POTASH AND PHOSPHORUS

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CHAPTER VI. 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 [31]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 [32]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 [33]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 [34]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.”

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