Chapter XXII: Phosphorus

Phosphorus is a most interesting chemical element. This is because of its exceptional chemical properties, the very important part it plays in the chemistry of animal and vegetable life, and its employment in the friction match, one of the most convenient and useful articles of human invention.

Phosphorus appears to have been first prepared in the year 1669 by a Hamburg merchant named Brandt who became fascinated with the study of alchemy and pursued his experiments with the view of repairing his broken fortunes by the discovery of the philosopher’s stone. The happy discovery of phosphorus, while it did not enrich him, at least preserved his name in the annals of chemistry. Brandt produced it by a laborious process from certain animal matters. Notwithstanding the remarkable properties of the substance and the extraordinarily useful purposes to which modern scientific knowledge has applied it and its compounds, phosphorus remained the merest toy for more than a hundred years. In 1771 Scheele revealed to the world the fact that it may be prepared from bone-ashes, that is from burnt bone, and this has ever since been found to be its most convenient source.

The name phosphorus is derived from two Greek words (φῶς _phos_, light, and, φέρω _phero_, I bear) which suggest one of its marked properties, namely its power of continually affording light even though not set on fire after the manner of ordinary illuminating materials. It is true the light is feeble and chiefly noticeable in the dark. It is the same, in fact, as that yielded in the dark by an ordinary friction match when it is gently rubbed, but has not yet taken fire. This light, however, is the product of a true combustion, only of a very slow one; and again this burning of phosphorus is initiated by heat, (though only a very moderate amount is required for it). Of course for phosphorus much less heat is demanded than to set on fire our ordinary combustibles.

Phosphorus, though very widely distributed in nature, is never found free or uncombined. This fact is distinctly referable to the ease with which the substance combines with oxygen; if it were found free at any point on the surface of the earth, where it suffered exposure to atmospheric air, it would of course quickly enter into combination with oxygen.

Phosphorus exists occasionally in the earth in the state of combination in very hard rocky masses, of which the mineral known as apatite—composed mainly of calcic phosphate—is a good example. It is also present in small quantities in almost all soils; and in minute quantities in most natural waters, like river-water and sea-water.

One of the most familiar substances containing phosphorus is the bony skeleton of the higher animals. Here also it exists as calcic phosphate. It exists also in the brain, though in a form of chemical combination not easily stated.

Further, it is a constituent of various portions of the vegetable structure, especially of seeds.

The statements in the last two paragraphs have been presented with the express purpose of calling attention to the important offices of phosphorus in connection with animal and vegetable life. Thus exact experiments have shown that plants cannot flourish in soils barren of phosphates, and that the mere addition of almost any soluble phosphate to an arid soil promptly stimulates the plant living upon it, into more luxuriant growth. These facts have led to the introduction into commerce of artificial fertilizers containing soluble phosphates as their principal ingredients; and the manufacture of such fertilizers has continually expanded, until now it is conducted by the principal commercial nations on a truly gigantic scale. For the purpose of this manufacture, _bones_ are particularly favorable because of their porosity. In fact the surface of the world is ransacked to supply this raw material. Thus from the deserts of Africa, bones are conveyed as far as England to be manufactured into fertilizers; and so from the great western plains of the United States, bones are brought to the eastern centres for a like use.

The agricultural demand for phosphates of some sort has become so imperious that even apatite is now largely used, notwithstanding the difficulties that its exceedingly hard and compact structure place in the way of the manufacturer.

From the plant, phosphorus finds its way in the form of food into the animal system. The living animal appreciates this essential ingredient, carefully selects it out from the food, and stores it up both in its brain and in its bony framework. This framework is exceedingly important as giving the requisite rigidity to the whole structure, and the proper support for the action of the various muscles.

