_--The mother acid is
pumped from C to the reservoir, B, for this purpose an iron pipe
connecting the top of B with a recess in the bottom of C. The tank, B,
is cast as a closed vessel, with a manhole in the top, which is
ordinarily kept closed by an iron plate resting on a rubber packing.
The air is exhausted from B by a steam injector, and the acid rises
from C and enters B without coming in contact with any valves. The
volume of fresh commercial acid necessary for another dissolving
operation, say 800 pounds, more or less, for refining 800 pounds of
bullion in A A, is lifted from some other receptacle into B in the
same manner. The mixture of the two acids in B now represents the
volume of acid to be employed for dissolving and settling the next
charge of 800 pounds of bullion in A A. In this reservoir, B, the
cloud of lead sulphate mentioned above finds an opportunity for
settling.
The crystals of silver sulphate are detached from C by an iron shovel
and thrown into D. D is a lead lined tank about 4 ft. by 4 ft. and 3
ft. deep. It is divided into two compartments by means of a
horizontal, perforated false bottom made of wood. From the lower
compartment a lead pipe discharges into the lead lined reservoir, E.
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