Beautiful Motor Vehicle Rebate Certificate e from the American Liquid Air Company issued in 1899. This historic document has an ornate border around it. This item has been hand signed by the Company’s President, Stephen B. Emmens and Secretary, and is over 116 years old.
The American Liquid Air Company which was headquartered in New York City at the turn of the century.
Reported in The American Magazine, Volume 48 - 1899
IF a gas is allowed to expand against resistance, work is done ; the mechanical energy so expended is simply a transformation of heat—the disappearance of which produces cold. In an air pump we see the air under the receiver become so chilled that moisture is deposited in drops on the glass. Miners and engineers, who use compressed air in operating tools, find it necessary to apply heat where the air escapes, to prevent the valves from freezing. This familiar cooling by expansion is the principle of the process used in liquefying air.
Heat, according to the generally accepted theory, is a mode of vibration of the molecules of matter. Light, electricity and magnetism are also supposed to originate in the motions of the ultimate particles of matter. These motions arc frequently associated with each other, and it is well known that heat and electricity may be caused by, and changed into, mechanical forces —as through the agency of an engine or dynamo. The fact that energy, like matter, may be completely transformed but cannot be destroyed, is expressed in the doctrine of the conservation of energy. When some new manifestation of energy becomes known some people are always ready to believe that the energy itself is new. But all the evidence we have goes to show that neither energy nor matter has ever been created by human power, or by any other power since the creation of man.
To run an engine to operate an electric plant or a liquid air plant as a source of energy, is like pumping water to the top of a building and using it there to operate hydraulic elevators. Such plants are often very useful, not because they produce power, but because they transform the stored energy of coal into other forms of energy which are more easily distributed and applied. Liquid air may remain for several years, as electric lights did, a laboratory and lecture room curiosity. But there is abundant reason for believing that such low temperature, produced at low cost, will have many useful applications, and that liquid air and liquefying apparatus will have considerable commercial importance. A great deal of nonsense has been written along this line, and published broadeast in Sunday newspapers and popular magazines. 1t is quite certain that the liquid will not be used in some of the ways claimed. It will not be used to make more liquid of the same kind; it will not be used generally as a substitute for ice, and under ordinary circumstances it will not be used expansively in place of steam. The first claim, which is an absurdity, was probably the result of experimenting with a plant which had been already cooled to liquid air temperature by steam power, so that a very little liquid air, or any other source of power, would serve to operate it for a few minutes.
As a refrigerating agent liquid air will produce temperatures so low that ice is hot in comparison. But for temperatures around the freezing point nothing can generally compete with ice; although when a rapid and continuous current of cold air is wanted the vaporization of liquid air will furnish exactly what is needed without any machinery.
As an expansive agent in motors it has been shown by Mr. Hudson Maxim that liquid air has a value of about seven-twelfths that of steam, and evidently cannot compete with it in that way where economy is the chief consideration.
The commercial value of liquid air will depend largely upon the practicability of its economical transportation and preservation. This makes a subject by itself. The present methods, which are very satisfactory in the laboratory, may be improved where large quantities of the liquid are to be handled and stored. When we consider that the difference in temperature between the liquid and ordinary air is more than twice the difference between freezing and boiling water, and that the liquid immediately evaporates when raised above its limiting temperature of _312° Fahrenheit, it seems strange that a pint of the exposed liquid will not disappear in less than half an hour. One reason is that small quantities are self-protected by assuming the spheroidal state. When any liquid is put on a surface very much hotter than itself it instantly evaporates enough to form a cushion of vapor which prevents actual contact between the liquid and the solid, and so prevents conduction of heat. The superficial tension of the liquid draws' it into a globular form Which is supported on the vapor, the particles of which constantly vibrate between the solid and the liquid. Water on red-hot iron is the most familiar example of this state; drops of it will roll like mercury. Handling liquid gas is like handling water in red - hot vessels; it is protected to some extent by its own vapor.
Liquid air may be stirred by the bare fingers without injury, just as a finger may be passed quickly into melted metal provided the hand is moist. When the hand is put in melted lead the high temperature of tlie lead vaporizes the water, which forms a non - conducting layer protecting the hand hetter than any glove of solid matter. In the other case the phenomenon is reversed. The hand is now the hot substance, whose temperature differs from that of liquid air more than it does from that of melted lead.
