Its electrical
resistance is half that of iron and its tensile strength is a third
greater than the strongest steel. It can be worked into wire .0002 of an
inch in diameter, almost too thin to be seen, but as strong as copper
wire ten times the size.
The tungsten wires in the electric lamps are about .03 of an inch in
diameter, and they give three times the light for the same consumption
of electricity as the old carbon filament. The American manufacturers of
the tungsten bulb have very appropriately named their lamp "Mazda" after
the light god of the Zoroastrians. To get the tungsten into wire form
was a problem that long baffled the inventors of the world, for it was
too refractory to be melted in mass and too brittle to be drawn. Dr.
W.D. Coolidge succeeded in accomplishing the feat in 1912 by reducing
the tungstic acid by hydrogen and molding the metallic powder into a bar
by pressure. This is raised to a white heat in the electric furnace,
taken out and rolled down, and the process repeated some fifty times,
until the wire is small enough so it can be drawn at a red heat through
diamond dies of successively smaller apertures.
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