1S26.] Seleniurets of the Eastern Harz, 28? 



residuum of chloride of silver, or any portion of the mineral 

 undecomposed. Another portion of the mineral weighing 3*327 

 grammes gave 0*918 gr. of selenium, or 27*59 per cent. These 

 results agree pretty well with the calculated composition of the 

 mineral, according to which seleniuret of lead is composed of 

 72-3 lead and 27*7 selenium. 



To ascertain whether this mineral contain any trace of sulphur 

 not discoverable by the blowpipe, a portion was treated with 

 chlorine, and the sublimate made to pass into water. The 

 liquid was rendered very acid with muriatic acid, and muriate of 

 barytes dropped into it; but not the shghtest precipitate of 

 sulphate of barytes could be perceived. The same experiment 

 was repeated with several other specimens of seleniuret of lead, 

 and always with the same result. 



2. Seleniuret of Lead, with Seleniuret of Cobalt. — M. Zinken 

 sent me only one specimen of this mineral, adding that it has 

 great resemblance as to its elements to a mineral found at 

 Clausthal, which Mr. Hausmann named Kobaltbleierz, Exter- 

 nally it resembles seleniuret of lead, and like it is disseminated 

 in magnesian carbonate of lime, from which it may be freed by 

 diluted muriatic acid. Its nature is easily detected by the blow- 

 pipe. It gives a sublimate of selenium when heated in a small 

 tube closed at one end, and evinces the presence of cobalt by 

 fusion with the fluxes on charcoal. In other respects it behaves 

 before the blowpipe like seleniuret of lead. By treating 1*782 

 grammes (28 grains) with chlorine, I obtained 0*56 grammes (8*65 

 grains) of selenium, and a little iron. The fixed chlorides 

 dissolved entirely in water without leaving any residuum. The 

 lic]^uid was evaporated to dryness after the addition of sulphuric 

 acid ; the dry mass heated to expel the excess of acid, and 

 mixed with water. It left 1*668 gramme (25*8 grains) of sul- 

 phate of lead, equivalent to 1'139 gramme (17*6 grains) of lead. 

 I then threw down the oxide of cobalt by caustic potash, but 

 the filtered liquid still contained a little cobalt, which was pre- 

 cipitated by hydrosulphuret of ammonia. The whole quantity 

 of cobalt obtamed was 0*056 gramme (0*87 grain), and it still 

 contained traces of lead and iron, which were not separated 

 from it. The result of the analysis per cent, is. 



Lead 63*92 



Cobalt 3*14 



Selenium 31*42 



Iron ..f,^.... 0*45 



Loss ..,..;;. 1-07 



100-00 

 The composition of this mineral appear^ to be analogous ta 



