IGNITION, FLAME, EXPLOSION

IGNITION, FLAME, EXPLOSION

In a recent address on the subject of “Ignition, Flame, Explosion,” Dr. J. A. Fowler, editor of the American Exchange and Review, pointed out that, while every class of property has its fire outbreak and flammation according to its kind, occurrence of ignition is affected by extraneous circumstances. “In thermotics, the science of heat, heat is styled ‘a mode of motion,’ and every atom in the universe is in eternal motion. This is to say that heat is a force, and that degree of heat means the velocity of the force-action. Substance or matter is an aggregate of atoms—that is, ultimate particles (ultimate to our conception)— and such particles in association by attraction are called molecules. Heat being a mode of motion, the question arises, What is in motion? The answer is, certain designations called chemical elements, and these are, first, the inflammables: Hydrogen, carbon, potassium, sulphur, calcium, chlorine, phosphorus, sodium. Atoms of these move towards each other up to contact by affinity, or away from each other by repulsion. Then comes oxygen as a predominant firer, and called a supporter of combustion, and combustion then means, or about means, the union of oxygen with an inflammable, yet the rusting of iron in the formation of a peroxide is also a combustion. * * * While the heating of a body expands it, in chemical theory, when atoms combine under chemical affinity, such combining makes combustion, and that does not start with molecular dissociation. Dissociation is the production by the action of heat on a body attributed to a ‘force called the repulsive force of heat. By selecting a proper compound and heating it sufficiently, the distance between the molecules can be increased to such an extent that they will separate into their elementary condition—self-caused spontaneous decomposition not determined by any chemical action, or the dissociation of compound bodies.” Heat is of mechanical or dynamic production as well as chemical production. In the case of a recent blazing on a steamer arising from a keg of chlorate of potash-chlorine and potassium—the question was, whether the fire was caused by the keg with its contents falling upon the deck, or was due to a lighted cigarette. This chlorate, which is much used in the manufacture of fireworks and matches, is explosive by friction, but, as explosion is instantaneous combustion, when not mechanical, and the chlorate burst into flames, it was manifestly not due to friction, and, when not mixed with such combustibles as sulphur and charcoal (a carbon), it is rather flammable than explosive. Water dripping on lime (oxide of calcium) dissociates the oxygen and hydrogen. A compound of the two is formed hy the lime burning—that is, oxygenation is a reconstruction. Spontaneous ignition may be a hydro-oxygenation, or the oxygenation resulting from dry confined air. Temperature of heaps of rags, tow, and compact sawdust, which are greasy, may rise through the absence of ventilation. Fires in wellfilled and long-locked closets start through condensation of oxygen. In the centre of a bale of cotton the condensed oxygen may make heat, which will make flame when a further supply of oxygen is admitted by opening the bale. In this case, however, pressure, by itself, may be a factor of the heating. As Nature is mathematical, when the oxygen of carbon proceeds to the monoxide degree tone atom of oxygen), it burns with a lambent blue flame; when it reaches the dioxide degree (carbonic acid), it is not only non-inflammable, but is an extinguisher of flame. A feeble supporter of ordinary combustion is chlorine, but the heat evolved during the combination of chlorine with hydrogen exceeds that produced by a mixture of oxygen and hydrogen, and the former ignities at a low temperature. Passing over the heat effect of sulphur combinations, it is to be said that carbon, hydrogen, and oxygen produce ninety-five per cent, of the flame risk of the United States. Preceding ignition are latent heat and radiant heat. Resistance to radiation makes heat, as resistance to the electric current makes flame-flash. Nitrogen may be named a supporter of explosion by resistance to flame. At about 200 degrees Fahr. of heat chloride of nitrogen explodes with great violence; dynamically, it explodes with the touch of a feather or by dropping into water Sodium may be considered more of an explosive by heat than a flammable. Dr. Fowler recalled a file in Philadelphia which burned over eighteen acres of non-congested district, and with but slight exposurehazard. The fire reached a warehouse in which saltpetre—a nitrate of potassium—was stored.. On the water reaching it, two explosions took place, the second rending everything in sight. The fire kept spreading for twelve hours, when the heightening temperature of the air caused the denser