106 Mr. D. Forbes on the Chemical Composition 



found in the analysis is precisely sufficient to combine with the 

 whole of the metals present and form sulphides with them, con- 

 sequently leaving no surplus whatever either of uncombined 

 metals or of sulphur. 



This will be evident from the following statement : — 



Sulphur . . 16-30 



Bismuth . . 27-00+ 6-11 Sulphur forms 33-11 Bi 2 S 3 



Lead . . . 33-00+ 507 „ 38-07 PbS 



Silver . . . 15-00+ 2-22 „ 17'22AgS 



Iron . . . 4-30+ 2'45 „ 6'75 FeS 



Copper. . . 0-90 + Q-45 „ 1-35 CuS 



96-50 16-30 Sulphur. 96-50 



Antimonial Silver. — Discrasite. 



Amongst the argentiferous minerals found in Chanorcillo, 

 Domeyko* enumerates, without further description, a combina- 

 tion of antimony and silver, which yielded to his analysis 



Silver 064 



Antimony .... 0*36 



roo 



From these results, it will at once be seen that this mineral 

 must be totally different in composition from either of the varie- 

 ties of discrasite hitherto described, and which have respectively 

 the following formulae and percentage composition : — 



A§6Sb \ Antimony '. 166 Ag4Sb \ Antimony I 230 



1000 100-0 



So that this new compound is probably represented by the for- 

 mula Ag 2 Sb, which would require 



Silver 62-61 



Antimony. . . . 37'39 



Toaoo 



Besides this mineral, another compound of antimony with 

 silver is also found, and much resembles in appearance native 

 silver, especially when burnished, but can easily be rubbed to 

 powder in a mortar, which at once distinguishes it. A specimen 

 of this mineral obtained from the mine Bosario contained, accord- 

 ing to Domeyko, 



Silver 94-2 



Antimony . . . . 5*8 



100-0 

 * Tratado de Ensayes, 2nd edit. p. 238. 



