Chemical Hintory of Mercury. 293 



consistent with one proportional of mercury and one of sulphur. 

 Like the protoxide, however, it is singularly easy of decomposition. 

 Trituration effects tliis, so does exposure to the sun's rays, so does a 

 heat of 300° ; and when heated in a glass tube in the flame of aspirit 

 lamp, mercury distils over, and bisulphuret is sublimed. 



The pharmaceutical preparation, called Ethiops-mineral, is gene- 

 rally stated to be a mixture of sulphur and black sulphuret of mer- 

 cury ; indeed it is called, in the latest edition of the London Phar- 

 raacopceia " Hydrargyri Sulphuretum Nigrum." It has long had 

 a place in the materia medica, though a very useless and inert 

 compound. It is a black powder, prepared by triturating to- 

 gether equal weights of mercury and sulphur, until globules are no 

 longer visible. When properly made it may be rubbed upon gold, 

 without leaving any mercurial stain upon that metal; hence it ap- 

 pears that the mercury is in chemical combination with the sulphur, 

 a circumstance indeed sufficiently evident from the great rise of 

 temperature that ensues when the materials are subjected in large 

 quantities to powerful trituration ; they then smoke and agglutinate. 

 Fourcroy and several other chemists have regarded this compound 

 as consisting of sulphur and black oxide of mercury; but Prout 

 and others have amply demonstrated the fallacy of such an opinion, 

 without however showing the real nature of the substance. It has 

 lately been usual to describe it as a mixture of sulphur and black, 

 or protosulphuret of mercury; and it is stated in several pharma- 

 ceutical works of authority* to be " insoluble in nitric acid, but to- 

 tally dissolved by a solution of pure potassa." An inquiry into the 

 truth of this assertion, so contrary to what one would expect d 

 priori, has, I think led to a satisfactory explanation of the nature of 

 Ethiops-mineral. 



A portion of well-prepared Ethiops-mineral was boiled in solu- 

 tion of potassa until no further action took place ; the liquor was 

 then decanted off, and fresh portions of the alcaline solution added, 

 the boiling being repeated as before, until no further action ensued. 



* Duncan's Edinbuigli New Dispensatory. Thomson's London Dispensa- 

 tory. Paris, Pharmacologia. 



