Details of the latest developments are under lock & key, but World War II has been the making of indium: Indium is a once-rare metal that even in very small quantities makes soft metals hard, dull ones bright, and does many an odd job in stretching the supply of critical materials. It is silver white, malleable, ductile, soft, more than twice as heavy as iron, lighter than lead.
Although it was discovered in 1863, indium was strictly a laboratory curiosity until Dr. William S. Murray, now of Indium Corporation of America, went to work on it in 1924. At that time only one gram was available and it was worth considerably more than platinum. Dr. Murray found that indium could be extracted commercially from a zinc ore mined near Kingman, Ariz. Last year the potential supply was figured at more than two million grams (4,400 Ib.) annually, at a cost of about 40¢ an ounce. At the rate that it is being put to work, much of that will be needed soon.
Some new uses of indium:
> In aviation and diesel engines, copper-lead and cadmium bearings with indium added are proving extra strong and highly resistant to acid corrosion of lubricating oil.
> A 60% silver-40% indium alloy has the same appearance as sterling but is more than three times as hard—a great advantage in the many industrial uses planned for silver.
> Dental alloys of gold and indium stand up well under molar pressure and the tarnishing action of acids.
> Reflectors for searchlights, headlights, etc. made with indium alloys are not quite as bright as those made with silver and certain other materials, but they retain a uniform value for much longer periods.
> As a substitute for chromium and nickel plating, indium takes a high polish, is resistant to discoloration. Deposited electrolytically, it diffuses with underlying non-ferrous metals to form a protective coating.
> Indium, mixed with copper-base brazing materials in varying quantities, makes possible a wide range of melting points.
> Still in the experimental stage are medicinal applications of indium and its use in a new mordant (color fixer) for the dyestuff industry.