Not many years ago a college boy read
about an interesting metal called “aluminum.”
It was as strong as iron, but weighed only one third
as much, and moisture would not make it rust.
It was made of a substance called “alumina,”
and a French chemist had declared that the clay banks
were full of it; and yet it cost as much as silver.
It had been used in France for jewelry and knicknacks,
and a rattle of it had been presented to the baby
son of the Emperor of France as a great rarity.
The college boy thought by day and
dreamed by night of the metal that was everywhere,
but that might as well be nowhere, so far as getting
at it was concerned. At the age of twenty-one,
the young man graduated, but even his new diploma
could not keep his mind away from aluminum. He
borrowed the college laboratory and set to work.
For seven or eight months he tried mixing the metal
with various substances to see if it would not dissolve.
At length he tried a stone from Greenland called “cryolite,”
which had already been used for making a kind of porcelain.
The name of this stone comes from two Greek words
meaning “ice stone,” and it is so called
because it melts so easily. The young student
melted it and found that it would dissolve alumina.
Then he ran an electric current through the melted
mass, and there was a deposit of aluminum. This
young man, just out of college, had discovered a process
that resulted in reducing the cost of aluminum from
twelve dollars a pound to eighteen cents. Meanwhile
a Frenchman of the same age had been working away
by himself, and made the same discovery only two months
later.
Aluminum is now made from a mineral
called “bauxite,” found chiefly in Georgia,
Alabama, and Arkansas. Mining it is much more
agreeable than coal mining, for the work is done aboveground.
The bauxite is in beds or strata which often cover
the hills like a blanket. First of all, the mine
is “stripped,” that is, the
soil which covers the ore is removed, and
then the mining is done in great steps eight or ten
feet high, if a hill is to be worked. There is
some variety in mining bauxite, for it occurs in three
forms. First, it may be a rock, which has to
be blasted in order to loosen it. Second, it may
be in the form of gray or red clay. Third, it
occurs in round masses, sometimes no larger than peas,
and sometimes an inch in diameter. In this form
it can easily be loosened with a pickaxe, and shoveled
into cars to be carried to the mill. Bauxite
is a rather mischievous mineral and sometimes acts
as if it delighted in playing tricks upon managers
of mines. The ore may not change in the least
in its appearance, and yet it may suddenly have become
much richer or much poorer. Therefore the superintendent
has to give his ore a chemical test every little while
to make sure that all things are going on well.
This bauxite is purified, and the
result is a fine white powder, which is pure alumina,
and consists of the metal aluminum and the gas oxygen.
Cryolite is now melted by electricity. The white
powder is put into it, and dissolves just as sugar
dissolves in water. The electricity keeps on
working, and now it separates the alumina into its
two parts. The aluminum is a little heavier than
the melted cryolite, and therefore it settles and
may be drawn off at the bottom of the melting-pot.
There are a good many reasons why
aluminum is useful. As has been said it is strong
and light and does not rust in moisture. You can
beat it into sheets as thin as gold leaf, and you
can draw it into the finest wire. It is softer
than silver, and it can be punched into almost any
form. It is the most accommodating of metals.
You can hammer it in the cold until it becomes as
hard as soft iron. Then, if you need to have
it soft again, it will become so by melting. It
takes a fine polish and is not affected, as silver
is, by the fumes which are thrown off by burning coal;
and so keeps its color when silver would turn black.
Salt water does not hurt it in the least, and few of
the acids affect it. Another good quality is
that it conducts electricity excellently. It
is true that copper will do the same work with a smaller
wire; but the aluminum is much lighter and so cheap
that the larger wire of aluminum costs less than the
smaller one of copper, and its use for this purpose
is on the increase. It conducts heat as well as
silver. If you put one spoon of aluminum, one
of silver, and one that is “plated” into
a cup of hot water, the handles of the first two will
almost burn your fingers before the third is at all
uncomfortable to touch.
