Silver arsenates

Silver compounds having anions that are inherently toxic, eg, silver arsenate and silver cyanide, can cause adverse health effects. The reported rat oral LD values for silver nitrate, silver arsenate [13510-44-6] and silver cyanide are 500—800 (29), 200—400 (29), and 123 mg/kg (30), respectively. Silver compounds or complexes ia which the silver ion is not biologically available, eg, silver sulfide and silver thiosulfate complexes, are considered to be without adverse health effects and essentially nontoxic. 

Discussion. Arsenates in solution are precipitated as silver arsenate, Ag3 As04, by the addition of neutral silver nitrate solution the solution must be neutral, or if slightly acid, an excess of sodium acetate must be present to reduce the acidity if strongly acid, most of the acid should be neutralised by aqueous sodium hydroxide. The silver arsenate is dissolved in dilute nitric acid, and the silver titrated with standard thiocyanate solution. The silver arsenate has nearly six times the weight of the arsenic, hence quite small amounts of arsenic may be determined by this procedure. 

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. 

Apparent indicator constant 264, 267 Apparent stability constant 59 Aqua regia 111 Arc alternating current, 764 direct current, 763, 771 sensitivities of elements, (T), 766 Aromatic hydrocarbons analysis of binary mixtures, 715 Arsenates, D. of (ti) 357 Arsenic, D. of as silver arsenate, (ti) 357 as trisulphide, (g) 448 by iodine, (am) 634, (ti) 397 by molybdenum blue method, (s) 681 by potassium bromate, (ti) 406 by potassium iodate, (ti) 401 in presence of antimony, (s) 724 Arsenic(III) oxide as primary standard, 261... 

Losses of Silver, Arsenic, Cadmium, Selenium, and Zinc from Seawater by Sorption... 

Babbit metal. A soft alloy of metals such as tin, silver, arsenic, and cadmium combined with a lead base. It can be cast or used as a coating on steel bearings to form an oil-hke coating that reduces friction. Used to make oil-less bearings. 

Heavy metals such as copper, zinc, lead, nickel, silver, arsenic, selenium, cadmium and chromium may originate from many sources within a rehnery and may, in specihc cases, require end-of-pipe treatment. Some agencies have set discharge limits that are beyond the capability of common metals removal processes such as lime precipitahon and clarihcation to achieve. Other treatment processes such as iron coprecipitation and adsorption, ion exchange, and reverse osmosis may be required to achieve these low effluent concentrations [52]. 

OxideofOoba.lt, the ores of which, after grinding and roasting, to drive off as much as possible the excess of arsenic and sulphur, are dissolved in hydrochloric add, sometimes with the addition of a small quantity of nitric acid. The copper, lead, silver, arsenic, antimony, el cetera, are precipitated by sulphide of hydrogen, and to the filtered solution carbonate of lime is added in (he form of chalk, by which all the iron, alumina, and a trace ot cobalt are thrown down, the nickel and cobalt remaining in solution. To this solution which must ho hot and neutral, a solutien of bleaching powder is added in sufficient quantity to precipitate the cobalt, and the menstruum is then well boiled to remove the chlorine as fast as possible. The oxide of nickel is afterwards precipitated from the filtrate by the addition of hydrate of lime, and ebullition. 

Baxter and Coffin,1 in 1909, also heated silver arsenate in hydrogen chloride. Samples of different origin were used, with slightly different results. They also dissolved the arsenate in nitric acid and precipitated the silver as chloride or bromide. The following mean values were obtained ... 

Orange-red crystals of dimercurous silver arsenate, Hg2AgAs04, have been obtained by adding hydrogen peroxide solution, free from chlorides, to a solution of silver nitrate, mercurous nitrate and potassium... 

Sodium dihydrogen arsenate or arsenic acid does not precipitate mercuric chloride solution, but the latter reacts with normal silver arsenate to form normal mercuric arsenate and silver chloride. Yellow precipitates containing normal mercuric arsenate, mercuric chloride and mercuric oxide are thrown down from mercuric chloride solution by a solution of sodium monohydrogen arsenate. 

Silver Arsenates.—Silver nitrate reacts with solutions of arsenic acid or arsenates, giving a chocolate-coloured precipitate of silver orthoarsenate, Ag3As04, containing a small proportion of silver nitrate, possibly in solid solution.1 The adsorption of silver nitrate is prevented by the presence of ammonium nitrate. The precipitation is incomplete in acid solution.2 The orthoarsenate cannot be completely dried except by fusion. 