Phosphorus itself is prepared by a process too complicated for the ordinary amateur chemist to repeat; indeed its preparation, even on the large scale, presents serious difficulties. These are associated with the great combustibility of the substance, which makes necessary extraordinary precautions against fire. Again, laborers in phosphorus works are subject to a painful and incurable disease called _phosphorus necrosis_, which has a peculiar and destructive effect upon the bones of the jaw. Finally, the chemical changes involved give rise to such difficulties and complexities as force the manufacturer to unusual watchfulness. In fact it has been recently stated that there are scarcely more than two factories for phosphorus manufacture in the world—one in England and one in France.

The element phosphorus, as ordinarily seen, has much the appearance of wax. It has a white or amber color, and is translucent; it may be cut with a knife much as wax cuts. It is ordinarily sold in the form of cylinders of about half-an-inch in diameter. It is necessary to keep it in vessels of water, for as already stated, if exposed to the air it would oxidize. This oxidation, at first slow, increases in vigor from the heat afforded by the earlier stages. After a short exposure to air, portions of phosphorus spontaneously burst into flame. Evidently then, phosphorus should not be handled except under water. Cases are recorded of severe and even fatal burns—the result of handling phosphorus in the air.

We may with propriety call attention here to another peculiarity of phosphorus, which constitutes one of the remarkable features of this interesting element. About thirty years ago, a Vienna chemist discovered that when phosphorus is heated for a considerable length of time, under conditions such that no gas is present which can act chemically upon it, it undergoes a marked change in its properties. Thus its color turns to red, and, strange to say, it loses altogether that ready combustibility which is the most striking characteristic of ordinary phosphorus. It may seem incredible that any such change could in fact occur. But this red phosphorus has become an article of considerable importance in commerce, and it is a well-established fact that ordinary phosphorus may be turned into this modification without any gain or loss of weight, and that, on the other hand, this red phosphorus may be turned back again, by suitable processes, to the ordinary form, also without gain or loss of weight. Phosphorus is not the only elementary substance that is capable of this kind of change. Indeed the general term _allotropism_ has been applied to the tendency of elementary substances to undergo internal changes, by reason of which their chemical properties are temporarily modified without gain or loss of weight, and therefore independently of chemical combination or decomposition.

Chemical Properties of Phosphorus.

The chemical properties of phosphorus are wide in their range; that is, it combines with many of the chemical elements. Thus it unites with hydrogen in more than one proportion, and thereby forms several compounds. As might be expected, they are all exceedingly combustible; one of them in particular, called phosphuretted hydrogen, takes fire at ordinary temperatures immediately upon coming in contact with the atmosphere. Its production affords opportunity for a beautiful experiment, though a somewhat dangerous one. When the gas is produced in a retort, it may be made to bubble through water in the form of vapor in company with various gases generated at the same time. Then, as it reaches the surface, it instantly takes fire, the phosphorus burning to a white, smoke-like substance which usually floats away in forms similar to those of smoker’s rings. The smoke consists of minute particles of a solid, called phosphorus pentoxide, and expressed by the formula P₂O₅. This is evidently the product of the combustion of that phosphorus which is a part of the inflammable gas. The shape of the rings is due to a mere mechanical circumstance and the same in effect as that afforded by the lips of the smoker while producing rings. Indeed if a paper box, having a round hole on one side, be filled with smoke of any kind, sharp blows upon the opposite side will drive out portions of the smoke in such a way as to produce similar rings. Such rings are often seen on a still day puffed out of the smokestack of a locomotive, and they are sometimes produced by the discharge of a cannon in still air. The fact is that in all these cases the portion of smoke producing a ring advances through the opening with a sudden impulse, the edge of the opening retarding those particles that pass nearest to it. Thus the delayed particles acquire a tendency backward and inward which starts them on the peculiar series of circular courses, which in the grand aggregate give rise to the rings.

As has more than once been stated, phosphorus has a marked affinity for oxygen. It burns in any vessel containing air, combining with oxygen in such a way as to readily deprive the air of the entire amount of this element contained in it.

