314 PROCEEDINGS OF SECTION B. 
some time on the cooling-floor. The percentage chloridised ranged 
from 71 per cent. to 86°36 per cent. (See Table I.) 
The loss in roasting amounted to 9:07 per cent., which represents 
the difference between the amount of silver in the ore mixture 
sent to the roaster, and that in the roasted ore and flue-dust sent 
to the vats ; the loss in dust is included in this amount. 
The leaching was carried on in the following way :— 
The ore was leached with cold water for five hours, the wash- 
water during that period being run into the wash-water precipitat- 
ing tanks. After five hours washing no silver was found in the 
wash-water which was then run to waste until the end of washing. 
The washed ore was then treated with eight charges of ordinary 
solution (hyposulphite of soda) of 1:5 per cent. strength, followed 
by a charge of standard extra, which stood in the charge, or was 
circulated for from four to six hours. This was followed by a 
charge of ordinary, and then by a second charge of extra of about 
one-half standard strength, then by two charges of ordinary solu- 
tion, and finally by wash-water. The solutions were used at a 
temperature of from 40 to 60 degrees centigrade. 
The above order of leaching was varied in one or two cases 
where delays occurred in the work, and more extra was used in 
an attempt to obtain a higher extraction. 
Circulation of the extra solution was found more efficacious than 
allowing it to stand in the ore. When the extra solution stands in 
the ore more than a few hours its effect is destroyed. 
The silver in the wash-water, which gave an acid reaction, was 
precipitated by sodium sulphide. The precipitation of the other 
metals in the wash-water was only partial. The wash-water pre- 
cipitate settled rapidly, and the liquid was run off immediately it 
cleared. The precipitation of the hypo. solution presented no 
peculiarities. The sodium sulphide was measured by a bucket, and 
the end of precipitation was found by filtration and testing in the 
usual way. The rate of filtration through the ore was rapid—about 
8 inches per hour. When the flue-dust was added daily to the 
roasted ore on the cooling-floor, in such a way as to become evenly 
distributed through it, no difference was found ; but on one occa- 
sion (H in the Table) the flue-dust was not properly mixed, and in 
filling formed a cone-shaped Jayer in the vat, which prevented 
completion of the leaching, and necessitated the retreating of the 
contents. On removing the ore from the vat, the portion above 
the flue-dust layer assayed only 15 oz., while the lower portion 
assayed over 30 oz. per ton; the whole, after reroasting, averaging 
35 Oz. 
It was generally found that the ore on top assayed much higher 
than the ore at the bottom of the vats. Vat F, for example, gave 
an average tailings sample assaying 3°9 oz. per ton, while ore 
taken from the upper portion assayed 3:1 oz.; from the middle, 
