However, it appears from the experiments of Ittner, that hydro-cyanic acid and alumina may be combined by double decomposition. 8. Cyanodide of iron. This salt was obtained by Berzelius by heating prussiate of ammonia in close vessels till all the hydro-cyanate of ammonia was disengaged. It is a grayish yellow matter, which may be preserved undecomposed. When exposed to a stronger heat it becomes brown, giving out azotic gas. When still farther heated it becomes black bicarburet of iron. At a red heat it takes fire and burns like tinder, leaving peroxide of iron, which weighs just as much as the bicarburet.* It is believed at present, that there exists also a sesquicyanodide of iron analogous to peroxide and perchloride of iron, but it has not yet been obtained except in combination. 9. Cyanodide of manganese. It is precipitated when a solution of cyanodide of potassium is mixed with a protosalt of manganese. The stronger acids decompose it. Water does not dissolve it, but it is soluble in the alkaline prussiates. 10. Cyanodide of nickel. Hydro-cyanic acid precipitates acetate of nickel completely, and sulphate and nitrate of nickel partially. The precipitate is light apple green, but when dried it becomes leek green. When heated it gives out water, and a light brown matter remains, which is a cyanodide of nickel. When strongly heated it gives out cyanogen and azotic gas, and leaves a mixture of metallic nickel and charcoal.+ 11. Cyanodide of cobalt. According to Scheele, carbonate of cobalt dissolves with effervescence in liquid hydro-cyanie acid. The salt precipitates when solutions of cyanodide of potassium and a cobalt salt are mixed together. It is a brownish white powder, insoluble in water and in acids. Sect. I. 5 Hence the reason why the weight continues unaltered. + Wöhler. Class VI. 12. Cyanodide of zinc. According to Scheele, when hydrocyanate of lime is mixed with sulphate of zinc a white precipitate falls, neither soluble in water nor in an excess of hydro-cyanate of lime. But the stronger acids dissolve it while hydro-cyanic acid is disengaged. When this salt is distiled carbonate of zinc remains behind.* 13. Cyanodide of lead. When acetate of lead and cyanodide of potassium are mixed a white heavy precipitate falls, which is not soluble in water, but dissolves in the stronger acids with the evolution of hydro-cyanic acid. 14. Cyanodide of tin. This salt has not yet been examined. It has been ascertained that none of the salts of tin are precipitated by cyanodide of potassium. 15. Cyanodide of copper. Aqueous hydro-eyanic acid when digested over copper with the assistance of heat, occasions an effervescence, and forms a brownish yellow matter. Cyanodide of potassium or calcium when not added in excess throw down from all the solutions of oxide of copper a similar precipitate. The salt, if left in the liquid, undergoes decomposition, while cyanogen is evolved. 16. Dicyanodide of copper. When hydro-cyanic acid, or cyanodide of potassium, is mixed with dichloride of copper white cheesy precipitate falls. When this precipitate is gently heated it melts into a brownish matter. If the heat be continued there comes over first a liquid which reddens litmus paper, then ammonia is disengaged, and a brownish residue remains behind. The salt dissolves in liquid ammonia into a colourless solution, in concentrated muriatic acid it dissolves with a yellow colour. a 17. Cyanodide of mercury. This salt in a crystallized state seems to have been first obtained by Berthollet, but it was Gay-Lussac that first pointed out its real nature. It is easily obtained by digesting a mixture of red oxide of mercury and prussian blue in a sufficient quantity of water. If the two substances be used in the requisite proportions, the prussian blue loses its blue colour, and the oxide of mercury dissolves. When the filtered solution is concentrated the cyanodide of mercury is deposited in large white translucent crystals. The primary form of these crystals is a right square prism. The base of the prism is frequently replaced by two faces, rising from two opposite angles of the prism and meeting at an angle * Berzelius. of 114°. * It has a bitter, and, at the same time, a mercurial and very disagreeable taste. It dissolves readily in water and in weak alcohol. Its constituents, as determined by the analysis of Gay-Lussac, are When heated it blackens, gives out cyanogen gas, while mercury is disengaged. There is formed at the same time a very light black charry matter, which Mr. Johnston assures us is composed of the very same constituents as cyanogen, namely, 1 atom azote, and 2 atoms carbon; but the properties of the substance are scarcely compatible with that opinion. It has been generally considered as a compound of 1 atom azote, and 3 atoms carbon; but I am not aware that these constituents have been established by satisfactory experiments. When this salt is distilled while moist, there are disengaged carbonic acid, ammonia, hydrocyanic acid, and mercury. When mixed with sulphuric acid, it forms a gelatinous mass, having a weak odour of hydro-cyanic acid. When there is an excess of sulphuric acid, it becomes yellow, while hydro-cyanic acid is disengaged. This salt is not decomposed by aqueous solutions of the oxygen acids, not even by nitric acid, nor by the aqueous solutions of alkalies. 