This metal presents a remarkable combination of qualities. It is the lightest of the useful metals (excepting magnesium, which has only limited uses as a metal), has many exceptional uses, is more abundant in nature than any other known metal, and is extracted by a process quite apart from general metal extraction methods.

Its physical qualities are as follows:

Color, silvery white.

Malleability and ductility, slightly less than that of copper.

Tensile strength, varying from about 16,000 lbs. for cast metal to about 25,000 lbs. for rolled metal. Annealing slightly decreases the strength of rolled metal.

Fusing point, about 1200° F.

Specific gravity, about 2.6, or about 1/3 the weight of iron.

It is an excellent conductor of heat and electricity, does not corrode in air or in water to a noticeable degree, but it can be soldered only with much difficulty due to the fact that the pure metallic surface quickly unites with oxygen, forming a film on which the solder will not hold.

Aluminum is not so soft as copper, and when hammered assumes the hardness of hard brass, although annealing (heating to a red heat and cooling slowly) again renders it pliable.

In melting it for castings, an ordinary crucible should be used, but flux should not be used because of the chemical combination likely to result. It shrinks much on cooling.