BY PROF. J. T. EDWARDS, D.D.

Director of the Chautauqua School of Experimental Science.

CHEMISTRY OF FIRE.—ANCIENT FANCIES.

In all ages, and among all nations, fire has been regarded with peculiar interest. Of the four great elements so essential to life—earth, air, water, fire—the last has often been considered as divine in its origin and influence. To the unscientific observer it seems more than matter, and little less than spirit. Contemplating a flame, he sees that while it has form, it lacks solidity. He may pass a sword through it, but like the ghost of the story, no wound is made in its ethereal substance. Its touch is softer than down, but it penetrates the hardest substances. The diamond carves glass, but flame destroys the diamond.

Men early found that fire was directly connected with their comfort and progress, and even essential to their existence. How they first obtained it is still matter of conjecture; whether it was brought down from the skies, as the ancient Greeks supposed, struck out from the flinty rock, evolved by the friction of dry wood, kindled by the lightning, or obtained from the flaming torch of the volcano, we can not tell.

Certain it is, that having once been obtained, all the early races were very careful to preserve it. Among many it was regarded as sacred, and kept perpetually burning, both in their places of worship and in their homes. The officers appointed for its preservation were of the highest rank and influence. Among the titles assumed by Augustus CÆsar was that of keeper of the public fire. Whenever by accident the fire in the temple of Vesta, at Rome, was extinguished, all public business was at once suspended, because the connection between heaven and earth was believed to be severed, and must be restored before business could properly proceed.

Grecian colonists carried fire to their new homes from the altar of Hestia. The “Prytaneum”[1] of the ancient Greeks and Romans was a place where the national fire was kept always burning; it was here the people gathered, foreign ambassadors received, and hospitalities of the state were offered. Here, too, heads of families obtained coals for lighting their household fires, which in turn became sacred, so that every hearth was an altar, where resided the Lares and Penates, the gods who presided over the welfare of the home.

Fancies akin to these beliefs of olden time may still be found among the nations of the East and in northern Europe.

MODERN FALLACIES.

No correct ideas of combustion were attained until the time of Lavoisier.[2] This great French savant gave precision and accuracy to the investigations of chemical science by the introduction of the balance. He disproved the theory that “water is the ultimate principle of all things,” and prepared the way for a clear apprehension of the truth that matter, though constantly changing its form, is never destroyed. He also announced the correct theory of combustion. Until this time scientists had held what was called the “Phlogiston[3] Theory.” We can but smile at the absurdity of this belief, and yet no hypothesis was ever taught more positively, or maintained more tenaciously. It declared, in brief, that when substances burned, they parted with a certain material called phlogiston. When, at length, its advocates were asked to explain the fact, discovered by Dr. Priestly,[5] that quicksilver, when burned, weighed more than before, they were forced to put forward the ridiculous statement that phlogiston possessed the property of “buoyancy” so that when it was contained in a body its weight was lessened; which was as wise as the brilliant supposition that a person can lift himself over a fence by tugging at his boot straps. After a fierce struggle they were forced to confess that they had placed “the cart before the horse.” The truth was precisely opposite to their statement. Substances when they burn take up something instead of giving it off. That something is oxygen, and a body when burned, if it can be weighed, will be found to weigh as much more as the added weight of the oxygen which has united with it. Example: Iron-rust is iron, plus oxygen.

THE TRUE EXPLANATION.

We shall here confine ourselves to the consideration of the heat and light produced by chemical action. It will be remembered that by this term (chemical action) is meant the process of uniting two or more different elements to form a compound different from either. We usually consider air essential to combustion, but this is not necessarily the fact. Gold foil or powdered antimony, dropped into a jar of chlorine, spontaneously ignites. Even in the interior of the earth, heat must be produced by the uniting of any elements that have an affinity for each other.

The most common agent of combustion is oxygen. Of this interesting gas some description has been given in a preceding article. It is the fruitful source of almost all of our artificial heat.

The fallen tree in the forest is slowly consumed by it, not less surely than the flaming wood and coal in our stoves. The human body is a furnace. In the minute corpuscles[7] of the blood, carbon is uniting with oxygen as certainly as are the particles of carbon in the flame of our lamps.

Oxygen is the scavenger that partially cleans our gutters. It is a bird of prey that devours the offal in our fields and woods. It is nothing less than the gnawing tooth of old Father Time himself, which crumbles cities and destroys all things.

Combustion, as we now know it, consists simply in the union of some combustible material with oxygen. The generic term for all this action is “oxidation.” For convenience, special names are given to particular modes. When metallic oxidation occurs we call the product “rusting.” When oxygen unites with vegetable matter we call it decaying or rotting; when with animal substances we term it rotting or putrefaction. When flame is produced, the word combustion or burning is used. The amount of heat generated is, in all cases, proportioned to the amount of chemical action. Great ingenuity and skill have been shown in the discovery and utilization of materials best calculated to combine readily with oxygen. To these, as a class, has been applied the term

HYDRO-CARBONS.

All substances composed essentially of the elements, hydrogen and carbon, would come under this designation. These would include coal, wood, petroleum, the fats, resins, wax and many others, with some of the gases, among which may be named light and heavy carburetted hydrogen, CH4 and C2H4 respectively.

In the days of our grandfathers tallow candles were almost universally employed for lighting houses, and wood for warming them. It would not be impossible to find even now, in our own country, homes illuminated (?) by a rag burning in a saucer of fat. Some of us are not too young to remember the bundle of candle-rods—nice, straight sticks used in dipping candles—snugly put away for that purpose, alas! sometimes summoned forth to assist in enforcing family discipline!