The chemical change is represented by the following equation:

=P₄= + =5O₂= = =2P₂O₅=

One molecule of Five molecules of Two molecules of
Phosphorus, Oxygen, Phosphorus pentoxide,
124 160 284
parts by weight. parts by weight. parts by weight.
\__________________________________/ \_________________/
| |
284 284

When the operation is performed in a tall jar, the oxide of phosphorus produced falls as abundant flakes having a snow-like consistency. When these flakes are thrown upon water they chemically combine with the water, affording much heat and producing a hissing sound which is the evidence of it. The liquid now acquires a sour taste referable to the fact that phosphoric acid has been produced.

The chemical change is represented by the following equation:

=P₂O₅= + =3H₂O= = =2H₃PO₄=

One molecule of Three molecules of Two molecules of
Phosphorus pentoxide, Water, Phosphoric acid,
142 54 196
parts by weight. parts by weight. parts by weight.
\_______________________________________/ \_______________/
| |
196 196

Phosphoric acid is the starting point of an immense series of salts called phosphates. One of these, calcic phosphate, we have already referred to as existing in bones and in apatite.

Friction Matches.

The earliest method of producing flame appears to have been by the friction of pieces of dry wood in contact with dry leaves or similarly combustible substances. This method travelers have found to be still in use among tribes of a low stage of development. The next method seems to have been by the use of flint and steel and tinder. When the flint is sharply struck against the steel, it tears off minute particles of the metal, and these fragments are heated to the luminous point by the violence of the stroke; if they are made to fall upon the tinder, this easily combustible material takes fire; from its burning, a candle or lamp may be lighted. But the flint and steel and tinder must be dry and in good order to produce the best results; even then considerable skill is demanded. So it is easy to see that mankind has often preferred to _preserve a flame once lighted_, and then communicate this to another and another from time to time, rather than to go to the trouble of exciting a new combustion when fire was needed. And it is easy to appreciate the usefulness to its possessor of a flame once kindled—and the serious inconvenience resulting from its extinction. Thus we can readily comprehend how nations have adopted fire as a sacred agent, to be preserved continuously unextinguished, and to be guarded with religious care.

The flint and steel method has ample illustration as to its principle, not only in familiar cases like sparks from the horse’s hoof, but also in many processes in factories and machine shops. Here it is well known that the grindstones used for finishing articles of iron and steel send off from their work an uninterrupted current of minute chips of the hot and luminous metal.

The flint and steel method of obtaining fire held its own until about sixty years ago. In 1829 a kind of chemical match was devised, and soon after, in 1832, a true friction match containing phosphorus was brought into use. The _principles_ upon which the phosphorus match depend are but very slightly different from those involved in the use of the flint and steel. Thus in the friction match the rubbing upon the rough surface is a mechanical process which generates heat, just as any blow or any friction does. In the case in question the amount of heat is small, but it is sufficient to set on fire the small amount of phosphorus on the tip of the match; the phosphorus sets on fire the sulphur which coats over the end of the match; the sulphur in burning sets on fire the wood of the match, and here the combustion has reached a stage at which it is easily communicated to larger masses of material. In the finer kinds of wooden matches, in order to avoid the objectionable smell of the burning sulphur, this latter substance is sometimes replaced by a thin coating of wax upon the end of the stick. In this case, other chemicals are added to the tip of the match, in order to make the combustion more active.

Friction matches of the ordinary kind are now so abundant and familiar everywhere that the exceeding usefulness, convenience and importance of the match as a device or invention, is apt to be overlooked. It is not intended to dwell here upon this subject, however, for perhaps what has been said of the appliances for lighting used in the past, renders unnecessary further presentation of the principles utilized in the little tapers of to-day.

As an article of manufacture, the individual match is so small that it is not easy at first to appreciate the greatness of the commercial interest it represents. Thus it is estimated that in Europe alone fifty thousand persons are constantly employed in the manufacture of the various kinds of matches. Again, though the amount of phosphorus used in each match is very minute, its sum total is no less than a thousand tons a year. The value of the annual product of this industry is not far from fifty millions of dollars.

