Cyanides of the Metals. 65 



and metallic taste. They are perfectly colourless and trans- 

 parent, but seem opake from being composed of numerous 

 small crystals. They are soluble in four times their weight 

 of cold water, and in less than their own weight of boiling 

 water, in the proportion of 5 to 4. They are very sparingly 

 dissolved by alcohol, and their solubility is not increased by 

 boiling. When alcohol is added to a warm saturated solu- 

 tion of the crystals, the salt falls in fine white brilliant shining 

 scales, which are quite opake. Their solution does not stain 

 the hands by the action of light, neither is the solution affected 

 by exposure to light. When nitric, muriatic, or sulphuric 

 acid is poured over the crystals, they are not affected at first, 

 but by standing some time they are quite decomposed, and 

 cyanide of gold results. The cyanide of gold occasionally 

 precipitates in minute shining crystals from the nitric solution. 

 Their solution is not immediately effected in the cold by these 

 acids, but a boiling temperature decomposes them, the yellow 

 cyanide of gold precipitating. Tartaric, oxalic and acetic 

 acids effect the same decomposition when boiled. The nitric, 

 muriatic and sulphuric acids added to a cold saturated solu- 

 tion precipitate the salt undecomposed. The following me- 

 tallic solutions were added to a solution of the salt, and the 

 results were as follows : — 



Nitrate of copper . . a white precipitate of the mixed cyanides. 

 Sulphate of zinc .. . 

 Nitrate of silver .. . ... ... 



Nitrate of mercury . a yellow-white precipitate ... 



Acetate of lead ... a white precipitate 



Protosulph. of iron . a white precipitate of the mixed cyanides, 

 which changes to a purplish-blue on 

 the addition of nitric acid. 

 Muriate of man- . small crystals appear on the sides of the 



ganese glass on standing. 



Muriate of tin .... a slight opacity, increasing to a precipi- 

 tate on standing. 

 When ex})osed to a red heat with their own weight of car- 

 bonate of potash, the whole of the gold is obtained in the me- 

 tallic state as a bright button. The carefully dried salt was 

 treated in this way and the following results obtained : — 



16. A salt prepared with oxide of gold and cyanide of po- 

 tassium yielded the following results : — 



7 grs. yielded ^-G? gold = 66*71 per cent. 

 .5 grs. ... 3-33 ... = Q6'Q6 

 10 grs. ... 6-63 ... = 66-30 ... 



The salt prepared by the battery process was also examined : 

 it gave the following results : — 



Phil. Mag. S. 3. Vol. 25. No. 163. July 1844. F 



