On the Combinations tf the Metats toith Sulphur, 309 



t?ie oxigeh of the water, that of the fulphur on the hidrogen of the fame fubftance, and 

 bftly, that of the metallic oxide formed, for the muriatic acid. In this circumftance ful- 

 phurated hidrogen gas isconftantly difengaged. 



The fulphuric acid which does not decompofe the fulphurated oxide of iron, unlefs it be 

 concentrated and boiling, decompofes the fulphuret of iron without heat, and the more 

 readily when it is diluted with a certain quantity of water. The reafon of this evidently 

 tequires no explanation. 



Though a great quantity of water oppofes the aflion of the acids on the metallic ful- 

 phurets in general, nevcrthelefs it is lefs noxious with refpeft to that of iron than with 

 legard to the others, becaufe the fulphurated hidrogen does not decompofe the folutions o£ 

 iron in the acids. 



Concerning the Sulphuret of Lead. 



In the natural fulphuret of lead or galena, lead exifts in the metallic ftate;. for which reafon^ 

 when this mineral fubftance is brought into conta£t with the muriatic acid, fulphurated 

 hidrogen is formed even in the cold. It appears even when the fulphur is united to the 

 oxide of lead j this metal lofes its oxigen in order to unite with the fulphur, for we obtaia 

 a matter perfeftly fimilar to natural galena. The manner in which the redu£lion of lead. 

 is here efFefted may be eafily underftood. A portion of fulphur combines with the oxigen 

 and forms fulphuric acid^ which the heat volatilizes, and another portion unites with the 

 metallic lead» The reduiSlion of lead and the formation of galena take place nearly in 

 the fame manner, when a folution of this metal in an acid is mixed with a folution of 

 fulphurated hidrogen, or of any hidro-fulphuret whatever. There is neverthelefs this 

 difference, namely, that in this cafe the hidrogen takes the oxigen from the lead, and 

 forms water at the fame time that the fulphur and the metal, which meet in a ftate of ex- 

 treme divifion, combine without heat in the midft of the fluid. There is alfo another dif- 

 ference, that the galena formed by this procefs contains rather more fulphur than the na- 

 tural compound, as is proved by the fmall quantity of fulphur which feparates from thi^- 

 fubftance at a very gentle heat, and then leaves it abfolutely in the fame ftate as common 

 galena. 



From thefe fa£\:s it follows that the muriatic acid, and probably all other acids aft oft- 

 the oxide of lead by their mafs and their concentration^ that when thefe two forces, c* 

 even one of them is deftroyed, or fimply weakened, the fulphurated hidrogen deprives 

 them of the lead ; but whatever may be the quantity and concentration of the acid united* 

 5vith the lead or other metals, the decompofition of the fait will take place if an hidro- 

 fulphuret be employed in fufficient quantity. 



It is not Angular that the affinities of the acids fbrthe metallic oxides fhould be Weak- 

 tned by water, nor that their adion on thefe fubftances ftiould be more energetic by virtue 

 of their maffea. Antimony, mercury, bifmuth, and lerid itfelf, afford ftrikifig examples 

 of thiSf 



It 



