According to the foregoing reactions, Workable Lead consists of, Lead, Copper-traces, Arsenic, Antimony, and sometimes traces of 3. Impure Tin. On charcoal in the oxidating flame it behaves, as regards its easy oxidation, like pure tin. In the reducing flame, it gives a coating of oxide of tin, mixed with a dark yellow powder, which exhibits a lemon-yellow color on cooling, and appears therefore to be oxide of bismuth. As a confirmation, another part of this tin was melted with microcosmic salt on charcoal, first in the oxidat-ing flame, and then in the reducing flame. The glass bead was, while hot transparent, but on cooling, became black and opaque, which indicated the presence of bismuth. Melted with borax, on charcoal in the reducing flame, a glass was produced, which was colored pure vitriol-green, by protoxide of iron. The tin was contaminated with bismuth and iron. 4. Black Copper, very Impure. Heated strongly in the open glass tube, it eliminates a little sulphurous acid, recognized by the introduction of moistened litmus paper. At some distance from the assay, a very slight white deposit is formed, having the appearance of oxide of antimony. On charcoal, per se, it melts with difficulty, yielding a sublimate of oxide of lead only. Melted together with proof lead and boracic acid, in such a manner that one side remains free, while the lead dissolves, a distinct sublimate of oxide of antimony is produced. The remaining part of the metallic globule, which is free from lead, has a greyish-white color, and is scopiform. The black copper, melted with borax on charcoal, in the reducing flame, produces a glass colored blue by cobalt, which melts on a platinum wire in the oxidating flame, appearing, while hot, green, and on cooling, blue-cobalt and oxide of iron. The metallic globule remaining, after treatment with boracic acid, produces, with microcosmic salt, on charcoal in the oxidating flame, a glass, which appears of a beautiful green, both when hot and cold, and becomes opaquish-red with tin-nickel and copper. The remaining undissolved metallic globule still appears greyishwhite, and is extremely dentritic. This appearance indicates the presence of arsenic, which is combined with nickel, and cannot be separated from this metal, either by boracic acid or microcosmic salt. A separate examination for arsenic, according to page 235, indicates the presence of this metal. This Black Copper consists of— Lead, Copper, Nickel, Cobalt, Iron, Antimony, Arsenic, Sulphur; and, according to a separate examination, a little Silver. 5. German Silver, or White Copper—Argentan. No change ensues, when it is heated in a glass tube. Melted on charcoal, in the reducing flame, it affords a sublimate, which is yellow while hot, and white when cold; with solution of cobalt, it assumes a beautiful green color, and therefore may be regarded as oxide of zinc. The globule, melted per se, on charcoal, and treated with borax in the outer flame, till those metallic oxides, irreducible in the inner flame, are dissolved, should be remelted in the reducing flame to separate the metals. The glass thus obtained is blue, and does not change its color when fused on a platinum wire in the oxidating flame. Cobalt only is therefore dissolved. U The metallic globule, freed from cobalt and melted with microcosmic salt, on charcoal, in the oxidating flame, gives a glass colored dark green. A portion of this vitreous mass, treated with more microcosmic salt, on platinum wire, in the oxidating flame, affords a bead which, on cooling, remains of a beautiful green-copper and nickel. This bead, on being removed, and treated on charcoal with tin, becomes opaque-red on cooling, owing to the presence of copper. The globule remaining undissolved, after treatment with microcosmic salt, is perfectly malleable, appears reddish-white, and consists, as it indicates a trace of silver only on cupellation, of copper and nickel. The composition of this alloy, is, therefore Copper, with a trace of Silver, Nickel, with some Cobalt, and Zinc. |