Ammonium arsenites

Barium Metarsenite, Ba(As02)3, may be obtained by warming barium chloride with a solution of ammonium arsenite to which acetic acid has been added until arsenious acid is on the point of precipitation. The precipitate is then dried at 100° C.2 It is a white powder, easily soluble in water, but it can also be obtained as a gelatinous mass 3 when a mixture of barium chloride and potassium metarsenite in solution is left to stand for a few hours. On strongly heating it decomposes to form arsenate and free arsenic, but to a much less extent than is the case with the orthoarsenite.4... 

Calcium Pyroarsenite, Ca2As205, is a white powder obtained by slowly precipitating a solution of arsenious acid with excess of lime-water, or by adding calcium chloride or sulphate to aqueous ammonium arsenite, and heating the precipitate to 105° C.7 If the product is dried in the air at the ordinary temperature, the monohydrate is obtained. At red heat calcium arsenate is formed. The pyroarsenite is only slightly soluble in water, 100 parts dissolving 0-025 to 0-030 part of the salt. It is more soluble in the presence of alkali chlorides and some ammonium salts, such as the nitrate, sulphate, acetate and succinate.8 It also dissolves in dilute acids. 

Strontium Metarsenite, Sr(As02)2.4H20, may be obtained by the action of ammonium arsenite on a solution of a strontium salt.1 The precipitation is increased by the addition of alcohol, since the arsenite is fairly soluble in water. When dried at 100° C. it has the composition Sr(As02)2.3H20. At higher temperatures it decomposes to form strontium oxide, arsenious oxide and a little arsenic.2 Stavenhagen was unable to obtain the metarsenite in a pure state. 

Ammonium arsenites.—Between 70° and 80° C. ammonia reacts with a solution of arsenious oxide to form acicular crystals of ammonium meta-arsenite, NH AsOg.12 With concentrated ammonia arsenious oxide yields the crystalline ammonium pyroarsenite, (NH4)4As205, an unstable substance decomposed with evolution of ammonia on exposure to air.13... 

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. 

SODIUM AMMONIUM VANADATE SODIUM ARSAHILATE SODIUM ARSENATE SODIUM ARSENITE... 

Arsenites may also be determined by this procedure but must first be oxidised by treatment with nitric acid. Small amounts of antimony and tin do not interfere, but chromates, phosphates, molybdates, tungstates, and vanadates, which precipitate as the silver salts, should be absent. An excessive amount of ammonium salts has a solvent action on the silver arsenate. 

Wilson and Dickenson observed no exchange, over a period of three hours at 100 °C, between arsenate and arsenite ions in media ranging from aqueous acid to aqueous alkali. Martin et al have found similar results for the exchange between arsenate and thioarsenite ions in aqueous media. However, in liquid ammonia exchange occurred between ammonium arsenate and arsenic trisulphide. The isotopic method was used -... 

The most general method for the simultaneous analysis of oxyanions by gas chromatography is the formation of trimethylsilyl derivatives. Trimethylsilyl derivatives of silicate, carbonate, oxalate, borate, phosphite, phosphate, orthophosphate, arsenite, arsenate, sulfate and vanadate, usually as their ammonium salts, are readily prepared by reaction with BSTFA-TMCS (99 1). Fluoride can be derivatized in aqueous solution with triethylchlorosilane and the triethylfluorosilane formed extracted into an immiscible organic solvent for analysis by gas chromatography [685). 

The participation of cations in redox reactions of metal hexacyanoferrates provides a unique opportunity for the development of chemical sensors for non-electroactive ions. The development of sensors for thallium (Tl+) [15], cesium (Cs+) [34], and potassium (K+) [35, 36] pioneered analytical applications of metal hexacyanoferrates (Table 13.1). Later, a number of cationic analytes were enlarged, including ammonium (NH4+) [37], rubidium (Rb+) [38], and even other mono- and divalent cations [39], In most cases the electrochemical techniques used were potentiometry and amperometry either under constant potential or in cyclic voltammetric regime. More recently, sensors for silver [29] and arsenite [40] on the basis of transition metal hexacyanoferrates were proposed. An apparent list of sensors for non-electroactive ions is presented in Table 13.1. 

Other chemicals which inhibit milk lipase include hydrogen peroxide, animal cephalin, sodium arsenite, diisopropyl fluorophosphate, 2,4 din-itro-l-fluorobenzene, p-hydroxymercuribenzoate, potassium dichromate, lauryl dimethyl benzyl ammonium chloride, aureomycin, penicillin, streptomycin, and terramycin (Schwartz 1974). 

Arsenious sulphide is completely precipitated from a hot acid solution of an arsenite, and arsenic pentasulphide from one of an arsenate, by the addition of sodium thiosulphate, whilst both arsenites and arsenates are precipitated quantitatively as arsenious sulphide by ammonium thioacetate.6... 

H. Stamm also measured the solubilities of the salts of the alkalies in liquid ammonia —potassium hydroxide, nitrate, sulphate, chromate, oxalate, perchlorate, persulphate, chloride, bromide, iodide, carbonate, and chlorate rubidium chloride, bromide, and sulphate esesium chloride, iodide, carbonate, and sulphate lithium chloride and sulphate sodium phosphate, phosphite, hypophosphite, fluoride, chloride, iodide, bromate, perchlorate, periodate, hyponitrire, nitrite, nitrate, azide, dithionate, chromate, carbonate, oxalate, benzoate, phtnalate, isophthalate ammonium, chloride, chlorate, bromide, iodide, perchlorate, sulphate, sulphite, chromate, molybdate, nitrate, dithionate, thiosulphate, persulphate, thiocyanate, phosphate, phosphite, hypophosphite, arsenate, arsenite, amidosulphonate, ferrocyanide, carbonate, benzoate, methionate, phenylacetate, picrate, salicylate, phenylpropionate, benzoldisulphonate, benzolsulphonate, phthalate, trimesmate, mellitate, aliphatic dicarboxylates, tartrate, fumarate, and maleinate and phenol. 

Liu et al. [45] separated sub ng amounts of arsenite, monomethylarsenic and dimethylarsinic acids using dodeyldimethyl-ammonium bromide vesicles for liquid chromatography coupled to an inductively coupled plasma atomic emission spectrometer. 

The dissolution of sulphides in ammonium polysulphide can be regarded as the formation of thiosalts from anhydrous thioacids. Thus the dissolution of arsenic(III) sulphide (anhydrous thioacid) in ammonium sulphide (anhydrous thiobase), yields the formation of ammonium- and thio-arsenite ions (ammonium thioarsenite a thiosalt) ... 

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) ... 

Ammonium molybdate solution when the reagent and nitric acid are added in considerable excess to a solution of an arsenate, a yellow crystalline precipitate of ammonium arsenomolybdate, (NH4)3 AsMo, 2 40 is obtained on boiling (distinction from arsenites which give no precipitate, and from phosphates which yield a precipitate in the cold or upon gentle warming). The precipitate is insoluble in nitric acid, but dissolves in ammonia solution and in solutions of caustic alkalis. 

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