Important: Safety Warning
This page describes trade processes that use dangerously toxic materials such as cyanide solutions, mercury amalgams, or strong acids. These processes require training, equipment, and precautions far beyond what the text describes.
This information has been left in for historical purposes but should not be acted upon.
Semi-steel
See PUDDLED STEEL.
Separating-machine (Woodruff's) is an ingenious combination of vibrating screen and fan for extracting shot and other small iron from foundry refuse. it occupies ground space about four by eight feet; requires about one and a half to two horse-power to drive it; can be set up anywhere, in doors or out, under shed, where power can be had.
A barrowful of refuse will pass through the separator in three or four minutes, all the iron being deposited in box provided for it, and all other materials thrown to rear of machine.
Separating Metals from their Alloys.--Tin may be separated from copper by digesting in nitric acid, which dissolves the copper--the tin remaining in an insoluble peroxide.
Copper is separated from lead by adding sulphuric acid to the nitric solution and evaporating to dryness, when water digested on the residuum will dissolve out the sulphate of copper, leaving the sulphate of lead behind. From this solution the oxide of copper may be precipitated by pure potassa. The precipitation of copper in the metallic state is obtained by immersing polished steel into the solution.
Copper is separated from zinc by sulpuretted hydrogen, which will throw down a sulphuret of copper, which may be dissolved in nitric acid and precipitated as before.
Silver is separated from copper by first reducing the alloy to powder, and then digesting in a solution of chloride of zinc, which dissolves the copper, leaving the silver unchanged. Or, mix sulphuric acid 1 part, nitric acid 1 part, water 1 part; boil the metal in the mixture till it is dissolved, and add a little salt, which will cause the silver to subside. Copper is separated from its numerous alloys--as lead, tin, antimony, iron, bismuth, etc.--by melting the alloy, and fusing for about an hour with one part each of black oxide (copper scales) and bottle-glass to every ten parts of the alloy. The copper will fall to the bottom of the crucible; the other metals and impurities either volatilize or dissolve in the flux. If lead and tin are in solution, the lead may be precipitated by sulphuric acid, and the tin with sulphuretted hydrogen gas. In an alloy the lead will dissolve in nitric acid, leaving the tin as an oxide. Zinc and iron may be removed from plumber's solder by digesting the grain metal in diluted sulphuric acid. The acid first dissolves the zinc, then the iron, and all traces of these metals are removed by subsequent washing. Tin may be separated from Britannia and similar alloys by melting the metal and sprinkling sulphur over it; after which stir the metal in the crucible for a while, and the other metals will burn out, leaving the tin pure. Gold is separated from silver by melting the alloy and pouring from a height into a rotating vessel containing cold water. This granulates the alloy, which is then treated with nitric acid and heated. The product is nitrate of silver, which is reduced in the ordinary manner, and metallic gold as a black mud, which is washed and remelted.