Its more general application has been hampered,
however, by the circumstance that the patent had been secured by one
firm which limited itself to its utilization in its California works.
The patent having expired, the author lately introduced a modification
of the process by which the apparatus and manipulations are greatly
cheapened and simplified. In the following account is given a short
description of the process in its present shape.
_Preparing the Silver Sulphate._--The bullion, containing,
essentially, silver, copper and gold, is dissolved by boiling with
sulphuric acid in cast iron pots. The difference between the new
process and the usual practice consists in the use of a much larger
quantity of acid. Thus, in refining ordinary silver "dore," four parts
of acid are used to one part of bullion. Of this acid one part is
chemically and mechanically consumed in the dissolving process, and
the remaining three parts are fully recovered and at once ready for
reutilization, as will be described hereafter. In the usual
process--understanding thereby, here and in the following, the process
practiced at the United States mints, for instance--two parts of acid
are employed for one of bullion; all of this is lost, partly through
the dissolving and partly in being afterward mixed with water,
previous to the precipitation of the silver by copper.
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