German_Silver

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 previously heated zinc, or by heating the finely divided metals under a layer of charcoal. To destroy its crystalline structure and so render 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 oxidation unless protected from the atmosphere. At a heat above dull redness it becomes exceedingly brittle. German silver in various modifications of composition is much used in the arts. Alloys, of which about 50% 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 suitable for rolling and for wire. In Chinese white silver or packfong (paktong) the amount of copper is smaller, about 40%, 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 resistance and a low temperature coefficient, has been used for electrical 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.

* * *