PROUSTITE. This ruby-silver mineral crystallizes in the hexagonal system its name is a product of its scarlet-to-vermilion color when first mined It is a silver arsenic sulfide. AgjAsS, of adamantine luster Hardness of 2-2,5 specific gravity of 5.55-5.64. Usual crystal habit is prismatic to rhombohedral more commonly occurs massive. Conchoidal to uneven fracture transparent to translucent color, scarlet to vermilion red. Light sensitive must be kept in dark environment to maintain its primary character. A product of low-tcmpcraturc formation in most silver deposits. Notable world occurrences include the Czech Republic and Slovakia, Saxony, Chile and Mexico. Found in minor quantities in the United States the most exceptional occurrence at the Poorman Mine, Silver City District. Idaho where a crystalline mass of some 500 pounds (227 kilograms) was recovered m 1865, It was named for the famous French chemist, Louis Joseph Proust. 

Figure 3 compares the results obtained for the Matisse bronze samples with LA-ICP-MS and ICP-MS for six elements zinc, tin, lead, arsenic, bismuth and silver. The best correlations between ICP-MS and LA-ICP-MS occur for silver, arsenic and tin. For zinc, lead and bismuth, the results by ICP-MS and LA-ICP-MS concur quite well for some samples. For the other samples, the values are either over or underestimated. Immiscibility of lead in copper, even at low concentrations, could explain the non-agreement for some samples between the ICP-MS and the LA-ICP-MS results (13). However, zinc and bismuth are miscible in copper at the concentrations encountered in the Matisse bronze sculptures. 

By treating the spot with hot nitric acid, evaporating to dryness on a water-bath, dissolving the residue in two drops of water and adding ammoniacal silver nitrate solution (2 or 3 drops) in presence of arsenic a brick-red precipitate of silver arsenate is formed. 

Brownish red precipitate of silver arsenate from neutral solutions Yellow precipitate (in presence of excess reagent) of ammonium arsenomolybdate (NH4)3AsMo1204 Iodine formation... 

Massee, R., and Maessen, P. J. M. J. (1981). Losses of silver, arsenic, cadmium, selenium, and zinc traces from distilled water and artificial sea-water by sorption on various container surface. Anal. Chim. Acta 127, 206—210. 

Silver nitrate solution brownish-red precipitate of silver arsenate Ag3As04 from neutral solutions (distinction from arsenite and phosphate which yield yellow precipitates), soluble in acids and in ammonia solution but insoluble in acetic acid. 

Upon treating the white precipitate with silver nitrate solution containing a few drops of acetic acid, red silver arsenate is formed (distinction from phosphate) ... 

If phosphate has been detected previously (e.g. in the cation analysis), a qualitative test for arsenate may be made as follows. Pour 1 ml AgN03 solution, to which 2 drops of dilute acetic acid have been added, over the white precipitate. A brownish-red colouration of the precipitate confirms the presence of arsenate. The acetic acid is added to increase the solubility of the magnesium salt and thus facilitate the conversion of magnesium ammonium arsenate to the characteristic silver arsenate. 

If the white precipitate of magnesium ammonium phosphate is washed with a little water, and then treated on the filter paper with a little silver nitrate solution containing a few drops of dilute acetic acid, a yellow colouration, due to silver phosphate, is obtained. However, a similar reaction with the white precipitate produced by the magnesium nitrate reagent with a mixture of phosphate and arsenate yields a brownish-red colouration on the white precipitate this is due to silver arsenate. 

Cupric arsenate, Cu3(As04)2.—The arsenate occurs as pentahydrate under the name trichalcite. The tetrdhydrate is produced by heating cupric nitrate with calcium arsenate, or copper with a solution of arsenic acid,1 and also by the interaction of cupric chloride and silver arsenate.2 Concentration at 70° C. of a solution of cupric carbonate in excess of arsenic acid yields pale-blue leaflets of the formula CuHAsO 4,H20.3 Other acidic salts,4 and also basic salts,5 are known. 

Silver arsenate, Ag3As04.—Silver nitrate reacts with solutions of arsenic acid and arsenates, giving a chocolate-coloured precipitate of silver arsenate containing a small proportion of silver nitrate, possibly... 

---