Phosphorus was originally discovered in 1669 by Brandt, a Hamburg chemist, who .obtained it from urine. Galin and Scheele were, however, the first to discover its pres ence in bone, and to employ that material for its preparation. The following arc the leading steps of the method now usually employed in obtaining it on the large scale. Bones are burned to whiteness, and powdered; and this bone-ash is then mixed with sul acid in such quantity as-partially to decompose the phosphate of lime occurring the ash into insoluble sulphate of lime, and a soluble superphosphate of lime, whose composition is represented by the formula The solution of the superphosphate is evaporated to a syrup, mixed with charcoal, and submitted to dis tillation in an earthen retort exposed to a red heat. Phosphorus rises in vapor, and is conveyed, by means of a bent tube, into water, in which it condenses in yellow drops. Two distinct processes take place within the retort. The first consists in the decomposi tion of the superphosphate of lime into bone-eatth and hydrated phosphoric acid; while the second consists in the deoxidation, by means of the carbon, of the liberated phos phoric acid into phosphorus—a process accompanied by the evolution of hydrogen :111(1 carbonic oxide 7nses. After it has been prs.Q2ed M a fused state through wash-leather, and further purified, it is forced into tubes, in which it is allowed to solidify, and which give it the form of sticks, in which it is commonly met with.
Phosphorus forms with oxygen an oxide, Which is always produced in small quantity when phosphorus is burned in air, but is of Do practical importance), and three eids—viz., hypophosphorous acid, P0, phosphorous acid, and phosphoric acid, PO6. Of these compounds, phosphene acid is by far the most important, and we shall therefore consider it first in order of the three acids.
Phosphoric acid in its anhydrous state, or phosphoric anhydride, as it is usually termed nt the present day, is represented by the formula and is obtained by burning phos phorus in a jar of perfectly dry atmospheric air or oxygen. when it is deposited in snow white flakes at the bottom and on the sides of the jar, from whence it must be removed by means of a platinum spatula as quickly as possible, in consquence of its attracting moisture from the atmosphere, and placed in a perfectly dry flask. When dropped into water, it combines AVitli it, and dissolves, evolving a considerable amount of heat, and emitting a hissing sound, as when red-hot iron and water come together. In conse quence its strong affinity for water, this anhydride is very useful in the laboratory as ,desi mat ng agent.
There are three hydrates of phosphoric acid, each of which possesses the properties of .141istinet acid—viz , a protohydrate (I10,P06), a deutohydrate and a hydrate (3IIO.P0,,). These hydrates retain theircharacteristic properties when dissolved in -water, and combine AN ith one, two, or three equivalents of bases to form salts, accord to the hydrate employed. In the salts formed by the first hydrate, the one equiva lent of water is replaced by one equivalent of base; in those formed by the second hydrate, both equivalents of water may be replaced by two of base, or one equivalent of water alone may be replaced, while.the other remains in the salt as basic water; while is those formed by the third hydrate, all three equivalents of water, or two, or only may he replaced by base, so that this acid forms three sets of salts. Hence phosphoricc acid is what is termed a polybasic acid ,q.v.). The scheme may elucidate this remark: if M,'M', M', are any three metals, whose oxides net as bases, the mono hydrate forms the salt and is mono-basic; the dentohydrate 2110,P01 forms the salts M0,M'O,PO6 and and is bibasic; the tritobydrate 3110,P0p forms the salts 310,111'0,M"0,P02, and M0,2110, PO., and is tribasic.
The occurrence of phosphoric acid in a state of combination) in the three kingdoms of nature has been already noticed in our remarks on phosphorus. The discovery of the
acid was made in 1740 by Marggraf; the discovery of its true chemical nature is, how ever, due to Lavoisier-f and that of its various modifications and its polybasMity, to the investigations of our illustrious countryman, Graham.
Phosphorous acid occurs both as an anhydride, PO., and as a hydrate, 3110,P03. Hypophosphorous acid (3110,P0) is only known in its hydrated condition, in which it occurs as a very acid, colorless, uncrystallizable syrup.
Phosphorus combines with hydrogen in three proportions to form phosphuretcd hydrogen gas, PH.; liquid phosphide of hydrogen, and solid phosphide of hydrogen, P.H. Of these, the first alone requires notice in these pages. There are various processes for obtaining the gas; one of the simplest being by boiling fragments of phosphorus in a concentrated solution of hydrated potash, in which case, hypophosphite of potash is formed, while phosphureted hydrogen as is extricated. The reaction is explained by the equation, 4P+ 3(110,K0)= 3(K0,P0)+P11.. The gas thus evolved is colorless, possesses a characteristic fetid odor, and has the remarkable property of tak ing fire spontaneously in atmospheric air or in oxygen gas, and of resolving itself into anhy drous phosphoric acid, and water—a phenomenon • of which prof. Miller, has given the following graphic description " If allowed to escape into the air in bubbles each bubble as it breaks produces a beautiful white wreath of phosphoric acid, composed of a number of ringlets' revolving in vertical planes around the axis of the wreath itself as it ascends; thus tracing before the eyes, with admirable distinctness, the rapid gyratory movements communicated to the superincumbent air by the bursting of a bubble upon the surface of a still sheet of water. If the bubbles be allowed to rise into a jar of oxygen, a brilliant flash of light, attended with a plight concussion, accompanies the bursting of each bub ble." There is reason to believe that perfectly pure phosphureted hydrogen gas does not possess the power of igniting spontaneously, and that the self-lighting gas always con tains a minute quantity of the vapor of the liquid phosphide The luminous phenomenon known as will-o'-the-wisp has been referred to the natural evolution of the gas; there is, however, no scientific evidence in favor offthis hypothesis. .
Various compounds of phosphorus with sulphur, chlorine, iodine, bromine, etc., have been formed and investigated; but none of them are of any practical importance.
The medicinal uses of phosphorus and phosphoric acid have still to be considered. Phosphorus, dissolved in ether or oil, was formerly prescribed in very minute doses as a stimulant to the nervous system in certain conditions. It is, however, now rarely employed in medicine, at all events, in this country, in consequence of its poisonous properties. Several cases are on record in which children have been killed by sucking the phosphoric ends of lucifer-matches: and Christison relates an instance in which a grain and a half of phosphorus proved fatal.
The symptoms induced by this poison are those of acute inflammation of the stomach and bowels, and the only treatment that can be recommended is the administration of large quantities of mild demulcent fluids, such as milk and thin arrowroot, so as, if possible, to envelop the phosphorus, and exclude it from the action of the air hi the intes tinal canal; and of magnesia, with the view of neutralizing any phosporous and phos phoric acids that may be formed.
Dilute phosphoric acid is included in the British pharmacopceia, but is not very much employed. It may be prescribed in much the same cases as those in which sulphuric and nitric acids are employed, and is less likely to disturb the digestive functions, if employed for a long period, than the other mineral acids. The late Dr. Paris used to recommend it, when properly diluted, as the b8st acidulated drink for assuaging the thirst in diabetes. It may be prescribed in half-dram doses.