27. Ferro-cyanodide of molybdenum. Prussiate of potash, Sect. VII. when dropt into salts of protoxide of molybdenum, throws down a dark brown precipitate, which is soluble in an excess of prussiate of potash and also in liquid ammonia with a dark brown colour. A brown powder, similar in appearance, is thrown down by prussiate of potash from the salts of deutoxide of molybdenum, but it is not soluble in an excess of prussiate of potash. When prussiate of potash is mixed with a solution of molybdic acid in a stronger acid, a reddish brown precipitate falls, paler than the two preceding ones. It dissolves in an excess of prussiate of potash with a dark reddish brown colour. In liquid ammonia it dissolves, and the solution is almost colourless.* 28. Ferro-cyanodide of titanium. Prussiate of potash throws down the salts of titanium of a yellowish brown colour. 29. Ferro-cyanodide of columbium. When prussiate of potash is mixed with a solution of muriate of columbium a deep yellow precipitate falls, which, after being washed and dried, becomes dark brown. It is not altered by exposure to the air or by the action of boiling water. Iron is not the only metal which combines with potassium into a double cyanodide. Probably all the other metals are capable of replacing iron, and of making with potassium a double cyanodide, which, like prussiate of potash, is capable of entering into combination with other cyanodides, and of forming new classes of double cyanodides. The following 8 of these salts have been already formed. 1. Manganese-cyanodide of potassium, 8. Tellurium-cyanodide of potassium. These salts are some of them colourless, and some of them yellow. They usually crystallize, and the crystal is most commonly an octahedron, or a rhombohedron. Each of these • Berzelius. Class VII. Salts might be used like common prussiate of potash, to throw down the different metallic salts, and the double cyanodides formed, are distinguished by a different set of colours, and different properties, from those that have been described in this section; but they have not been examined sufficiently in detail to enable us to describe them here. But it must be obvious at a glance, how very much these different genera of double eyanodides will hereafter increase the number of cyanogen salts. CLASS VII. OF SULPHUR ACID SALTS, The investigation of this class of salts was begun by Berthollet in his paper on sulphuretted hydrogen, published in the 25th volume of the Annales de Chimie. Several additional facts were afterwards added by Vauquelin. But for the generalization of the subject, and for our knowledge of all the genera of sulphur acid salts, except the first, we are indebted to Berzelius. He first pointed out the fact, that sulphur acids, and sulphur bases exist, capable of combining with each other." He afterwards published a numerous and elaborate set of experiments on the sulphur salts, in which he details the properties of nine different genera of these salts, and gives a notice of three other genera. I have already, in page 256 of this volume, mentioned, that I proposed to distinguish those combinations of sulphur and a base, which possess acid properties, by the name of sulphides, and those that possess alkaline proNomencla. perties, by the name of sulphurets. Thus, sulphide of hydro ture. gen (the body hitherto distinguished by the terms, sulphuretted hydrogen, hydro-sulphuric acid, &c.) is an acid compound of sulphur and hydrogen; while sulphuret of copper is an alkaline compound of sulphur and copper. Sulphur acids, and sulphur bases, are capable of uniting without decomposition, and of forming various genera of salts, many of which are soluble in water, and are capable of crystallizing. In naming these salts, it is obvious that we must abbreviate the name both of the acid and base, otherwise the terms would be too cumbersome *Kong. Vet. Acad. Handl. 1821, p. 145. + Ibid. 1825, p. 232, and 1826, p. 53. for use, and would be altogether unsuitable to the idiom of the English language. But we may apply the method which has been hitherto employed for naming the oxygen acid salts. To the base of each sulphur acid terminating in ate, I shall prefix the syllables sulpho, which will be a sufficient indication that the salt is a sulphur salt. Thus, a sulpho-hydrate is a sulphur salt, whose acid is sulphide of hydrogen. The base of a sulphur salt being always a sulphuret, or an alkaline base united to sulphur, the nature of the salt will always be sufficiently understood, if we simply add the name of the alkaline base without noticing the sulphur, which is constantly present. Thus, sulpho-hydrate of zinc will indicate that the salt is a compound of sulphide of hydrogen and sulphuret of zinc. Should it be hereafter discovered, that various sulphurets, having the same alkaline base, are capable of uniting with the same sulphur acid, it will become necessary to distinguish the various sulphurets which enter into the combination, just as it is necessary to distinguish the various oxides which unite with the same oxygen acid; and a mode similar to that used for distinguishing these different oxides in the preceding part of this work, might easily be applied to the sulphur bases. In the present state of our knowledge, however, this is unne cessary. Sect. I. SECTION 1.