outer air to press inward upon the heat-rarified air, and the flames were driven back upon themselves. Saltpetre explodes only “under special and very limited conditions. When the potassium, or, rather, potassious product of nitre—burning with carbonaceous material in a confined space—is heated to a white heat, explosion is produced by contact with water— the violence of the explosion somewhat dependent upon the temperature of the water. With carbon, hydrogen, and oxygen, the main elements of property fire risk, texture of combination makes degree of risk. Wood, as timber, is more or less than fortynine per cent, carbon, forty-five per cent, oxygen, and six per cent, hydrogen, and, with their relative hardness, white pine has nearly three times the flammability of hickory. If there is a pile of pine wood boards, and a lighted match is applied to them, flame is about an impossibility. If a part of the boards is reduced to shavings, and the lighted match applied to a pile of them, name will result. If the granulation of lumber in a sawmill could be equal to pulverisation, the comminuted grain, if sufficiently light to float in the air in due proportion, would become an explosion at touch of flame; but, as the sawing is inadequate, the explosibility is deferred to grinding, as in the case of dust-explosion in flour and grist mills, when the explosive dust comes from smut cleaning, and middlings purifier machines. We say that flame is light and heat. Intensity of heat is greatest in hydrogen, which is fourteen and onehalf times lighter than air, and is of low luminosity. Carbon is the great illuminator. So, in a hydrocarbon flame, for giving light below the carbon burning, is a non-luminous flame. As movement of flame is predominantly vertical, though expanding laterally, such movement is a determining factor in fire hazard. It augments the risk in the occupancy in which a fire starts, but diminishes it as a communicator or exposing flamer. It makes ignition in the fourth story of a six-story building a less burner than ignition in the basement. It has been said that a volume of flame of 216,000 cubic feet cannot be extinguished by any fire department on the globe, so it must simply burn itself out. But, with like material of building and contents, and forty feet height of building, the 216,000 cubic feet, as 40X75X72, is one-third less fire risk, and as much less difficulty of extinguishment. In the former case the area is 3,600 square feet; in the latter, 5,400 square feet.” Dr. Fowler then pointed out that “while the three-heat phenonmena noted may be taken as denoting ‘fire,’ comprehensively, in the insurance sense, they denote but part of the caloric manifestation, as even the deflection of an iron column from its vertical supporting capacity by heat is an insurance hazard.” He, therefore, drew a “dividing line between ignition flame, explosion and incandescence, fusion, disintegration, and refraction, as the latter constitute only a minor department of insurance thermotics. When bodies heated to luminousness with limited radiation retain their solid or liquid form, it is named incandescence. Extending luminosity to illumination, in electric illumination the light is of two kinds—the arc light and the incandescent light. In the first, a voltaic arc is employed; in the second, a resisting conductor is rendered incandescent by the current. Fusion is the liquefaction of a solid body by means of heat. Disintegration is the disruption, not the liquefaction of a solid body by means of heat. When the heat cannot effect incandenscence or fusion or disintegration any more than flammation, the substance attacked is refractory. Years ago firemen said “that granite could not stand fire,” and lithologists say that, owing to the unequal expansion of its parts, granite cracks, and sometimes explodes by the action of fire. Here the exploding means the detonation of mechanical disruption or dissociation. In a general way, it may be said that somewhere about eighty per cent, of the subjects of heat are affected as to heating by relative weight—that is, the lighter the weight, the more heatable. So. with iron weighing per cubic inch .280 of a pound, and hard wood weighing .048 of a pound per cubic inch, the iron fuses at 1.538 degrees Fahr. and the wood will flame at about 600 degrees Fahr.; but then, otherwise, clay, weighing .068 of a pound per cubic inch is refractory as to heat, and, popularly speaking, we may say that manufactured products of clay are non-burnable. Taking the following weights per cubic foot: Marble, 170 pounds, cast iron, 450 pounds, and steel. 490 pounds, while the stone disintegrates and the metal fuses, it can be said that the marble is 190 per cent, more affected by fire than the steel is.

A new waterworks system is being installed at Wellington, Ohio.

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