188 On Stilphiret of Carltm. [Marc^, 



the carl>o-sulphuret of lead be allowed to stand, it decomposes 

 itseU, and after L'4 liours it forms a black mass, consisting of car- 

 bonate of lead, which is soluble with effervescence in muriatic acid, 

 end of sulphuret of lead which is not soluble. It appears that the 

 carbon oxidates itself at the expense of the oxide of lead, and that 

 the reduced portion of metal combines with the sulphur. The 

 carbo-sulphuret of lead is equally ])roduced when pulverized oxide 

 of lead is mixed with carbo-sulphuret of potash. If the oxide be 

 quite pure, it assumes a fine blood-red colour. The carbo-sulphuret 

 of lead is also formed by digesting oxide of lead with sulphuret of 

 carbon, mixed with a few droj« of water; but it decomposes itself 

 immediately after being formed. Without the intervention of water, 

 tlie oxide of lead does not appear to exert any action on the sul- 

 phuret of carbon. 



Nitrate of Copper. — A dark brown precipitate, almost black ; 

 after a few hours it becomes perfectly black, and then consists of 

 carlxmate and sulphuret of copper. 



Muriate of Oxydnle of Mr.rcuri/. — A black precipitate. 



Muriate o/' Oxide of Mercury. — An orange coloured precipitate, 

 which was neither altered nor dissolved by muriatic acid. 



Muriate of Silver. — A red-brown precipitate, which is decora- 

 posed and turns black in less than half an hour. 



There remained to be ascertained whether the sulphuret of carbon 

 eombine vvitli the metals in tlieir reguline state, or whether the 

 metals, in combining with the sulphur, separate the carbon from it. 

 Potassium was selected for this inquiry. A small glass ball, filled 

 with sulphuret of carbon, was introduced into a retort. The rapil- 

 Jary orifice of the ball, by which it had been filled, was hermetically, 

 closed. A small platina tray, containing some melted potassium, 

 was also introduced into tlie retort, which was afterwards quickly 

 exhausted. The ball was then broken by giving a ierk to the 

 retort, and the sulphuret was instantly volatilized in the vacuum. 

 Heat being now applied, the potassium inflamed, and burned with 

 a red flame. The product was black, and not easily soluble in 

 water. The solution was black and opaque, and deposited some 

 very pure charcoal. This proves that the sulphuret of carbon had 

 been decomposed by the potassium. The l)lack solution did not 

 contain any sulphuret of carbon, but it contained a little carbon in 

 fiU unknown stale of combination. The solution, in decomposing 

 itself by exposure to the air, deposited some sulphur, which had a 

 greyish tinge, in consequence of a little carbon being mixed with it. 



2. On the Oxidulated Sulphuret of Iron. — This substance (which 

 is alluded to in the paper on the sulphuret of carbon, p. 1^7) being 

 not generally known, it may be proper to give a short account of it. 

 It is ol)tair.ed by mixing together in a retort some pulverized red 

 oxide of iron and sulphur, and heating the mixture at a moderate 

 heat, until no more sulphurous acid comes over. It is necessary to 

 apply the heat gently, in order to prevent the formation of a metallic 

 sulplmret. The oxidulated sulphuret oi' iron is pulverulent, has » 



