Silver. 249 



22. The white refiduum, containing the 

 fulphur, arfenic and iron, is next to be ex- 

 amined : by boiling it in fpirit of fait, the 

 arfenic and iron are taken up; the arfenic is 

 to be precipitated by the addition of water, 

 and then the iron by the Prujfian alkali ; the 

 fulphur remains undiflblved, and may be 

 treated with volatil alkali to try whether it 

 retains any copper or horn filver. 2 Bergm. 

 418. 



SPECIES IX. 



Mineralized by Arfenic and Sulphur^ with a 

 large Proportion of Copper andfome Iron. 



Grey Silver Ore, Fahl erz, 



23. This is a hard, grey, or dark grey fub 

 ftance, more or lefs brilliant, fometimes cryf- 

 talized, but moftly amorphous, and is, irj 

 fal, the grey copper ore hereafter to be 

 mentioned, Chap. 4. N* 26, impregnated 

 with filver, and varies much in its contents 

 from about i to 12 per cent, of filver, and 

 from 12 to 24 of copper, the remainder be- 

 ing fulphur and arfenic, with a little iron : 

 the richer it is in copper, the poorer in filver, 

 and reciprocally. Mr. Monnet remarks, that 

 wherever copper is united to arfenic, filver is 

 alfo found ; it is the comm:>neft of all the 

 filver ores : the grey filver ore of Dal \i\ 



