British Mineralogy, 353 



subsequently dissolved out by water allowed the sulphate of lead 

 to be determined. 



The filtrate, which now contained the iron and zinc, was added 

 to that previously obtained from solution B, and the whole pre- 

 cipitated by hydrosulphate of ammonia, after previous neutraliza- 

 tion of ammonia. The sulphides thus obtained were oxidized 

 by nitric acid and separated by ammonia, when both these metals 

 were determined as usual. 



To determine the sulphur, a separate portion of the mineral 

 was acted upon by nitrohydrochloric acid, evaporated nearly to 

 dryness, a small amount of free sulphur removed and estimated 

 separately after deduction of a minute quantity of residue left 

 upon ignition, and the solution, after filtration from insoluble 

 matter, was precipitated by chloride of barium, and the amount 

 of sulphate of barytes determined as usual. 20*01 grs. of mineral 

 afforded 0*50 free sulphur, along* with 36*41 grs. of sulphate of 

 barytes ; it consequently contained 27*4.1 per cent, of sulphur. 



The other results obtained were as follows : — Mineral employed 

 and treated by chlorine, 20*02 grs. ; sulphate of lead obtained, 

 0*39 gr. ; insoluble quartz, 0*07 gr. ; chloride of silver, 3*61 grs. ; 

 sulphide of antimony with free sulphur, 13'22 grs.; antimo- 

 niate of soda from 4*04 grs. ditto, 2*88 grs. ; oxide of zinc, 1*16 

 gr.; sesquioxide of iron, 1*38 gr.; sulphate of copper, 12*53 grs. 



The above data will upon calculation show the percentage 

 composition of the mineral to be as follows : — 



Sulphur .... 27'48 



Antimony . . . 24*85 



Silver 13*57 



Copper .... 22*62 



Iron 4*80 



Zinc 4*65 



Lead 1*43 



Quartz _0*34 



99*~74 

 Arsenic and mercury were carefully sought for, but not found 

 to be present in the mineral. Subtracting the amount of quartz 

 and dividing the loss on analysis equally amongst the consti- 

 tuents, we have — 



Sulphur .... 27*48 27*64 



Antimony . . . 24*85 25*00 



Silver 13*57 13*65 



Copper .... 2262 22-76 



Iron 4-80 4-82 



Zinc 4-65 4*69 



Lead 1'43 1-44 



99-40 100*00 



