The name phosphorus (light-bearer) was formerly used to designate all substances which possess the property of emitting light without at the same time having a correspondingly high temperature. The name phosphorescence, used in physics for the after luminescence shown by certain substances after a previous exposure to light, is a relic of that usage. At the present day, the name phosphorus is confined to one element, which also exhibits the above property of cold luminescence, although for a different reason.
Phosphorus was discovered about the year 1670 by an alchemist Brandt, who obtained it by the distillation of the residue left on the evaporation of human urine. He kept his method secret, but it was soon found out by Kunkel in Germany, and Boyle in England. Gahn and Scheele also soon found that the bones of the vertebrate animals were a much richer source of phosphorus, and at the present day it is still chiefly prepared from these.
The method of obtaining phosphorus depends on the fact that the oxygen compound of phosphorus, phosphoric acid, which is contained in the bones, is reduced by charcoal. The charcoal combines with the oxygen, and the phosphorus is set free and distils over.
In nature, phosphorus occurs only in the form of salts of the just- mentioned phosphoric acid. These compounds are very wide-spread, although they do not occur anywhere in large quantities. They are of great importance for organic life, since the " protoplasm " of the cells, the substance to which the actual vital activity is attached, always contains small amounts of phosphorus compounds. The nerve and brain substances, more especially, are comparatively rich in phosphorus, which is there present in the form of phosphoric acid derivatives.
Salts of phosphoric acid or the phosphates are also indispensable for the growth of plants. As the soil does not usually contain much of it, this substance is, for the purpose of high cultivation, added to the soil.
The artificial manures containing phosphoric acid play a very important role in agriculture. |