If there were introduced here an account describing at length the manufacture of the friction match—commencing at the beginning with the special kind of wood employed and the processes used for its subdivision into the requisite fragments, continuing even so as to explain the various contrivances for packing the finished product—that description might be of interest; but the special topic seems to be more properly the preparation and application of the material at the tip of the match. The sticks having been prepared, they are placed, by machine, in frames capable of containing large numbers of them. They are first sulphured, that is their ends are dipped in melted sulphur and it is allowed to harden upon them. For the finer grade of matches however, the sulphur must be dispensed with, and instead the sticks are dipped into melted wax.

In any case, they are next tipped with the highly inflammable material, this process being called chemicking. The inflammable paste is prepared in large quantities by mixing the proper ingredients in a kettle surrounded by boiling water. First, a solution of an appropriate gum or glue is made. When it has attained a proper consistency, the phosphorus is introduced little by little. The whole mass is then slowly but thoroughly agitated with a wooden stirrer until thephosphorus is diffused through the mass. Finally, other ingredients, such as potassic nitrate or binoxide of lead or manganese dioxide, which favor combustion, are added; and certain coloring matters, such as Prussian blue or vermilion, are introduced. Here is a German recipe for making this paste:

Gum, 16 parts.
Phosphorus, 9 parts.
Potassic nitrate, 14 parts.
Manganese dioxide, 16 parts.

As has already been intimated, all of these substances, except the phosphorus, may be replaced by others, according to the style of the article to be manufactured or the views of the maker. The process of chemicking consists in dipping the sulphured ends into the inflammable paste, which for this purpose is spread out on a stone slab. Finally, the tips are coated over with a thin varnish to protect them from absorption of moisture.

At present the manufacture of friction matches is carried on to a very large extent in Sweden, and that country, it is now stated, produces about seventy-five per cent of all the matches made in the world. In Sweden, too, are largely manufactured what are called safety matches. The safety matches are tipped with a composition of potassic chlorate, potassic dichromate, red oxide of lead, and sulphide of antimony. Under ordinary circumstances friction will not set these matches on fire. In lighting, they must be rubbed on a prepared surface which contains principally red phosphorus and sulphide of antimony. When the match is rubbed upon this surface, the potassic chlorate of the match and the red phosphorus of the friction-surface start a chemical combination which extends to the other materials on the tip of the match. Safety matches, then, involve an invention which in accomplishing its purpose, affords a twofold advantage. In the first place, as the match lights only on the prepared surface, the danger of conflagrations from accidental ignition of them is very largely reduced. This costly feature of the ordinary phosphorus match would be largely, if not entirely, done away with by the general use of the safety match. In the second place, the use of _red phosphorus_ has the advantage of saving human lives in other ways. Thus it spares the operatives, employed in this business, the liability to the phosphorus disease already mentioned. Again, ordinary phosphorus is very poisonous; in fact the tips of matches containing this substance have not only often produced the death of children who have tasted them, but such matches have often been used in cases of intentional suicide. Of course as safety matches contain no phosphorus, these forms of poisoning cannot arise from them.

A flame of fire, as a visible and tangible thing, has in all ages been accepted as a symbol which appropriately typifies enlightenment of the mind and soul. This favorite and beautiful figure loses none of its fitness when narrowed in its application to the aspects of these subjects in their peculiarly modern forms. For in the friction match, whose cheapness brings it to the hand of every human being however low his degree, we may discover the type of that opportunity for enlightenment offered to individuals whose circumstances seem most humble and even forbidding. The one is the invention of modern science; the other the gift of modern laws, of modern theories of the rights of men, of modern schools, libraries, and newspapers, of the modern printing press, telegraph, and railroad.

READING REFERENCE.

Friction Matches.
=Schrötter=, A. V.—Chem. News. xxxvi, 207, 219, 259.