Aluminum is found not only in clay
and indeed in most rocks except sandstone and limestone,
but also in several of the precious stones, in the
yellow topaz, the blue sapphire and lapis-lazuli, and
the red garnet and ruby. It might look down upon
some of its metallic relatives, but it is friendly
with them all, and perfectly willing to form alloys
with most of them. A single ounce of it put into
a ton of steel as the latter is being poured out will
drive away the gases which often make little holes
in castings. Mixed with copper it makes a beautiful
bronze which has the yellow gleam of gold, but is hard
to work. When a piece of jewelry looks like gold,
but is sold at too low a price to be “real,”
it may be aluminum bronze, very pretty at first, but
before long its luster will vanish. Aluminum bronze
is not good for jewelry, but it is good for many uses,
especially for bearings in machinery. Aluminum
mixed with even a very little silver has the color
and brightness of silver. The most common alloys
with aluminum are zinc, copper, and manganese, but
in such small quantities that they do not change its
appearance.
With so many good qualities and so
few bad ones, it is small wonder that aluminum is
employed for more purposes than can be counted.
A very few years ago it was only an interesting curiosity,
but now it is one of the hardest-worked metals.
Automobiles in particular owe a great deal to its
help. When they first began to be common, in
1904-05, the engines were less powerful than they are
now made, and aluminum was largely employed in order
to lessen the weight. Before long it was in use
for carburetors, bodies, gear-boxes, fenders, hoods,
and many other parts of the machine. Makers of
electric apparatus use aluminum instead of brass.
The frames of opera glasses and of cameras are made
of it. Travelers and soldiers and campers, people
to whom every extra ounce of weight counts, are glad
enough to have dishes of aluminum. The accommodating
metal is even used for “wallpaper,” and
threads of it are combined with silk to give a specially
brilliant effect on the stage. It can be made
into a paint which will protect iron from rust; and
will make woodwork partially fireproof.
Aluminum has been gladly employed
by the manufacturers of all sorts of articles, but
nowhere has its welcome been more cordial than in the
kitchen. Any one who has ever lifted the heavy
iron kettles which were in use not so very many years
ago will realize what an improvement it is to have
kettles made of aluminum. But aluminum has other
advantages besides its lightness. If any food
containing a weak acid, like vinegar and water, is
put into a copper kettle, some of the copper dissolves
and goes into the food; acid does not affect aluminum
except to brighten it if it has been discolored by
an alkali like soda. “Tin” dishes,
so called, are only iron with a coating of tin.
The tin soon wears off, and the iron rusts; aluminum
does not rust in moisture. A strong alkali will
destroy it, but no alkali in common use in the kitchen
is strong enough to do more harm than to change the
color, and a weak acid will restore that. Enameled
ware, especially if it is white, looks dainty and
attractive; but the enamel is likely to chip off,
and, too, if the dish “boils dry,” the
food in it and the dish itself are spoiled. Aluminum
never chips, and it holds the heat in such a manner
as to make all parts of the dish equally hot.
Food, then, is not so likely to “burn down,”
but if it does, only the part that sticks will taste
scorched; and no matter how many times a dish “boils
dry,” it will never break. If you make a
dent in it, you can easily pound it back into shape
again. It is said that an aluminum teakettle
one sixteenth of an inch in diameter can be bent almost
double before it will break.
Aluminum dishes are made in two ways.
Sometimes they are cast, and sometimes they are drawn
on a machine. If one is to be smaller at the
top, as in the case of a coffeepot, it is drawn out
into a cylinder, then put on a revolving spindle.
As it whirls around, a tool is held against it wherever
it is to be made smaller, and very soon the coffeepot
is in shape. The spout is soldered on, but even
the solder is made chiefly of aluminum.
Aluminum dishes may become battered
and bruised, but they need never be thrown away.
There is an old story of some enchanted slippers which
brought misfortune to whoever owned them. The
man who possessed them tried his best to get rid of
the troublesome articles, but they always returned.
So it is with an aluminum dish. Bend it, burn
it, put acid into it, do what you will to get rid
of it, but like the slippers it remains with you.
Unlike them, however, it brings good fortune, because
it saves time and trouble and patience and money.
A few years ago the motive power for
most manufactures was steam. Electricity is rapidly
taking its place; and if aluminum was good for nothing
else save to act as a conductor of electricity in its
various applications, there would even then be a great
future before it.