I 



1825.] Seleniurets of the Eastern Harz* 289 



Froportion to each other. But as the mineral is not crystallized, 

 cannot venture to pronounce decidedly on its composition.* 



I am convinced that a part, at least, of the copper in this 

 mineral may contain two atoms of selenium, although no sele- 

 nium sublimes, when an assay is heated in a small matrass, as 

 we might expect it to do. I fused seleniuret of lead with sele- 

 niuret of copper, prepared by heating copper filings with sele- 

 nium, and made the mass red-hot, so that it could not contain 

 any excess of selenium. The alloy of these seleniurets fused 

 rather more readily than seleniuret of copper alone. I found 

 that I could add a considerable quantity of pure selenium to this 

 alloy, without its being sublimed by heat. The alloy merely 

 became more fusible, and that in proportionto the quantity of 

 biseleniuret that it contained.^ 



4. Seleniuret of Lead with Seleniuret of Copper, in a differeno 

 Proportion. — The other more fusible specimen Hkewise gives no 

 sublimate when heated in a small matrass, provided it be pure. 

 A large quantity of the mineral, of a violet colour, gave, however, 

 a black sublimate by heat which had the appearance of selenium, 

 but afforded globules of mercury, when heated with soda in a 

 matrass, and proved to be a seleniuret of mercury. The deeper 

 the violet colour of these specimens, the larger is the quantity 

 of seleniuret of mercury that they contain, but I did not analyse 

 them, in consequence of the variable quantities of that seleniuret. 

 For the purpose of analysis, I selected portions that had not a 

 violet colour, which gave per cent. 



Selenium 34-26 



Copper. . 15 45 



Lead 47-43 



Silver 1-29 



Oxides of lead and iron 2*08 



100-51 1 



I have not deducted the oxygen of the 2-08, the weight of 

 the oxides of iron and lead, which is the cause of the shght 

 excess that I obtained. * 



47-43 of lead combine with 18*13 of selenium to form seleniu- 

 ret of lead, and 15*45 of copper with 9*69 of selenium to form 

 seleniuret of copper, and with 19*38 to form the biseleniuret. 

 What I have already said of the probable composition of the 



• A second analysis gave me 57*13 lead, and 9*56 copper; the latter, however, con- 

 tained some iron which was not separated from it. 



•f Some sulphurets exhibit similar phenomena. A compound of one atom of cobal 

 with four atoms of copper would lose sulphur by being heated in a matrass. It, how- 

 ever, loses nothing, if it contain arseniuret of cobalt, as in the grey cobalt. 



X On repeating the analysis I obtained 14-23 per cent, of copper, 50*27 lead, and 

 1 '09 silver. The difference between these two analyses is greater than should exist 

 between two analyses of a crystallized mineral. 



iVety Series, vol. x» u 



