CHEMICAL FIRE-ENGINES. FIRE-PROOFING, OR MUSLIN THAT WILL NOT FLAME.
Which structure will be first extinguished?
Imagine yourself gazing at two wooden sheds, both quite filled with
combustible materials, and drenched with petroleum and tar. These are to
be fired, and then one is to be extinguished by water, and the other by
an extinctor, or chemical fire-engine.
"Ready!"
At the word, the torch is applied, and the first shed bursts into
flames. It soon blazes furiously. A man steps forward, armed with a
hand-pump, such as is used by the Metropolitan Fire-Brigade, and turns a
jet of water upon it.
Hiss! squish! A cloud of steam rises as the water dashes upon the fire,
and still the stream pours on. Now the fireman pauses to refill his pump
with water, and then again the jet plays on the burning pile.
The fire dims down to a dull red, the flames cease to shoot upward and
outward, and after about five minutes the conflagration is extinguished.
Bravo! A very smart piece of work!
But now the second shed is lighted, and blazes fast. Another man hurries
forward. He has a steel cylinder slung on his back, and in a second,
without any pumping, he directs a jet of fluid upon the fire. The
flames die down, the red gives place to blackness, and, in about half
the time taken by the other method, the extinctor has completely
quenched the fire. How is it done?
[Illustration: CHEMICAL EXTINCTOR.]
[Illustration: SECTION OF CHEMICAL FIRE-ENGINE.]
Within the steel cylinder is suspended a bottle charged with a powerful
acid, probably sulphuric acid--but the secrets of patents must not be
revealed. The bottle can be instantaneously broken by a lever or weight,
and the acid is precipitated into the cylinder, which is filled with an
alkaline fluid--perhaps a solution of carbonate of soda. The mixture of
these fluids rapidly produces large quantities of carbonic acid gas,
which is a great enemy to fire. Moreover, water absorbs the gas easily;
and when generated in the cylinder, the expansion of the gas causes a
propelling power, varying from seventy to a hundred pounds per square
inch. Consequently, a jet of water propelled by the gas shoots out a
distance varying from thirty to fifty feet; and when it reaches the
fire, the heat evaporates the water, and liberates the gas held in
solution, which chokes the fire.
This is the general principle of most chemical fire-engines. There are
several varieties; but they are, no doubt, chiefly based on the rapid
evolution of carbonic acid gas. If you find the principle difficult to
understand, imagine a soda-water bottle bursting, or the contents
spurting forth if the cork be suddenly removed, and you will not be so
surprised at the stream jetting forth from an extinctor. Soda-water is,
of course, aërated by being charged with carbonic acid gas.
These chemical extinctors are of all sizes; they range from small
bottles upward, to large double-tank machines, and drawn by horses. The
small bottles contain the necessary materials, so arranged that, when
the bottle is thrown down, the gas is generated and the fire choked.
Both Germany and the United States make large use of chemical
fire-engines, some of which are capable of giving a pressure of a
hundred and forty pounds, and perhaps more, to the square inch.
Cases filled with sulphur, saltpetre, and other chemicals are sometimes
used, which, being ignited, send forth a choking vapour, stifling all
fire in a confined space; again, other contrivances discharge ammoniacal
gases and hydrochloric acid.
Extinctors, or fire-annihilators, have been invented or introduced by
several persons. Mr. T. Phillips was responsible for one in 1849, which
generated steam and carbonic acid. Two or three persons seem to have had
a hand in an apparatus developed by Mr. W. B. Dick about twenty years
later, and patented April, 1869. This consisted of an iron cylinder
furnished with tartaric acid, bicarbonate of soda and water, and
generating the carbonic acid gas. The first inventor of this appliance
was a Dr. Carlier, who suggested it, or something like it, a few years
previously.
About the same time, Mr. James Sinclair introduced his chemical
appliance, the firm now being the Harden Star, Lewis, & Sinclair
Company. British fire-brigades would not touch the extinctors; but the
Americans seized upon them rapidly, and manufactured them largely. At
the present time, it is said that there is scarcely a fire-brigade in
the States that does not use a chemical fire-engine in some shape or
form.
In Britain, the extinctor, either as the hand-grenade bottle or portable
cylinder, which latter contains about eight gallons, is largely used by
private persons, and is kept in many large establishments. Several
provincial fire-brigades have also adopted the appliances in some form
or other; but, as a rule, the chemical fire-engine has not been used by
the public fire-brigades of the country. Perhaps one reason is, that it
is regarded as more suitable for private use, and not as superior to the
powerful steam-engines, hydrants, etc., operated so efficiently by
trained firemen.
