tated salt then sublimes, and is converted into sulpho-arseniate Sect. 111. of mercury.* 29. Sulpho-arseniate of silver falls with a dark brown colour. At first it appears to dissolve in water, but gradually collects together, and appears black. When dried, it constitutes a black mass, whose powder is brown. The neutral and subsalt are quite alike. When distilled, it neither gives out sulphur nor sulphide of arsenic, and in a full red heat, melts into a splendid gray metallic bead, without giving out any volatile matter. This bead is soft, may be indented with the hammer, and cannot be pulverized.† 30. Sulpho-arseniate of gold is soluble with a reddish brown colour in water. The subsalt is thrown down of a dark brown colour, but is again dissolved when it is washed on the filter. When the solution is mixed with sulphate of iron, a yellowish brown substance falls, and the liquid becomes colourless. 31. Sulpho-arseniate of platinum forms, whether neutral or in the state of subsalt, a dark yellow solution, which becomes gradually dark brown without any precipitate falling. Sulphate of iron throws down a brown matter, so dark, that it appears black, and the liquid becomes colourless.§ 32. Sulpho-arseniate of antimony. pound, easily fusible. A bright yellow com 33. Sulpho-arseniate of chromium whether neutral or a subsalt has a muddy yellow, and when dry, an impure fine yellow colour.¶ 34. Sulpho-arseniate of molybdenum. A fine yellowish brown solution, which becomes darker, but lets fall no precipitate.** 35. Ammonia-sulpho-arseniate of sodium. The subsalt is obtained by mixing the two constituents that go to the formation of the double salt, and diluting the liquid with alcohol, and then agitating the whole. During the cooling, small foursided tables shoot upon the inside of the glass. When subsulpho-arseniate of sodium is dissolved in very little water, and sal ammoniac in the requisite quantity is added to the solution, the double salt gradually shoots into six-sided prisms, with two broad faces, having a slightly yellowish colour. The salt is not altered by exposure to the air. When distilled, sulphuret of ammonia and a little water passes over, and sulpho-arseniate of sodium remains. According to the analysis of Berzelius, this double salt is a compound of Berzelius, Kong. Vet. Acad. Handl. 1825, p. 280. + Ibid. p. 280. .. Ibid. Class VII. 1 atom subsesqui-sulpho-arseniate of sodium, 1 atom tris-sulpho-arseniate of ammonia. It is much more easily dissolved in water than the sodium salt alone.* 36. Ammonia-sulpho-arseniate of magnesium is formed when solutions of the two salts in alcohol are mixed. In a few minutes a subsalt falls in fine white crystalline needles. It is slowly decomposed by exposure to the air, to a neutral salt, and becomes yellow. It dissolves readily in water, and gives out sulphuret of ammonia if the liquid be heated. When left to spontaneous evaporation, it dries to a yellow mass, not crystallized, and soluble in water.† It is made by 37. Sodium-sulpho-arseniate of potassium. mixing together the two saline constituents. crystallize together in very regular, colourless, or slightly yellowish crystals, in shape quite similar to that of the two preceding double salts.‡ SECTION IV.—OF SULPHO-ARSENITES. These salts consist of compounds of orpiment, which might be called sesqui-sulphide of arsenic,§ and the alkaline sulphurets. They may be obtained in the same way as the sulphoarseniates, substituting for arsenic acid and sulphide of arsenic, arsenious acid and orpiment. They are formed exclusively by the dry way, and cannot be obtained by means of the alkaline sulphurets. Alkaline sulpho-hydrates dissolve orpiment only till the solution contain a bisulpho-arsenite. The sulphurets of barium, calcium, and magnesium, take up a very inconsiderable excess of orpiment. These salts (when the bases are colourless), whether neutral or in the state of subsalts, are colourless, and have only a slight tint of yellow. The salts with coloured bases, have, in general, the same colours as the sulpho-arseniates, their taste and smell are also similar. They are best obtained either in a solid form, or in a dilute solution. The subsalts may be kept better than the neutral or supersalts. When a solution of these salts is evaporated, it begins at a certain degree of concentration, to assume a brownish yellow colour. It then deposites a brown powder, which in Ibid. Hence * Berzelius, Kong. Vet. Acad. Handl. 1825, p. 282. + Ibid. $ This sulphide is analogous in its composition to arsenious acid. the reason for distinguishing this genus of salts by the name sulpho-arsenites. creases till the salt dries, when it is in a great measure decomposed into sulpho-arseniate and subsulpho-arsenite. Water dissolves only the first of these salts leaving the second, which, however, may be taken up by boiling water. Alcohol produces a similar decomposition. Orpiment dissolves easily in caustic potash or soda. The cold solution is nearly colourless; when boiled it assumes a dark brown colour, and at last deposites a dark brown powder, which, when dry, is almost black. The sulpho-arsenites with an alkaline basis, are not decomposed at a red heat in a retort. The others lose more or less of their orpiment. By alcohol they are decomposed in the same way as the sulpho-arseniates. The subsalts which are thrown down by alcohol, are obtained only when the solution is not fully saturated with orpiment. By acids they are altered in a way analogous to the sulpho-arseniates. Easily reducible oxygen bases or oxides form with them in the cold arsenites, and when boiled with them arseniates, while the reduced metal unites with the sulphur, producing a sulpho-arseniate. The solutions, when exposed to the air, undergo similar alterations with the sulpho-arseniates, but they deposite no sulphur. 