POTASH AND PHOSPHORUS
“Let us burn a plant, no matter what kind. The first effect of the heat
is to produce carbon, which, mixed with other substances, constituted
the plant. If combustion continues, this carbon is dissipated in the
air in the form of carbonic acid gas, and there remains an earthy
residue which we call ashes. Here then are two kinds of material,
carbon and ashes, which without exception enter into all plant-life.
The plant did not create them, did not make them out of nothing, since
it is impossible to obtain something from nothing. It must, then, have
derived them from some source. We shall take up before long the subject
of coal and its origin, and shall find that it comes chiefly from the
atmosphere, whence the leaves obtain carbonic acid gas, which they
decompose under the action of the sun’s rays, retaining the carbon and
throwing off the air in a condition fit for breathing. The vegetation
of the entire earth thus finds its principal nutriment in the
atmosphere, an inexhaustible and increasingly abundant reservoir,
because the respiration of animals, putrefaction, and combustion are
continually giving forth as much carbonic acid gas as the combined
plant-life of the earth can consume. To maintain the fertility of his
fields, therefore, the farmer need not give a thought to the subject of
carbon; with no assistance from him his growing crops find in the air
all the carbonic acid gas they require. There remains for our
consideration, then, the residue left after combustion, the ashes in
fact, a mixture of various substances of which we will now examine the
most important.
“Let us put a few handfuls of ashes to boil in a pot of water. After
boiling a little while we will let the contents cool. The ashes settle
to the bottom and the liquid at the top becomes clear. Well, we shall
find this liquid emitting a peculiar odor, exactly like that which
comes from the lye obtained by passing water through a barrel of ashes.
We shall also find that it has an acrid, almost burning taste. This
smell of lye, this acrid taste were not in the water at first; they
come from the ashes, which have yielded a certain constituent to the
water.
“Hence we see that ashes must contain at least two substances of
different kinds, of which the principal one cannot dissolve in water,
but settles at the bottom as an earthy deposit, while the other,
forming but a very small part of the whole, dissolves easily in water
and gives it its properties, especially its odor and its acrid taste.
“If we wish to obtain this latter element by itself, we can very easily
do so. All that is necessary is to put the clear liquid into a pot over
the fire and boil it until all the water has evaporated. There will be
left a very small quantity of whitish matter resembling table salt. But
despite its appearance it is not table salt by any means; far from it,
as we shall quickly discover from its unbearable taste. It is known as
potash, and it is what makes lye so good for cleaning linen.
Furthermore, of the various components of ashes it is the one most
essential to vegetation. Every tree, every shrub, every plant, even to
the smallest blade of grass, contains a certain proportion of it,
sometimes larger, sometimes smaller, according to the kind of
plant-life, and therefore must find it in the soil in order to thrive.
Let us add that in growing plants potash is not as the action of fire
leaves it after the plants have been reduced to ashes. In nature it is
combined with other substances which free it from that burning
acridity. In the same way carbon, when combined with other elements,
loses its blackness and hardness; in fact, it is no longer common coal.
“What else is there in ashes? A short account of the matter will tell
us. In 1669 there lived in Hamburg, Germany, a learned old man named
Brandt, whose head was a little turned and who sought to turn common
metals into gold. From old iron, rusty nails, and worn-out kettles, he
hoped to produce the precious metal. But he did not succeed in his
endeavors, nor was it destined that he should succeed, for the simple
reason that the thing is impossible. Never is one metal changed into
another. When he was about at the end of his resources he took it into
his head to conceive a crowning absurdity. He imagined that in urine
would be found the ingredient capable of turning all metals into gold.
Behold him, then, boiling urine, evaporating it, and cooking the
disgusting sediment, first with this, then with that, until at last one
evening he saw something shining in his phials. It was not gold, but
something more useful: it was phosphorus, which to-day gives us fire.
Don’t make fun of old Brandt and his foolish cooking: in seeking the
impossible he made one of the most important discoveries. To him we owe
the sulphur match, that precious source of light and fire so easily and
quickly used.
“If you examine a sulphur match you will see that the inflammable tip
contains two substances: sulphur, laid on to the wood, and another
substance added to the sulphur. This last is phosphorus, colored with a
blue, red, or brown powder, according to the caprice of the
manufacturer. Phosphorus by itself is slightly yellow in color and
translucent like wax. Its name means ‘light-bearer.’ When rubbed gently
between the fingers in the dark, it does indeed give out a pale gleam.
At the same time there is a smell of garlic; it is the odor of
phosphorus. This substance is excessively inflammable: with very little
heat or with slight friction against a hard surface, it catches fire.
Hence its use in the manufacture of matches.
“Phosphorus is a horribly poisonous substance. By melting a little of
it in grease a poison can be obtained that will destroy rats and mice.
Crusts of bread are smeared with this composition and exposed in places
frequented by these animals. A nibble is enough to ensure speedy death.
Hence you perceive that because of their poisonous nature matches are
to be handled with extreme care. Contact with food might produce the
gravest consequences.”