Magnesium arsenites

The bimolecular reduction of aromatic nitro compounds, depending on reaction conditions, may produce azoxy compounds, azo compounds, hydrazo compounds (1,2-diarylhydrazines), benzidines, or amines. Whereas the reduction with zinc and sodium hydroxide leads to azo compounds, zinc and acetic acid/acetic anhydride produces azoxy compounds. Other reducing agents suggested are stannous chloride, magnesium with anhydrous methanol, a sodium-lead alloy in ethanol, thallium in ethanol, and sodium arsenite. 

These compounds resemble in properties the arsenites of the metals, the characters of the iodides being suppressed. They are moderately stable in dry air but tend to become oxidised on keeping. With the exception of the magnesium compound they are slightly soluble in water, the solution apparently containing a complex salt with a simple metallic cation. When heated with water they undergo partial decomposition into the iodide and arsenious oxide. 

Colloidal saccharated iron is sometimes used in place of ferric hydroxide as an antidote in arsenical poisoning, but its adsorptive capacity depends on the alkalinity of the medium.4 Thus a commercial preparation containing 0-75 per cent, of sodium hydroxide was found to adsorb 12-57 per cent, of arsenious oxide (reckoned on the amount of iron present) addition of alkali increased the adsorption until, with 1-28 per cent, of sodium hydroxide present, there was a maximum adsorption of 27 per cent. The addition of acid correspondingly diminished the adsorption. A gel of ferric magnesium hydroxide, if prepared without boiling, also adsorbs arsenic from sodium arsenite solutions.5... 

A solution of normal sodium arsenate in aqueous ammonia and methyl or ethyl alcohol yields with lithium salts a pale pink precipitate which is quantitative and may be dried, ignited and weighed. An arsenite does not precipitate lithium. A mixture of the two acids may thus be quantitatively separated, the arsenate first by lithium in the presence of aqueous ammonia and alcohol, and the arsenite in the filtrate by precipitation with magnesium chloride solution.7... 

As Magnesium Pyroarsenate. The arsenic must be present as arsenate, so that any arsenite must first be oxidised, for example by... 

To a solution of 280 mg of 3a,lip,17,17a-tetrahydroxy-13a-(2-cyanoethyl)-D-homo-18-noretiocholan in 17 ml of methanol at room temperature contained in a 25 ml volumetric flask there was added 162 mg of sodium metaperiodate in 8 ml of water. A small amount of water was added to bring the volume to 25 ml. After 15 min an aliquot was withdrawn and added to a measured amount of sodium arsenite solution containing sodium bicarbonate and potassium iodide. After 10 min, the solution was titrated with standard iodine solution. The solution was diluted with water and extracted twice with ethyl acetate, each extract being washed in turn with sodium combined, dried over magnesium sulfate and concentrated to dryness under reduced pressure, yielding 265 mg of a colorless, amorphous product of 4b-methyl-ip-(2-formylethyl)-2p-formyl-2-(2-cyanoethyl)-4p,7a-dihydroxyperhydrophenanthrene. 

Magnesia mixture (see Section III.12, reaction 3) white, crystalline precipitate of magnesium ammonium arsenate Mg(NH4)As04.6HzO from neutral or ammoniacal solution (distinction from arsenite) ... 

Acidify the soda extract with dilute hydrochloric acid, pass in sulphur dioxide to reduce the arsenate to arsenite, boil off the excess sulphur dioxide (test with potassium dichromate paper), and pass hydrogen sulphide into the solution to precipitate the arsenic as arsenic(III) sulphide continue the passage of hydrogen sulphide until no more precipitate forms. Filter, boil off the hydrogen sulphide, and test the filtrate for phosphate by the ammonium molybdate test or with the magnesium nitrate reagent. 

Arsenite. (i) Action of H2S upon acid solution (III. 12, 1). (ii) Silver nitrate solution test (III. 12, 2), and absence of precipitate with magnesium nitrate reagent (III.12, 3) or on boiling with ammonium molybdate solution and nitric acid, (iii) Bettendorff s test (III.12, 6). 

Arsenite. Immediate precipitate of As2S3 in dilute HC1 solution (III.12, 1) and absence of precipitate with magnesium nitrate reagent (III.12, 3). 

It may be pointed out that if arsenite is also present it may be readily detected in the filtrate obtained by treating the original mixture of arsenate, phosphate, and arsenite with the magnesium nitrate reagent upon acidifying with 2m hydrochloric acid and passing hydrogen sulphide, an immediate yellow precipitate of arsenic(III) sulphide is produced. 

The carbonates, sulphates, and borates are decomposed. The sulphides of the alkalies and alkaline earths are decomposed while the sulphides of arsenic, antimony, molybdenum, zinc, cadmium, tin, iron, lead, copper, mercury, and palladium are not attacked. Cobalt sulphate is not attacked, while the sulphates of the alkalies and alkaline earths are attacked and dissolved. Alkali tungstates, ammonium arsenite and arsenate, copper arsenite, ammonium magnesium arsenate, ammonium molybdate and vanadate, potassium cyanide and ferrocyanide are decomposed. Paraffin is not attacked shellac, gum arabic, gum tragacanth, copal, etc., are decomposed. Celluloid is slowly attacked. Silk paper, gun cotton, gelatin, parchment are dissolved. M. Meslans 22 has studied the esterification of alcohol by hydrofluoric acid. 

LAPIS INFERNALIS (7761-88-8) A powerful oxidizer. Forms friction- and shock-sensitive compounds with many materials, including acetylene, anhydrous ammonia (produces compounds that are explosive when dry), 1,3-butadiyne, buten-3-yne, calcium carbide, dicopper acetylide. Contact with hydrogen peroxide causes violent decomposition to oxygen gas. Violent reaction with chlorine trifluoride, metal powders, nitrous acid, phosphonium iodide, red or yellow phosphorus, sulfur. Incompatible with acetylides, acrylonitrile, alcohols, alkalis, ammonium hydroxide, arsenic, arsenites, bromides, carbonates, carbon materials, chlorides, chlorosulfonic acid, cocaine chloride, hypophosphites, iodides, iodoform, magnesium, methyl acetylene, phosphates, phosphine, salts of antimony or iron, sodium salicylate, tannic acid, tartrates, thiocyanates. Attacks chemically active metals and some plastics, rubber, and coatings. 

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