GERMAN SILVER or NICKEL SILVER, an alloy of copper, nickel and zinc, prepared either by melting the copper and nickel together in a crucible, and adding piece by piece the previ ously heated zinc, or by heating the finely divided metals under a layer of charcoal. To destroy its crystalline structure and so ren der it fit for working it is heated to dull redness and then allowed to cool. German silver is harder than silver; it resembles that metal in colour, but is of a greyer tinge. Exposed to the air it tarnishes slightly yellow, and with vinegar affords a crust of verdigris. At a bright red heat it melts, losing its zinc by oxida tion unless protected from the atmosphere. At a heat above dull redness it becomes exceedingly brittle.
used in the arts. Alloys, of which about 5o% is copper and the residue zinc and nickel in about equal proportions, take a fine polish and are used as imitation silver for knives and forks. With a somewhat higher proportion of copper an alloy is formed suit able for rolling and for wire. In Chinese white silver or pack f ong (paktong) the amount of copper is smaller, about 4o%, with about 32% of nickel, 25 of zinc, and 2 or 3 of iron. German silver for casting contains 2 or 3% of lead, which like iron increases the whiteness of the alloy. German silver, having a high specific re sistance and a low temperature coefficient, has been used for elec trical resistance coils, and these qualities are possessed in a still greater degree in manganin, which contains manganese in place of zinc, its composition being 84% of copper, 12 of manganese and 4 of nickel. The addition of a trace of tungsten to German silver, as in platinoid, also largely increases the resistance.
