If the lead is to be liquated and then brought to a bright-red heat, both operations are carried on in the same reverberatory furnace.
The liquated zinc-silver-lead crust contains 5-10% silver, 30-40% zinc and 65-50% lead.
The retort is pear-shaped, and holds1000-1500lb of charge, consisting of liquated crust mixed with 1-3% of charcoal.
This method is rarely practised except by the rollers of zinc. A certain amount of refined zinc can be dipped from the furnace; a further amount, nearly free from iron, can be liquated out of the ingots cast from the bottom of the bath in a subsequent slow remelting, and it is sometimes possible to eliminate a zinciferous lead which collects in the sump of the furnace.
It is also manufactured by the latter process from the metallic zinc liquated out of galvanizer's dross.
Antimony, however, occurs chiefly as the sulphide, stibnite; to a much smaller extent it occurs in combination with other metallic sulphides in the minerals wolfsbergite, boulangerite, bournonite, pyrargyrite, &c. For the preparation of metallic antimony the crude stibnite is first liquated, to free it from earthy and siliceous matter, and is then roasted in order to convert it into oxide.