102 ON A METHOD OF EXTRACTING GOLD, SILVER, 
I then calcined 400 grs. of pyrites, mixed the residue with 
200 grs..of raw ore and again calcined, then added 100 grs. of 
raw ore, and continued the operation until fumes were no longer 
evolved, when the residue was found to contain 6°46 per cent. of 
ras oxide. This process was therefore of no value; but I 
noticed that after each addition of pyrites considerable e quantities 
of white vapours were evolved, and as the ore contained but little 
arsenic this could only arise from ‘te formation of sulphuric 
. anhydride. I therefore proceeded to determine how much sul- 
phuric acid could be obtained by calcining a mixture of raw 
pyrites and roasted residue 
A combustion tube was fitted with a 5 smaller tube lea ding 
through water in a Woolfe’s bottle, the second neck of which 
was connected with an aspirator, and mixtures of raw and roaste 
pyrites were heated to a dull-red in the combustion tube, a 
current of air being maintained through the whole apparatus, 
this 
the ore “occasionally oo with a be 7a wire. In 
n 
me a acid was determined in pales — 
pe a ue pare. bs ium sulphate... 365 grs. 
er gave barium sulphate 35° BB. 55 
cael on the 100 grs. used, this gave— 
Sulphuric acid in residue = 8°68 sulphur. 
vi an water — =19'86 “eo 
Total... 98°5: 54 sulphur. 
Similarly, — grs., with 20 om residue oul 
piers poe, barium sulphate - ... 31°69 grs. 
2s, ON OD » 
which eis on 100; grs, u used wan ve— 
Sulphuric acid in eee = — 70 lee 
9-00 
” ” 
Total... 27°70 70 sulphur. 
ucing the roasted ore to 15 grs., a smaller return was 
On red 
obtained ; but these results anak that by. proper management © 
nearly three-fourths of the saber pr resent in the ore could be 
‘ 
Be 
sy 
Sede ae ee A LS Ce Te cee ae oe ne 
