There have also been introduced processes in which the chlorine is generated in the chloridizing vat, the reagents used being dilute solutions of bleaching powder and an acid.
The supernatant liquid is led into settling tanks, where a further amount of "gold is deposited, r and is then filtered through sawdust or sand, the sawdust being afterwards burnt and the gold separated from the ashes and the sand treated in the chloridizing vat.
According as a preliminary chloridizing roast has or has not been given, the process is classed as roast-amalgamation or raw-amalgamation.
In a chloridizing roast chlorine produces its effect as nascent chlorine or gaseous hydrochloric acid.
The ore is given only a partial chloridizing roast, on account of the great loss in silver that would be caused by the formation of zinc chloride.
Sodium chloride, characteristic of the Augustin process in which the ores, after a chloridizing roast, were extracted with brine, and the silver precipitated by copper, has almost wholly fallen into disuse; and potassium cyanide, which has become a very important solvent for finely divided gold, is rarely used in leaching silver ores.
As a rule the ore is subjected to a preliminary chloridizing roast, though occasionally it may be leached raw.