It will be seen that the claims for chemical fire-engines are twofold in
character: first, that they themselves supply propelling power for the
fluid without pumps--a great consideration for private persons; and,
secondly, that the liquid thrown has far greater fire-quenching powers
than water.
To the first of these claims, it is possible that fire-brigades, with
their numerous hydrants and powerful steam-engines, would pay but little
regard; while as to the second claim, only accomplished chemists and
impartially-minded persons of wide and varied experience can form a
fully-reliable opinion.
At the time of the great Cripplegate fire in London, November, 1897,
Americans were very keen in their criticism, much of which was unjust
and inaccurate; but one of their points was the absence of chemical
appliances in the London Brigade.
It is, however, fairly open to argument whether the use of such
apparatus would have mended matters. Even Americans have by no means
abolished the steam fire-engine; and they have sometimes found that the
fire has obtained so firm a hold, that the best they could do was to
prevent the flames from spreading. When quantities of inflammable
substances are crowded in high and comparatively frail buildings in
narrow thoroughfares, you have all the elements of serious fires; and
when once fairly started, it remains to be proved whether a
gas-propelled and gas-laden stream would be more efficient than powerful
and copious jets of water.
The difficulty would appear to be rather that of directly and quickly
reaching the seat of the fire, than of the more or less fire-quenching
properties of rival fluids. From the evidence of Mr. John F. Dane at the
Cripplegate Fire Enquiry, we may gain some idea why the brigade dislike
the chemical fire-engine. He had been twenty-eight years in the
brigade--though he had then left the service, and was a consulting fire
engineer--but at one fire, where he had found a dense smoke, an hour was
occupied in tracing the fire to its source, it being worked upon by
hand-buckets. Had he used a chemical fire-engine, it would, no doubt,
have been played into the dense smoke, and damaged a thousand pounds'
worth of goods, while, after having exhausted the charge, they would not
have found the fire subdued. Chemical fire-engines could not be trusted
to discharge where wanted.
Many modern structures at the Cripplegate fire were comparatively frail.
Iron girders and stone were, no doubt, largely used, and you would
naturally think that iron would be fireproof; but, as a matter of fact,
iron may be worse than wood. That is, cast-iron is very liable to split,
if suddenly heated or cooled; and a jet of water playing on a hot
cast-iron girder would most likely cause it to collapse at once, and
bring down everything it supported in a terrible ruin.
The truth is, therefore, that light iron and stone structures are not
nearly so fireproof as they might appear. The difficulty of building
fireproof structures has not yet been fully solved, though many
suggestions to that end have been made. Wood soaked in a strong solution
of tungstate or silicate of soda is rendered uninflammable and nearly
incombustible. Silicate of soda is, perhaps, the best. It fuses in the
heat, and forms a glaze over the wood, preventing the oxygen in the air
from reaching it. But intense heat will overcome it. Whichcord's plan of
fire-proofing encases metal girders in blocks of fire-clay; other
systems make great use of concrete. Walls, of course, should be built of
brick or stone; while double iron doors are of great value, as in the
case of the warehouses burning at the docks on January 1st, 1866.
At the enquiry into the Cripplegate fire of 1897, Mr. Hatchett Smith,
F.R.I.B.A., declared that the well-holes or lighting-areas in the
warehouses involved, were a source of danger as constructed, and he
recommended that such lighting-areas should be confined by party walls,
and sealed with rolled plate-glass or pavement-lights. Windows facing
the street should be glazed with double sashes, and external walls
should be built with a hollow space of about two inches between them and
their plastering, with an automatic water-sprinkler at the top of the
hollow space. Such a plan of construction would, he contended, confine
the fire to the apartment in which it originated, though it would not
extinguish the fire in that room. The flooring Mr. Smith seemed to take
for granted would be of concrete and fireproof.
Among other fire precautions, the introduction of the electric light in
place of gas may operate as a valuable precautionary measure, especially
in theatres and public places; while a strong iron curtain, to be
quickly dropped down between the stage and the auditorium, is also a
most valuable precaution.
But all such measures may be largely neutralized by the inflammable
contents of the buildings. Some manufactures are remarkably dangerous in
this respect, and the extensive storage of certain goods renders even
spontaneous combustion probable. Thus, if a well-built fireproof
structure contain large quantities of combustible materials, and these
burn furiously, the heat evolved may be so great as to conquer almost
everything in the building. Indeed, the heat in huge fires is sufficient
to melt iron.
