Chemistry in the Industries 273
is the most useful metal. More material has been taken out
of the Mesabi Iron Range than was moved in the digging of
the Panama Canal. And yet there is sufficient ore to last for
hundreds of years. In the case of iron, the first industrial
development came with the discovery that ordinary iron
could be turned into strong versatile steel through the use of
carbon. Even the ancient sword-makers, who pounded out
the famed blades of Damascus, knew the magical power of
carbon and the correlated methods of heat treatment. Nitro-
gen compounds, taken from interesting sources, were used in
the quenching bath. Today tank armor is “nitrated” in hot
ammonia gas, and the surface is thus “case-hardened.”
Steel is challenging the light metals. Low alloy steels and
new modifications of the higher alloy steels, fresh from the
laboratory, are bidding for expanding uses. These new alloys
are three times the weight of aluminum and almost five times
the weight of magnesium, but their tensile strength ap-
proximates 190,000 pounds per square inch. This advantage
permits weight to be shed by reducing bulk and eliminating
needless supports. The alloys are less subject to corrosion
than plain steel. Putting wings on freight cars is just about
what American industry is now doing—building air freighters
of tremendous proportions to carry carloads of supplies to our
nation’s forces in the far corners of the world. Many months
ago, plans were put into execution for the construction of
giant all-stainless steel cargo planes—planes that would have
the strength and stamina to withstand the vibrations and
stresses encountered under severe flying conditions.
Precise knowledge of exactly what happens in steel forma-
tion has made possible a great variety of alloy steels with
definite characteristics. Chromium, the element which im-
parts precious color to rubies, imparts something more
precious to steel. It gives steel incredible hardness and re-