In Paris they are to-day experimeüting with a new illuminant, which produces better results for less money than anything yet invented. It is the discovery of the French engineer, M. Denayrouze, who did as much to launch the electric light, twenty-five years ago. He has not only discovered a new lighting-factor but has invented a special lamp for its use.
"LUSOL,” as its maker explains, is merely a commercial name, for it cannot claim a chemical individuality. It is specially rich in carbon, and boasts the advantage over petroleum, motorcarline, etc., in having only a weak tension of vapor.
Without going into the processes of its extraction from coal, lusol may be briefly said to resemble acetylene, and can be called its twin—an acetylene, indeed, in liquid form and minus its explosions. Remembering that the great inconvenience of acetylene is the deposit of black smoke which it leaves, M. Denayrouze has preferred to renounce the incandescent carbon body, and to make use only of the calorific power by placing it in a lamp with an Auer mantle.
It was a matter of some consideration how best to use the ten thousand available calories. A special lamp was devised which deserves description. It is not only a lamp but a small distillery, very carefully made, and so closed as to prevent leakage. This is highly necessary, for
lusol being very fluid, very volatile, and highly inflammable, every precaution must be taken that not the slightest ooze takes place or the faintest breath of vapour escapes; nor must the most trifling effusion occur even should the lamp be overturned. For this reason it is furnished with a conical opening closed with a screw. When the burner is unscrewed, a central tube is found which reaches to the bottom of the receiver, and in this a tightly packed wick is fixed on a metallic axis. But a special characteristic is that the tube is closed at the top, so that the wick cannot emerge, and has thus no direct communication with the flame. The reason for this will be at once apparent when it is understood that all that is required of the wick is to. pump by capillary attraction the liquid lusol from below, and to trans-, port it to the little distilling compartment above. In a few words, it is not the lusol which burns, but the vapor.
By capillary attraction liquids rise in a higher or lower degree. Petrol-
eum will rise at seven degrees centigrade, alcohol at ten, and lusol at twenty-four. But in order to secure a vaporisation of any consequence heat is necessary, and to obtain this the inventor has utilized the flame of the lamp itself by means of a contrivance thought out for one of his previous notions. The support of the Auer mantle is usually of wire; but in this case the mantle-frame has been made solid, and soldered to the distilling chamber, being thus a good conductor of heat. When the lamp is working the mantle-frame becomes very hot, and communicates this heat to the liquid conveyed by the wick, which it distilled as vapor as long as the warmth continues. Simply expressed, the heat from the flame of the vapor causes more vapor to feed the flame.
The orifice which allows this vapor to rise is so minute that a fine needle can scarcely enter, and this As the only communication between the exterior of the lamp and the interior. It is, therefore, an impossibility that an effusion should take place. So nicely has the size of this orifice been regulated that it only allows just enough vapor to escape to ensure a sufficiency of air for rendering the flame not only illuminating but heating. It is, indeed, the well-known principle of the Bunsen burner. The little injector is also covered by a wire gauze enclosing a small space sufficient to complete the mixture of air and vapour, and to prevent the recoil of the flame and the danger of its reaching the spirit.
It was a little difficult to arrange for heating the top of the wick without burning it, a heat of one hundred and twenty-five degrees being required. This, however, must be continuous, for should a draught make this
flame flicker the lamp ceases its work of distillation. A small cupel in fusible metal gets over this difficulty by bringing into play the latent heat of the melting alloy.
The weak point in the lamp—and in this it is only similar to petroleum lamps with mantles—is its lighting. As long as the lamp burns, the circle, so to express it, of the flame creating the vapor to be transformed into flame works admirably; but when the lamp is extinguished its relighting causes a little delay, and seems an inconvenience to those accustomed to call up a gas-flame by merely striking a match, or to summon the electric light by simply turning a button. The lusol lamp can be lighted by alcohol in different ways; but aii ingenuous model has a second small burner which is easily lighted and which is self-extinguishing when the principal burner is in going order. Liquid alcohol has been replaced in this lamp by alcohol in tabloid form, and a recent improvement which prevents its evaporation allows the alcohol to be placed in the lamp when it is being cleaned in the morning, ready for lighting at night. The delay,slight though it may be, in lighting this lamp may perhaps deprive it of the favor of the impatient; but for the drawing-room or the study it is an ideal lamp, for it is quite silent, clean, does not leak, does not smoke, its wick does not require attention, it has no smell, and produces a steady flame of equable strength and having a brilliant white light.
As a test of its power, it should be stated that the incandescent electric lamps are usually made of ten, sixteen, and thirty-eight candlepower; the strongest petroleum lamp without incandescence is of fifty-
three, the corresponding Auer burner of fifty, and the acetylene of eleven candle-power The lusol model lamp as now presented is of one hundred candle-power.
It will, of course, be objected that lusol is highly dangerous; but what illuminant is not unless proper precautions are taken? Electricity electrocutes and short-currents cause fires, gas asphyxiates, and acetylene explodes. Petroleum’s dangers are too well-known to need mention. With care, lusol is not more dangerous. In its properly closed can it is absolutely innocuous, but must of course be kept away from the fire.
Inside the lamp it is equally safe, since it cannot escape in the form of vapor, while the flame has no free exit such as is the case with petroleum lamps, where it can recoil. The lusol lamp, it is claimed, can be turned upside-down without any danger. It does not heat, and after burning several hours remains normal. This is due to the ventilation of the central tube, which is double. This tube is made of an alloy that is a bad conductor of Icar, and it is one of the particular points of the invention. Should the tube become too warm the capillar y attraction is impeded. A thermometer plunged into the interior of a lamp which had been burning for several hours only registered one degree above that of the room.
The lamp is extinguished by closing the capillary orifice and this, unlike the extinction of the petroleum lamp, is prompt and radical. As long as the mantle-frame remains warm the lamp can be relighted without alcohol. Very great care is required in filling the lamp, which should be done away from fire or any light, and of course only when its light is
extinguished. The filling-cans are fitted with interior ventilation that prevents gurgling or splashing.
M. Denayrouze is more ambitious for his lusol lamp than to be satisfied merely to see it light interiors; he asserts that it is most valuable for outdoor illumination, especially where neither gas nor electricity is to be had. But it will be at once recognized that no mere wick could supply capillary attraction for & large flame, and it has been found necessary to help the lusol to rise in the wick by means of a pressure of air. Owing to the excellent way in which the lamp is closed very little air and a wTeak pressure secures the desired result, and the street-lamps are fitted with two small receptacles united by a rubber tube. One is filled with glycerine, and hangs about four feet and a half above the other, which is filled with air. The glycerine slowly runs into the lower can, and so sends the air into the upper, where it drives the lusol quicker through the wick. This arrangement need only be renewed once in twentyfour hours, when the glycerine is restored to its original position and everything starts again. There are other adaptations of this principle.
The advantage of the lusol lamp tvould appear to be its extreme illuminating power, and next its cheapness. In a domestic lamp fifty grammes of spirit are burnt in an hour, and it can be left burning a whole’ day at a cost slightly under threepence. In a three hundred and seventy-eight candle-power lamp, with the extra air-pressure, one hundred and ninety-two grammes only are consumed, with a pressure of a little over four feet of glycerine; while by increasing this four hundred and seventy-five candle-power c,an be
obtained. For outlying villages, isolated factories, or solitary houses the outdoor form of lamp seems particularly valuable while for interior use,
too, it seems to be exactly what is wanted. It will be interesting to watch the results of the Paris experiment.
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