Strands of twisted cotton wick were suspended from these sticks, and successively dipped into a kettle of hot tallow, until external additions made them of the requisite size. Tin candle moulds finally superseded these. Then the wick was suspended in the center and the fat poured in. In cooling, the candles contracted, and so slipped easily from the moulds. Wax candles can not be cast in moulds, as they expand in cooling. They are made by pouring successive additions upon them. They are afterward given symmetrical form by rolling and shaping. Along the sea coast I have seen women and children gathering bay berries,[10] a fruit about as large as a grain of black pepper and covered with a grayish-white, fragrant wax. When these seeds are placed in hot water the wax dissolves and serves the same purpose as tallow, making delightfully aromatic candles.

Many of the hydro-carbons possess an agreeable odor. Sometimes the woodmen gather the bark and chips of the hickory to smoke hams and shoulders on account of the peculiarly pleasant flavor they impart. In burning, a candle or lamp becomes a gas factory, manufacturing and consuming its own product. The flame consists of three cones. The first, that next to the wick, is composed solely of gas. It is not hot, as can be shown by thrusting the end of a match into it, the match will not ignite. If the match be placed across the flame at the same point it will burn at the edges, but not in the center. A more striking illustration of the fact that the flame is hot only where it comes in contact with the air, can be shown in the following manner: Place on the bottom of an inverted plate some alcohol, in the center set a tiny saucer containing powder; ignite the alcohol, and the powder will remain undisturbed in the center of the surrounding flame until a draft brings the edge of the flame against the powder, when it will at once explode.

Look steadily at the flame of an ordinary candle and you can readily discern the three cones; the first is gas, the second gas in rapid combination with the oxygen of the air, the third the products of this combination—watery vapor, carbonic anhydride, and, possibly, some unconsumed carbon.

The process that goes on in our stoves is essentially the same. The carbon and hydrogen of the wood or coal unite with the oxygen that passes through the draft. Now note a wonderful provision for our comfort. It has already been remarked that the product of combustion consists of the thing burned, plus oxygen. Suppose, in the case of our fires, this product were a solid, we should then be forced to take out of the stove more material than we put in. The Creator has, however, provided that these resulting materials shall take the form of gas or vapor, so that they can float away. The ashes that remain form but a small part of the whole. The two most common products of combustion are watery vapor and carbonic anhydride.

The illumination of our towns and cities has long been accomplished by the use of gas manufactured from coal. Bituminous coal is used for this purpose, and the process consists in heating it to destructive distillation, and afterward condensing and absorbing such portions of the volatilized materials as might clog the gas pipes or interfere with perfect combustion.

Nature, it is now known, has her own gas works, on an immense scale. Thirty-five years ago the village of Fredonia, N. Y., was partially lighted with gas, and the supply is still unexhausted. Indeed, of late, many private individuals have sunk pipes two or three hundred feet, and thus supplied their homes with gas for illuminating, heating, and cooking purposes. In Butler and McKean counties, Pennsylvania, the production of these gas wells is enormous. Many have been burning day and night for years, while others have been utilized for heating and lighting towns and cities. Gas is now extensively used in rolling mills for smelting iron. Petroleum, or rock oil, which is usually associated with this natural gas, has now become of immense value to this and other lands. It is one of the chief articles of export from this country, ranking perhaps as fourth. Wells have recently been struck in Pennsylvania that flowed 5,000 and 6,000 barrels per day.

There is reason to believe that this material is the product of distillation of organic matter in the earth. It is found in porous rock, usually coarse sand, at depths varying from three hundred to two thousand feet. When the rock above the sand containing oil is tight, the gas is often retained, which by its expansion presses upon the oil and forces it to the surface through the pipes put down for this purpose. This produces a flowing well. When the gas has escaped a pump is necessary.

The most useful hydro-carbon now employed is coal. Its use was first introduced in the latter part of the twelfth century, and as late as the thirteenth century petitions were made by residents of London demanding its exclusion, on account of its injurious effect on the health. But now, Great Britain mines annually more than one hundred million tons of coal. Its uses are manifold. By it England has multiplied her power a thousand fold. It is almost always employed in generating steam, and the aggregate steam power of England is equal to the productive laboring force of four hundred millions of men, or “twice the power of the adult working population of the globe.” Most countries know its value.

Coal is the key that unlocks for us the treasures of the iron ore. It seizes upon the oxygen in the ore, and liberates the pure metal. By a wonderful provision they often exist in the same mountain, side by side. I have seen in Pennsylvania, running out of the same tunnel in the hills, car loads of coal and iron ore.

Among the many advantages possessed by our own country is our immense store of this precious hydro-carbon. With an area of 300,000,000 miles of territory, we have more than 200,000 square miles of known coal producing area, or one in fifteen.

Great Britain has one-half of the coal fields of all Europe, but even she has but one square mile of coal to twenty square miles of territory. Beside, our coal seams are of great thickness, and lie comparatively near the surface. In the far West, vast fields of lignite[14] have been discovered, so that there seems no prospect of our exhausting our fuel supply for ages to come.

The diamond is crystallized carbon, and can be burned, though one would hardly care to be warmed by so costly a fire.

Cleopatra, in a freak of extravagance, dissolved a wonderful pearl, but who could think of the wise queen of England using in so wasteful a manner her Kohinoor.[15] Six of the great diamonds of the world are called, by way of eminence, “The Paragons,” and a romantic interest has been attached to this form of carbon among all nations. In point of fact, however, the black diamonds of the coal pit are more interesting, and of far greater value to mankind than these glittering gems from Golconda,[16] Brazil and the Dark Continent.[17]