Nevertheless, the liability to fire and its destructiveness is much
decreased by wise precautionary measures in building, the idea
underlying them being that walls, floorings, doors, or what not should
be so made as to localize the fire to the apartment in which it
originated.
As with buildings, so with clothing. Here is a piece of muslin. Light
it: it will not flame; it slowly smoulders. But even as the problem of
building completely fireproof structures has not been solved, so also
the question of fireproof fabrics has not been completely answered.
Progress, however, has been made in that direction. Methods have been
adopted whereby the flaming of fabrics can be prevented, and their
burning reduced to smouldering.
A solution of tungstate of soda is, perhaps, one of the best chemicals
to use for this purpose, for it is believed not to injure the fibre; but
for articles of clothing, borax is better suited, as it does not injure
the appearance of the clothes, and it is very effectual in its
operation, though it weakens the fibre. Alum, common salt, and sulphate
of soda will also diminish or entirely prevent flaming; but they tend to
weaken the fibre.
A simple experiment illustrates the principle. Any boy who has made
fireworks, or dabbled in chemistry, knows that paper--one of the most
inflammable of substances--after being soaked in a solution of
saltpetre, will not flame, but smoulders quickly at the touch of fire;
hence the name touch-paper, which is used to ignite fireworks.
Some of these salts, then, prevent the fabric from flaming, and also
reduce the burning to slow smouldering, the explanation being apparently
this,--when the fabric is dipped in solutions of certain salts, tiny
crystals are deposited among the fibres on drying, and the
inflammability is diminished; but the effect of the salt upon the fabric
has to be considered, and some, such as sulphate of ammonia, will
decompose when the goods are ironed with a hot iron.
This necessary operation of the laundry, however, does not affect
tungstate of soda; and all the dresses of a household could be rendered
non-inflammable and largely incombustible by dipping them in a solution
of this salt. The proportions would be about one pound of the tungstate
to a couple of gallons of water. For starched goods, the best way to use
the tungstate would be to add one part of it to three parts of the
starch, and use the compound in the ordinary manner.
Various methods have been adopted for fire-proofing wood, the strong
solution of silicate of soda being one of the best. Asbestos paint is
also useful, if it does not peel off, a little trick to which it seems
addicted. By another method, the wood is soaked for three hours in a
mixture of alum, sulphate of zinc, potash, and manganic oxide, with
water and a small quantity of sulphuric acid. But while the
inflammability of wood may be removed, it is questionable if it can be
rendered entirely incombustible. In short, the problem of absolutely
preventing fires by rendering substances perfectly fireproof has yet to
be solved, if, indeed, it is capable of solution.
But if fire cannot be entirely prevented, could not some method be
devised of automatically quenching the flames directly they break forth?
Such a method would appear like the prerogative of the good genii of a
fairy fable, and beyond the reach of ordinary mortals. But science and
human ingenuity which tell so many true "fairy tales" have made some
approach to this also. The device is known popularly as "sprinklers,"
and is contrived somewhat in this way:--
Lines of water-pipes are conducted along the ceilings of the building,
and are connected with the water supply through a large tank on the
roof. To these pipes, the sprinklers are attached at distances of about
ten feet. They are, in some cases, jointed with a soft metal, which
melts at a temperature of about 160 degrees; the valve then falls, and
the water is sprayed forth into the apartment.
Other sprinklers are said to act by a thread, which, it is claimed, will
burn when the heat reaches a certain temperature and release the water.
The essential idea, therefore, is that the heat of the fire shall
automatically set free the water to quench it. Such great importance is
attached to the use of sprinklers by some insurance-offices, that they
offer a large reduction of premiums to those employing them. Again,
other sprinklers are not automatic, but require to be set in operation
by hand.
Nevertheless, in spite of all these varied precautions, it is
unfortunately a platitude to say that fires do occur; but the point to
be noted is, that but for these efforts, they would probably be greater
in number and more destructive in their results.
Even when the flames are raging in fury, much may be done by courageous
and well-trained men to preserve goods from injury; and, indeed, much is
done by a body of men whose work is perhaps too little known. They pluck
goods, as it were, out of the very jaws of the fire, and often while the
flames are burning above them. Would you like to know them, and see them
at work?
Behold, then, the black helmets and the scarlet cars of the London
Salvage Corps.