Details of the Amalgamation Process, as practised at Halsbrücke

—All ores which contain more than 7 lbs. of lead, or 1 lb. of copper, per cent., are excluded from this reviving operation ( an quick ver fah ren ); because the lead would render the amalgam very impure, and the copper would be wasted. They are sorted for the amalgamation, in such a way that the mixture of the poorer and richer ores may contain 7 1 ⁄ 2 , or, at most, 8 loths (of 1 ⁄ 2 oz. each) of silver per 100 lbs. The most usual constituents of the ores are, sulphur, silver, antimonial silver (spei glanzsilber), bismuth, sulphurets of arsenic, of copper, iron, lead (nickel, cobalt), zinc, with several earthy minerals. It is e ential that the ores to be amalgamated shall contain a certain proportion of sulphur, in order that they may decompose enough of sea salt in the roasting to disengage as much chlorine as to convert all the silver present into a chloride. With this view, ores poor in sulphur are mixed with those that are richer, to make up a determinate average. The ore-post is laid upon the bed-floor , in a rectangular heap, about 17 ells long, and 4 1 ⁄ 2 ells broad (13 yards and 3 1 ⁄ 2 ); and upon that layer the requisite quantity of salt is let down from the floor above, through a wooden tunnel; 40 cwts. of salt being allotted to 400 cwts. of ore. The heap being made up with alternate strata to the desired magnitude, must be then well mixed, and formed into small bings, called roast-posts , weighing each from 3 1 ⁄ 2 to 4 1 ⁄ 2 cwts. The annual consumption of salt at Halsbrücke is 6000 cwts.; it is supplied by the Pru ian salt-works.