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.
[Illustration: FIG. 58.—Coignet’s apparatus for production of red
phosphorus. Ordinary phosphorus is placed in a cast-iron vessel _c_; it
is then heated ten or twelve days, an even temperature being maintained
by the two iron jackets, one enclosing sand, the other holding fusible
alloy.]
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.
[Illustration: FIG. 59.—Phosphuretted hydrogen gas, of the
spontaneously inflammable variety, taking fire in air and forming
smoke-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.
\_______________________________________/ \_______________/
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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.
[Illustration: FIG. 60.—Pan or water-bath, for melting and mixing the
inflammable paste for match tips.]
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.