On the Re-action ofSulphwet of Carbon^ S^-c. 151 



brown with salts of copper ; yellow with corrosive sublimate. All 

 these precipitates change gradually; that of lead becomes black, 

 and diminishes in bulk to a powder, which has the properties of 

 sulphuret of lead, and at the same time sulphuret of carbon sepa- 

 rates. The change is produced without access of air. When the 

 precipitate is rapidly dried by the air-pump, and then heated in a 

 bent tube, sulphuret of carbon rises leaving sulphuret of lead. 

 Hence it may be concluded that these metallic precipitates are 

 formed of metallic sulphurets and sulphuret of carbon; from 

 whence it follows that the reddening salt may be considered as a 

 compound of ammonia, and a double sulphuret of hydrogen and 

 carbon. It contains no sulphuretted cyanogen, for when precipi- 

 tated by nitrate of lead the remaining solution does not, when 

 tested by a per-salt of iron, indicate sulphocyanic acid; but, if the 

 salt of ammonia be previously heated with solution of potash, 

 abundance of sulphocyanic acid is formed. 



9. The double sulphuret may be separated from the reddening 

 salt, by throwing a mass of the latter into sulphuric or muriatic 

 acid, but little diluted, and ihen adding a sufficient quantity of 

 water. The double sulphuret is obtained, with scarcely any libera- 

 tion of sulphuretted hydrogen, as a reddish-brown oil heavier than 

 the fluid about it ; but the process does not always easily succeed. 

 This substance differs in its odour from sulphuretted hydrogen : it 

 cannot be preserved long, so that its examination when pure is 

 difficult, but when separated from the acid about it as much as 

 possible, it may be seen that in contact with carbonate of baryta 

 under water there was an immediate effervescence ; a soluble sub- 

 stance is obtained, which M. Zeise considers as a compound of 

 sulphuret of barium and sulphuret of carbon, and which is very 

 alkaline, although carbonate of baryta was used. 



10. The reddening salt, confined with alcohol in a close vessel, 

 becomes in 30 or 40 hours sulphuretted hydrogen, and hydrosul- 

 phuretted hydro-sidphocyanate of ammonia. 



Hydrosulphurettcd Hydrosulphocyanate of Ammonia. 



11. The proportions first stated are proper for the preparation 

 of this compound : the liquor is to be left on the first-formed 

 crystals until the second set begin to appear, generally about two 

 hours, at 60" Fahr. : it is then to be poured off, filtered rapidly 

 through paper moistened with alcohol, and left in a closed wide- 

 mowthed flask for ten hours, at about 50° Fahr. ; cooling the 

 liquor too suddenly sometimes causes the formation of a little of 

 the reddening salt; but towards the end of the crystallization it is 

 well to lower the temperature. After thirty hours, decant, wash 

 the broken crystals with small portions of alcohol, put the salt on 

 dry paper, and compress it powerfully. If the salt is to be pre- 

 served, finish the drying by an air-pump. 



