AS2O2. At higher temperatures additional water is lost to yield metaarsenic acid [10102-53-1/, HAsO. Arsenates derived from each of these acids are known. Treatment of a meta- or pyroarsenate with cold water gives the orthoarsenate. 

Arsenic acid (arsenic pentoxide hydrate, arsenic V oxide hydrate, orthoarsenic acid) [12044 50-7] M 229.8 + XH2O, pKj 2.26, pK 6.76, pKj 11.29 (H3ASO4). Cryst from cone solns of... 

Vanadyl Arsenates.—Two of these have been prepared by the action of hydrated hypovanadic oxide on solutions of arsenic acid 2V02.2As206.3H20 and 2V02.3As205.6H20. They are both sky-blue, crystalline compounds, and the latter rapidly becomes green on exposure to air.1... 

If the tetrahydrate is kept for some time in a superfused state, the (3, d)-hydrate is formed as a hard white crystalline scale,5 and this hydrate may also be obtained 6 by evaporating a solution of arsenic acid in an open vessel at temperatures from 50° to 100° C. or under increased pressure at 150° C. 

Properties of Aqueous Solutions of Arsenic Acid.—The system As,Oj-H20 has been investigated 11 by determining the solubility curves of the (1, 4)- and the (3, 5)-hydrates, and also the curve for the depression of the freezing point of water. The data obtained are given in the following table and are graphically represented in fig. 10. 

Cadmium Arsenates.—The hydrated normal cadmium orthoarsenate, 2Cd3(As04)2.3H20, falls as a white voluminous precipitate on adding alkali to a solution of cadmium mono- or di-hydrogen arsenate in hydrochloric acid,4 or on addition of sodium orthoarsenate to a solution of cadmium sulphate.5 On drying at 100° C. the anhydrous salt remains. 

Lithium Arsenates.—Lithium Orthoarsenate is obtained as the hemihydrate, 2Li3As04.H30, by the action of lithium carbonate on arsenic acid and allowing the solution to crystallise.4 The anhydrous salt is prepared by recrystallising this hydrate from fused lithium chloride 5 rhombic crystals of density 3-07 at 15° C. are obtained. These are soluble in dilute acetic acid they are extremely stable and may be heated to a white heat without fusion. With excess of arsenic acid the normal salt yields deliquescent rhombic prisms of lithium dihydrogen arsenate, 2LiH2As04.3H20, which with water revert to the normal salt.6... 

Molybdenum Arsenates and Molybdo-arsenates.—Molybdous Arsenate, Mo(HAs04)2.wH20( ), is said1 to be formed as a grey precipitate when molybdous chloride is treated with sodium monohydrogen arsenate the precipitate first redissolves, hut afterwards becomes permanent. Molybdic arsenate, obtained in a similar manner from molybdic chloride, has been described by Berzelius, who also considered that an acid salt was produced on dissolving the hydrate of molybdenum dioxide in excess of arsenic acid, since the solution turned blue on standing.1... 

Arsenic Pentoxide—Hydrates of Arsenic Pentoxide—Manufacture of Arsenic Acid—Properties of Arsenic Acid Solutions—The Arsenates—Perarsenates. 

Drum dryers potatoes, cereals, buttermilk, skim milk, dextrins, yeasts, instant oat meal, polyacylamides, sodium benzoate, propionates, acetates, phosphates, chelates, aluminum oxide, m-disulfuric acid, barium sulfate, calcium acetate-arsenate-carbonate-hydrate-phosphate, caustic, ferrous sulfate, glue, lead arsenate, sodium benzene sulfonate, and sodium chloride... 

Cellulose is insol in w, ale, eth all known simple org solvs. The best solv for it is cuprammonium hydroxide, [Cu(NH3)4(OH)2], also called Schweitzer s Reagent. It is also sol in a coned soln of Ca thiocyanate alone or in combination with formaldehyde. Other solvs gelatinizers for cellulose include zinc chloride (in 40% soln on heating), basic beryllium perchlorate, 84% phosphoric acid, selenic acid, arsenic acid, sulfurous acid, 66% HBr, 70-75% HF, coned HI, chloral with pyridine, chloral hydrate in H2S04, and inorg salts(such as NaCl) in coned solns at high temps. Coned solns of NaOH at ca -10° only partially dissolve cellulose while the remainder is swelled "mercerized . 

