CHAPTER XIII. 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?
CHEMICAL EXTINCTOR. 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.