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GOLD. 2 I 5

of one or two persons. For the purpose of the dentist, how-
ever, it will be sufficient to fix the draw-plate securely be-
tween the jaws of a bench-vise, and, by seizing" hold of one
end of the gold rod with a strong pair of clamps or flat-
nosed pliers, serrated or cut like a file on the inside of the
jaws, the ^vire may be drawn steadily through the plate,
passing from the larger to the smaller holes until a wire of
the required size is obtained.
In drawing the wire, the motion should be steady and
uniform, for if drawn interruptedly or by jerks, the wire
will be marked by corresponding inec[uahties. The gold
rod should also be annealed from time to time, and the holes
kept well greased or waxed.

REFINING GOLD.
Elements Employed.—The separation of foreign metals
from gold by what is termed the " dry method " is effected
by the action on them of either oxygen, chlorin, or sulphur,
converting them into oxids, chlorids, or sulphids. Certain
compound substances are used for this purpose which, w^hen
heated and decomposed, yield these elements in sufficient
cjuantities for the purposes specified. The refining agents
in common use are potassium nitrate (niter, or saltpeter),
W'hich yields oxygen; mercuric chlorid (corrosive sub-
limate), which yields chlorin; and antimony sulphid, which
yields sulphur.
Separation of Foreign Metals from Gold.—The most
troublesome ingredients which find their way into gold
alloys are what are commonly called base metals, as tin,
lead, zinc, iron, antimony, bismuth, etc. In attempting to
separate these metals from gold, it is not a matter of indif-
ference what reagent is employed, inasmuch as distinct
affinities exist, which may be advantageously consulted.