The hydrated oxide possesses oxidising powers, arsenious acid being oxidised to arsenic acid, hydrogen iodide to iodine, whilst hydrogen gas raises the oxide to incandescence, water being formed. 

Sodium arsenate (01m). Dissolve 31 2 g disodium hydrogen arsenate hepta-hydrate, Na2HAs04.7H20, in water to which 10 ml concentrated hydrochloric acid was added. Dilute the solution to 1 litre. 

SYNS AMMONIUM MAGNESIUM ARSENATE AxMMONIUM L GNESIUM ARSENATE DIHYDRATE ARSENIC ACID, AMMONIUM MAGNESIUM SALT, HYDRATE (1 1 1 2) ARSENIC ACID (H3-AS-04),. AMMONIUM MAGNESIUM SALT, (1 1 1) MAGNESIUM AMMONIUM ARSFJSIATE... 

The free oxy-acids of antimony are even less stable than those of arsenic. Various hydrated forms of the trioxide and pentoxide have been described as antimonious and antimonic acids, but their structures are unknown. Finite oxy-ions SbO ", SbOJ, and Sb207 do not exist. Compounds formerly described as ortho-, meta-, and pyro-antimonates all contain Sb " octahedrally coordinated by oxygen, either as Sb(OH)g ions, in compounds which were once described as hydrated meta- or pyro-antimonates, or as SbOg groups in the compounds of type (b), which are best described as complex oxides, and not as antimonates, for reasons given later. 

I. and 8, and with most of the metals. With H it only combinee when that element is in the nascent state. Warm, concentrated HyB9i ia decomposed by As with formation of SO, A O, and H,0. Nitric add is leadily decomposed, giving up its O to tlxe formation of arsenic acid. With hot HCl, arsenic triohloride is formed. When fused with potassium hydrate, arsenic is oxidized, H is given off, and a mixture of potassium sr-senite and arsenide remains, which by greater heat is converted into arsenic, which volatilizes, and potassium arsenate, which remaixis. 

Chemical.—Its solutions are acid in reaction, and probably contain the true arsenious acid, HjAsOa. They arc neutralized by bases, with formation of arsenites. Solutions of sodium or potassium hydroxid dissolve it, with formation of the corresponding arsenite. It is readily reduced, with separation of As, when heated with hydrogen, carbon, or potassium cyanid, and at lower temperatures by more active reducing agents. Oxidizing agents, such as HlfOj, the hydrates of chlorin, chromic acid, convert it into arsenic pentoxid or arsenic acid. Its solution, acidulated with HCl and boiled in presence of copper, deposits on the metal a gray film, composed of an alloy of Cu and As. 

The insecticide calcium arsenate consists of the powdered salt (produced by neutralising arsenic acid with milk of lime) and hydrated lime. The mixture is dispersed in water before applying as a spray [30.1]. 

F. H. Storer obtained chromyl chloride. H. Moissan, 0. Popp, etc., found that it is soluble in sulphuric acid. W. Manchot and R. Kraus found that when warmed with sulphur dioxide, sulphur trioxide is formed and warm sulphurous acid is converted into sulphuric acid. C. W. Eliot and F. H. Storer, 0. Popp, etc., observed that chromic dioxide readily dissolves in dU. nitric acid the soln. is reddish-brown, and gives a dirty green precipitate with ammonia. W. Manchot and R. Kraus found that cone, nitric acid converts the dioxide into chromic acid. E. Hintz found that it is scarcely attacked by phosphorus pentachloride at 250°. A. Maus stated that a little arsenic acid converts the dioxide into chromic arsenate, which is soluble in an excess of arsenic acid. The dioxide is insoluble in ether, acetone, and other organic liquids and 0. Popp said that the dioxide dissolves with difficulty in acetic acid. M. Kriiger, W. Manchot and R. Kraus, etc., observed that boiling potassium or sodium hydroxide converts the dioxide into a soln. of alkali chromate, and a precipitate of hydrated chromic oxide. This simultaneous oxidation and reduction furnishes an illustration of the acidic and basic properties of chromium dioxide. A. Maus found that when digested with lead acetate in... 

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