472 



weights of the substances they represent. The numbers in 

 column (3) are the same as those in (2), with the exception 

 that the quotients for the lead and iron are added together. 

 In (4) we have other numbers in the same ratio as the 

 preceding. A mere inspection of the latter is sufficient 

 to show that the empirical formula of the mineral is 

 S 9 Pb 6 Sb! ; and such being the case, there can be no doubt 

 that the rational formula is 



6 (S, Pb) + S 3 , Sb, 

 or that it consists of six atoms of sulphuret of lead associated 

 with one atom of tersulphuret of antimony, a little of the 

 former metal being replaced by an equivalent quantity of 

 iron. 



The above are the particulars of the analysis which ap- 

 peared on the whole to have been most successfully per- 

 formed ; the analysis, however, was repeated three times, 

 and the results in each instance conducted to the formula 

 just given. In the first trials, in consequence of strongly 

 heating the ball traversed by the chlorine from the very 

 commencement of the experiment, some of the chloride of lead 

 was volatilized, and Dr. Apjohnwas led to conclude the con- 

 stitution of the mineral to be materially different from what it 

 afterwards proved to be. The ball should not be heated 

 until the spontaneous action of the chlorine on the ore has 

 ceased. 



Kilbrickenite, as Dr. Apjohn proposed to call this mineral, 

 is obviously what Berzelius denominates a sulphur salt, i. e., 

 a combination of an electro-negative with an electro-positive 

 sulphuret. But there are several other ores known to mine- 

 ralogists composed of the same proximate constituents, or 

 including sulphuret of lead in association with the sulphuret 

 of antimony. The subjoined list comprehends those which 

 have been analysed and described. 