—OF SULPHO-HYDRATES. When sulphide of hydrogen is made to pass into a solution of any oxidized body, for example into a solution of potash or soda, the oxide is always decomposed by the union of its oxygen with the hydrogen of the sulphide, while the base of the oxide unites to the sulphur of the sulphide, and forms a sulphuret of potassium, of sodium, &c. With this sulphuret a new dose of sulphide of hydrogen is capable of entering into combination, and of forming a sulphur salt. It is in this way that sulpho-hydrates are usually formed. Several of them have been long known under the names of hydro-sulphurets, hydrosulphates, hydro-thionates, &c. They are occasionally used as reagents, and are very useful in chemical analyses. 1. Sulpho-hydrate of ammonia. This salt may be obtained by passing a current of sulphide of hydrogen gas and another of ammoniacal gas into a bottle surrounded with ice. It crystallizes in needles, and is transparent and colourless. It is very volatile, and, when kept in a bottle, sublimes gradually to the top of the vessel, where it crystallizes in long transparent Class VII. plates. By this spontaneous volatilization, it is easily freed from any impurities with which it may be mixed. When exposed to the air, it speedily becomes yellow.* This salt may be obtained also, according to Berzelius, by distilling sulphuret of potassium mixed with an excess of sal ammoniae and water. Sulpho-hydrate of ammonia has not been hitherto subjected to a rigid analysis. There are probably two, if not more salts, distinguished by the proportions of the constituents. Whether the ammonia be combined with sulphur is not so clear. As ammonia contains no oxygen, it cannot decompose sulphide of hydrogen. I believe, in general sulpho-hydrate of ammonia contains two atoms of base united to one of sulphide, though the neutral combination is also possible. When equal parts of lime, sal ammoniac, and sulphur, are distilled in a retort, a yellow liquid is obtained, usually distinguished by the name of fuming liquor of Boyle, because first prepared by that philosopher. This liquid constantly emits white fumes, and has a strong ammoniacal and fetid odour. Berthollet ascertained that it owed its property of emitting fumes to a quantity of uncombined alkali. It consists chiefly of sulpho-hydrate of ammonia holding an excess of sulphur. This liquid gradually loses the property of fuming, and deposites likewise its excess of sulphur. It is then a sulpho-hydrate of ammonia nearly pure. 2. Sulpho-hydrate of potassium. This salt may be obtained by passing a current of sulphide of hydrogen over carbonate of potash heated to obscure redness, till all evolution of water and carbonic acid is at an end. It is a foliated substance of a lemon yellow colour, which deliquesces speedily in the air, and dissolves readily in water, and when the solution is mixed with the stronger acids, sulphide of hydrogen is given out abundantly, without the precipitation of any sulphur. By evaporation it yields crystals, which are transparent and colourless, and crys tallizes in large prismatic crystals, not unlike sulphate of soda. They are usually four-sided, and terminated by four-sided pyramids. Sometimes both the prisms and terminating pyramids are six-sided. Its taste is alkaline and extremely bitter. When exposed to the air, it soon deliquesces into a liquid of a syrupy consistence, tinging green all bodies with which it happens to be in contact. But this colour is not permanent. unless some metallic body happens to be in contact. *Thenard, Ann, de Chim. lxxxiii 134. The crystals have no smell; but when they have deliquesced they emit a fetid odour. They dissolve both in water and alcohol; and during the solution the temperature of the liquid sinks considerably.* The constituents of this salt (abstracting the water of crystallization, which is still undetermined), are 1 atom sulphide of hydrogen 2.125 7 9.125 3. Sulpho-hydrate of sodium. This salt may be formed by exposing sodium in an atmosphere of sulphide of hydrogen. It first combines with an atom of sulphur, by decomposing the sulphide and the sulphuret thus formed, absorbs an additional dose of sulphide, and is converted into sulpho-hydrate. We may form it also in the same way as was described for forming the last salt. The aqueous solution crystallizes. I have given an account of this salt in the first volume of this work, page 268; though the view there given of its constitution is probably not quite accurate. Its crystals are regular octahedrons. The taste is very hot, bitter, and sulphureous. It is not sensibly altered by exposure to the air for 24 hours, but it slowly deliquesces into a brown liquid. Its alkaline properties are as powerful as those of a strong caustic potash ley. When heated it undergoes the watery fusion, then becomes solid, and finally catches fire and burns like tinder for a long time, with a very low yellow coloured flame. Its constituents are doubtless 1 atom sulphide of hydrogen 1 atom sulphuret of sodium 2.125 7.875 Sect. I. 15't 4. Sulpho-hydrate of lithium. To obtain this salt sulphate of lithia may be mixed with charcoal and ignited in a porcelain crucible. The residual matter is to be thrown into water, filtered and saturated with sulphide of hydrogen. A colourless solution is obtained. When concentrated in a retort filled * Vauquelin, Ann. de Chim, xlii. 40. + Phil. Trans. 1827, p. 167. I suppose my analysis to have been erro. neous by 0.125 or an atom of hydrogen, which being under one per cent. might have been easily committed. |