18. Subcyanodide of mercury. This compound was obtained by Grouvelle, who boiled a solution of cyanodide of mercury on red oxide of mercury, till the liquid refused to take up any more. From the quantity dissolved, he has drawn as a conclusion, that the new compound is formed of 3 atoms cyanodide of mercury 2 atoms red oxide of mercury When the solution is evaporated, it yields small, four-sided, oblique needles. 19. Cyanodide of silver. It is obtained when nitrate of silver is mixed with hydro-cyanic acid, or cyanodide of potassium. It constitutes a white curdy precipitate. When heated in a * Brooke, Annals of Philosophy (2d series), vi. 42. † Ann. de Chim. et de Phys. xvii. 54. Sect. I. Class VI. close vessel, it gives out a portion of cyanogen, and melts into a mass, which has a reddish brown colour while hot, but becomes gray when cold. When heated in the open air. the whole cyanogen is disengaged. 20. Cyanodide of gold. Hydro-cyanate of lime or potash throws down muriate of gold white. When heated, the salt becomes yellow. When heated still more strongly, water and gaseous matter are given off, and there remains a mixture of gold and charcoal. This salt is soluble in liquid ammonia. 21. Cyanodide of platinum. Hydro-cyanic acid has no action on oxide of platinum, and hydro-cyanate of lime does not produce a precipitate in the solutions of platinum. 22. Cyanodide of palladium. A light yellow white powder. When prepared from nitrate of palladium, it detonates like gun-powder, with a weak light, as Wollaston ascertained. SECTION II.- -OF CYANATES.† To the acid described in page 225 of this volume under the name of cyanous acid, Wöhler, who discovered it, gave at first the name of cyanic acid. This name was changed into cyanous acid, in consequence of the discovery, by Serullas, of another acid, which he considered as cyanogen combined with twice as much oxygen as exists in Wöhler's acid. But it has been since ascertained by Wöhler and Liebig, that the acid of Serullas contains also hydrogen. Hence its constitution is quite different from that of Wöhler's acid. It will be expedient, in consequence of this discovery, to restore the name cyanic to the acid of Wöhler, and to distinguish the acid of Serullas by a new appellation. 1. Cyanate of potash. I have given the process for obtaining this salt in page 226 of this volume. It is composed of small plates or needles, and has some resemblance to chlorate of potash. It has the taste of saltpetre, is not altered by exposure to the air, and in a red heat it fuses and is decomposed. When the solution of it in water is boiled, the salt is completely changed into carbonate of potash, while ammonia is disengaged. The same change takes place gradually even without the application of heat. When hydrogen gas is passed * Scheele. + This acid and its salts ought to find its place among the oxygen acids and their salts. But I have placed them here provisionally, because I consider many points respecting the compounds of cyanogen as not yet fully established. over the ignited salt, it deprives both of its constituents of their oxygen, and a cyanodide of potassium is formed. But the water produced by this decomposition, decomposes another portion of the salt into carbonate of potash and ammonia. Potassium dissolves in this salt with tranquillity. The solution consists of a mixture of cyanodide of potassium and potash. Iron filings heated to redness in it, form cyanodide of potassium, ferro-cyanodide of potassium, and protoxide of iron. When sulphur is melted with it, the products are sulphocyanodide of potassium, sulphuret of potassium, and sulphate of potash. Sulphuretted hydrogen gas changes the fused salt into a yellow mass of sulphuret of potassium, and sulpho-cyanodide of potassium, while at the same time some hydro-sulphuret of ammonia sublimes in consequence of the water formed during the action. When heated with concentrated sulphuric acid, carbonic acid is evolved, and sulphates of potash and of ammonia are formed. Diluted sulphuric acid causes the evolution of some cyanic acid, which escapes with the carbonic acid. This salt is readily dissolved in water. It is soluble in hot alcohol of the specific gravity 0-832, but not in absolute alcohol. Its constituents, according to the analysis of Wöhler, are Sect. II. 2. Cyanate of soda. This salt, according to Wöhler, is capable of crystallizing. 3. Cyanate of barytes. The method of forming this salt has been described in page 225 of this volume. It crystallizes in transparent silky needles. When ignited with sulphur, there are formed hydro-sulphuret of ammonia, sulphate of barytes, sulphuret of barium, and sulpho-cyanodide of barium. When this salt is dissolved in water, and the solution evaporated, it is decomposed into carbonate of barytes, and tercarburet of azote. 4. Cyanate of lime. It may be prepared by the same process as the preceding salt, by passing the vapour from heated urate of mercury through lime water. It does not crystallize.+ 5. Cyanate of iron. This salt may be obtained by decom |