1 and 2.
Directly above this last vat there is a water hose, supplied with a
flexible spout, through which a strong stream of water is directed upon
the amalgam as it issues from the grinding vat, in order to wash off all
impurities.
The following is the mode of working usually employed. The grinding vat or
tina is first charged to about one-fifth of its depth with water and from
6 cwt. to 7 cwt. of common salt. The amount of salt required in the
process depends naturally on the character of the ore to be treated, as
ascertained by actual experiment, and averages from 150 lb. to 300 lb. per
ton of ore. Into this brine a jet of steam is then directed, and the
stirrer is set to work for about half an hour, until the liquid is in a
thoroughly boiling condition, in which state it must be kept until the end
of the process.
As soon as the liquid reaches boiling point, the stamped and roasted ore
is run into the vat, and at the end of another half-hour about 1 cwt. of
mercury is added, further quantities being added as required at different
stages of the process. The stirring is kept up continuously for eight to
twelve hours, according to the character and richness of the ores.
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