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.
Arsenic
Arsenic is sometimes found pure, but more generally combined with nickel, cobalt, sulphur, and iron. To separate arsenic from the ores, they are first crushed and the arsenic dissipated in a reverberatory furnace by roasting, when the arsenious acid is condensed into white arsenic. The metal is obtained from white arsenic by incorporating it with carbonaceous matter and heating in a closed crucible provided with a receiver, in which the arsenic is condensed as a brittle white metal with a slight degree of lustre; the specific gravity of which is 5.7, its melting-point being 400 deg. At 500 deg. it volatilizes without fusing, the vapor having a strong tincture of garlic. The metal may be powdered in a mortar.
The chief property of arsenic is to promote the union of metals that would be otherwise difficult to mix--aluminum with iron; lead with zinc; lead with iron, etc. It promotes the fusion of many metals, and occasions some refractory ones to melt at a low temperature. Being a union rather than a true alloy, it is customary to call all alloys of arsenic by the name of arsenides. While arsenic, like antimony, tends to crystallize other metals, they are not rendered as brittle as the latter metal makes them. Nearly all metals combine with arsenic; but, except in the case of silver and gold, such alloys may be decomposed by lengthened fusion. White tombac is copper alloyed with arsenic. The metal for lead-shot is rendered more fusible and solid by a slight proportion of this metal, and gold may be permanently alloyed to form a brittle arseniuret of gold by exposing the heated metal to its vapors. From 1/4 to 3/4 of an ounce to the pound of any alloy will materially assist in preventing a tendency to porosity, but will result in a harder casting, somewhat lighter in color. Speculums and all similar objects are, by means of this metal, made hard, white, and lustrous.
For the manner of fluxing alloys of arsenic, also the methods employed for introducing this metal into the crucible, and alloys containing arsenic, see SPECULUMS; TOMBAC; LEAD-SHOT; COBALT.