of some Chilian Minerals. 107 



• 



with traces of arsenic ; other specimens are stated to have yielded 

 from 4 to 6 per cent, of antimony along with some arsenic. It 

 would therefore appear probable that this mineral is represented 

 bv the formula Ag 18 Sb, which requires 



Silver 9378 



Antimony . . . . 6*22 



100-00 

 We consequently now have no less than four distinct compounds 

 of silver with antimony, represented respectively by the formulse 



Ag 2 Sb, Ag 4 Sb, Ag 6 Sb, and Ag 18 Sb. 



Arsenio-antimonide of Silver. 

 This mineral occurs in the form of grains disseminated through- 

 out carbonate of lime, and is very similar in appearance to native 

 silver. On treating the mass with acetic acid, the carbonate of 

 lime dissolves and the mineral remains behind in the form of 

 brilliant metallic grains, which, when submitted to the action of 

 the blowpipe, emit abundant fumes of arsenic and antimony. 

 The analysis by Domeyko afforded respectively, 



Silver .... 53-6 533 



Iron .... 3-0 3-0 



Arsenic . . . 23-8 22'3 



Antimony. . . 19*6 21'4 



1000 1000 



Upon calculation, it will be found that the equivalents most 

 approximating to these results are 10 Ag, 2Fe, 6 As, and 3Sb, 

 which will give the following percentage composition : — 



10 /lOAg = 54-73 Silver. 

 l '\ 2Fe = 2-84 Iron. 



6As = 22-81 Arsenic. 



3Sb = 19-62 Antimony. 



100-00 

 Considering the iron to replace a part of the silver, we have 

 the formula (AgFe) 4 (As Sb) 3 . Domeyko looks upon the iron 

 as being in the state of biarsenide*, and considers that the rest 

 of the arsenic, along with the antimony and silver, are combined 

 to form Ag 2 (As Sb) 3 , which he considers is equivalent to a com- 

 bination of one atom sesquiarsenide of silver with one atom se3- 

 quiantimonide of silver. 



Arsenide of Silver. 

 Whilst in Copiapo several specimens were given me under 

 this name, but, upon submitting these to chemical examination, 



* Elementos de Mineralogia, 2nd edit. p. 190. 



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