1. Sulpho-arsenite of ammonia is obtained when orpiment is dissolved in sulpho-hydrate of ammonia, or in caustic ammonia. It is decomposed by spontaneous evaporation, and leaves a brown powder, consisting of a mixture of orpiment, with a lower degree of sulphide of arsenic. Orpiment is dissolved when boiled with carbonate of ammonia. When a solution of the neutral salt in water is mixed with alcohol, a white crystalline precipitate falls, which speedily becomes brown. But if the liquid be first mixed in an excess of sulpho-hydrate of ammonia, we obtain a milky liquid which afterwards becomes clear, while light feather-shaped crystals are deposited, constituting a subsalt composed of 1 atom sesqui-sulphide of arsenic 3 atoms sulphuret of ammonia 7.75 15.375 23.125 When collected on a filter, and washed with alcohol, they are white, but become yellow in the air while sulphuret of ammonia is evolved, and at last orpiment only remains.* Berzelius, Kong. Vet. Acad. Handl. 1825, p. 286. Sect. IV. } are obtained only in dilute 4. Sulpho-arsenite of lithium, solutions, or in an anhydrous form, by preparing them in the dry way. If orpiment be fused with carbonate of potash, and the excess of orpiment be driven off, we obtain bisulpho-arsenite of potas sium, from which water takes up a neutral sulpho-arsenite, and leaves a red undissolved matter consisting of sulphuret of potas sium saturated with orpiment, and a hyposulpho-arsenite of potassium. Caustic ammonia dissolves the first of these salts and leaves the second.* 5. Sulpho-arsenite of barium forms an almost colourless liquid, which dries to a gummy like substance, and assumes a fine reddish brown colour. It dissolves again completely in water without communicating colour. Alcohol throws down from the solution a subsalt in crystalline plates. It is formed also when orpiment is digested with an excess of sulphuret of barium. It dissolves with difficulty in water, and when evaporated in the open air deposites fine white flocks of a subsalt mixed with minute cry-tals of sulphate of barytes.† 6. Sulpho-arsenite of calcium is formed by macerating orpiment with hydrate of lime and water, the arsenite of lime which is formed at the same time, remaining undissolved. The solution is colourless, and when left to spontaneous evaporation deposites fine feather-shaped crystals of a subsalt, mixed with which occurs the neutral salt in the state of a brown matter, not crystallized. If the neutral salt be mixed with more orpiment, it takes up an additional portion and becomes yellow, but soon begins to deposite a brown powder. If it be now left to spontaneous evaporation, it becomes light brownish red. and leaves, when dissolved,subsulpho-arsenite of calcium behind. If alcohol be mixed with a filtered solution of a salt with excess of sulphuret of calcium we obtain a white crystalline precipitate composed, according to the analysis of Berzelius, of Orpiment Sulphuret of calcium Berzelius, Kong. Vet. Acad. Handl. 1825, p. 285. 33.55 29.80 36.65 100.00 † Ibid. p. 247 7. Sulpho-arsenite of magnesium is easily soluble in water. When the solution is evaporated it becomes light brown, assumes the form of a clammy mass, which at last dries, and is no farther altered in the air. Every time it is dissolved and evaporated it leaves a little brown hyposulpho-arsenite. It dissolves completely and easily in alcohol. If a concentrated aqueous solution be left in the temperature of 23° it deposites colourless needles of hyposulpho-arsenite, and a dark reddish brown mass of sulpho-arsenite of magnesium. 8. Sulpho-arsenite of glucinum gives a light yellow precipitate without the smell of sulphide of hydrogen. The supernatant liquid is yellow, a proof that the precipitate is soluble in it. The precipitate retains its colour when dried. Caustic ammonia dissolves the orpiment and leaves the regenerated earth.† } exhibit the same pro- 9. Sulpho-arsenite of aluminum 10. Sulpho-arsenite of yttrium 11. Sulpho-arsenite of cerium gives a very fine orange precipitate like chromate of lead. The supernatant liquid is yellow. The colour becomes still finer when the precipitate is dried. It fuses in an incipient red heat and becomes translucent. After this it gives out a portion of orpiment, but continues in fusion and retains its transparency. The fused mass when roasted in the open air is easily changed into a sulphate.§ 12. Sulpho-arsenite of zirconium forms an orange yellow precipitate which blackens when dried, and is not decomposed by acids. It is slightly soluble in water.|| 13. Sulpho-arsenite of iron gives a dark brown precipitate, almost black, which dissolves with a brown colour in an excess of the precipitating medium. When dried it becomes grayish brown, and when pulverized gives a dark brownish powder, consisting of oxide of iron united to sulpho-arsenite of bisulphuret of iron. When distilled it gives off orpiment and sulphurous acid, and leaves sulphate of iron.¶ |