30 Examination of a Native Sulphur et of Bismuth. 



It lias exteriorly an iron-gray colour, sometimes with a bis- 

 muthic tinge, and in its cleavage surface possesses a lustre ap- 

 proaching that of polished steel. Its specific gravity is 5'85, 

 and its hardness = 2'7. When heated before the blowpipe 

 on charcoal it inflames, and by increasing the heat for some 

 time, appears to be entirely volatilized, with the exception of 

 a minute globule of brown scoriaceous matter. 



On examination it was found to contain bismuth, sulphur, 

 copper, iron, and siliceous matter. The first analysis was per- 

 formed by acting upon the mineral, reduced to a very fine 

 powder, with nitre-muriatic acid, until the whole of the sulphur 

 was acidified ; this was conducted in a small stoppered retort, 

 to which a receiver was attached, in order to collect any small 

 quantity of sulphur that might be carried over mechanically 

 during the digestion. The solution thus obtained was diluted 

 with water, and filtered to separate the silica ; a solution of 

 nitrate of baryta was employed for the precipitation of the sul- 

 phuric acid, and the sulphate of baryta (and also the silica) 

 washed at intervals with warm dilute nitric acid, to remove any 

 small quantity of bismuth which might fall by the gradual 

 dilutions. After the separation of the excess of baryta, am- 

 monia was added in slight excess, which threw down the oxides 

 of bismuth and iron, and held the oxide of copper in solution ; 

 by evaporation to dryness and the addition of potassa tfiis 

 oxide was obtained. 



The mixed oxides were then acted upon by dilute muri- 

 atic acid, added in small quantity; the oxide of iron was thus 

 completely removed, and the dichloride of bismuth which 

 remained, after being digested in a weak solution of potassa, 

 was collected as an oxide : the iron was again precipitated 

 from its muriatic solution by ammonia. 



Although this analysis was conducted with the greatest 

 care, and repeated in order to avoid ambiguity, yet the results 

 in both cases exceeded the weight of the mineral employed. 

 Upon heating the oxide of bismuth obtained in the second 

 analysis, before weighing (and which was performed in a 

 small tube of green glass sealed at one of its extremities), it 

 was observed that a small quantity of white opaque vapour 

 arose and appeared to be condensed upon the upper part of the 

 tube, and on adding distilled water to it, a precipitate of di- 

 chloride of bismuth was instantly formed, proving it to have 

 been sublimed chloride of that metal. The oxide itself was next 

 examined; by dissolving it in pure nitric acid, and testing the 

 solution with nitrate of silver, a small quantity of chloride of 

 silver was thrown down. 



Having ascertained these facts, a solution of muriate of 



bismuth 



