platinite,alloy that is 46% nickel and 54% iron. It is used in the manufacture of electric lightbulbs because its coefficient of expansion, i.e., the rate at which its volume increases with temperature, is the same as that of glass.
a bimetallic wire consisting of an iron-nickel core (58 percent Fe, 42 percent Ni) with a thin coating of copper (about 30 percent of the total weight of the wire).
Platinite has a coefficient of thermal expansion close to that of platinum (about 9 × 10 –6 deg–1) and is used to replace platinum in leads in light bulbs and various vacuum-tube devices to provide a hermetic seal with glass. An iron-nickel alloy containing 54 percent Fe and 46 percent Ni, which is used for junctions with ceramics (Soviet brand 46N alloy), is sometimes also called platinite.