To preserve the liquid air it is necessary to put it in a receptacle where heat vibrations cannot be imparted to it. The same means which will prevent the carbon filament of an incandescent electric light from dissipating its heat will prevent objects at ordinary temperature from imparting their heat to liquid air. Professor Dewar has been very successful in this work. His glass bulbs are made double, and the space between them being exhausted of air both conduction and convection are prevented. A drop of mercury put between the bulbs will vaporize in the vacuum, and then when the inner bulb is filled with liquid air the vapor is deposited on its surface and thus makes a mirror. This mirror reflects the radiant heat and light which otherwise would get in. In this way the influx of heat is reduced to one-thirtieth of what it would be with an air space. When such a bulb is put inside of another Dewar bulb, or is immersed in liquid air, its contents are kept without appreciable loss. Professor Dewar has thus fully solved the problem of keeping small quantities of liquid air in the laboratory.
Mr. Tripler, who has the distinction of being the first man to make and distribute liquid air by the gallon, keeps the liquid in tins or cans wrapped in boiler felt or steam pipe covering. The tops of the cans are covered only with pieces of the same material, so that the gases can easily escape. To pack for transportation one can is simply thrust into a larger can. A three-gallon milk can of the liquid, thus protected, loses about one gallon in a nine hours' ride.
Probably there will be no serious difficulty in using large Dewar jars, or in confining the liquid under pressure with a safety-valve and using the escaping gases to refrigerate the exterior of the can. Tank cars could be constructed on cither of these principles, so that the liquid might be transported for thousands of miles and kept for many days. The larger the tank the less the percentage of loss would be, because the surface varies as the square, while the volume varies as the cube of the linear dimensions. This law is very evident in the case of ice—which is always broken in small pieces to secure a rapid melting or cooling effect.
Professor Elihu Thomson has suggested the possibility of having well-protected liquid-air pipe lines laid from sources of great natural power—for example, Niagara Falls—to large cities where the liquid could be tapped as required. The pressure in the pipe could be regulated by safety valves, and would be moderated by tapping en route. The air might be drawn out either in liqnid or gaseous form—according as it was tapped from the bottom or top of the pipe; it might be used directly for refrigerating houses in summer, and by superheating it would operate electric dynamos and other machinery. Ice could be made as a by-product.
One of the advantages of a liquid-air pipe line is seen in the fact that pure copper and other electric conductors offer a resistance to the electric current which is proportional to their temperature. Consequently a thin copper wire laid in or along such a pipe could carry a heavy current with little loss. The electricity, of course, could be generated by dynamos at the water-power where the air would be liquefied. Moreover, all insulating materials have their insulating quality enhanced at low temperatures, so that the liquidair pipe line would have great attractions for the electrical engineer, and the great evil of electrolysis, or leaking electricity, in our city streets might be avoided. Owing to the present high price of copper, earnest efforts are being made to find substitutes for that metal. If the air pipe itself could be successfully used as an electrical conductor a great economy would be effected in long-distance transmission. Where water power is not available there are generally large power plants which are not operated more than twelve hours a day, and when not otherwise used they might operate air-liquefying machinery. The realization of such possibilities as these will greatly promote the cheap production and extensive use of liquid air.
Safety in handling and distribution is another important consideration. If a liquid-air reservoir is air-tight it will burst with violence, unless able to resist a pressure of more than five tons to the square inch, and this is several times the working pressure generally allowed for compressed air. As long as the escape of gas is allowed there is no danger in handling the liquid provided it is not brought into contact with any burning substance. What happens in the last case depends on circumstances, and experiments should be made with caution. Nitrogen, which constitutes four-fifths of the atmosphere, is perfectly inert. It is oxygen which does all the work, and it is so active that if it wore not mixed with the nitrogen the world would soon be consumed. Now liquid nitrogen is more volatile than liquid oxygen—boiling at _377° Fahrenheit, instead of _3560 Fahrenheit; consequently liquid air loses nitrogen faster than it does oxygen, and the proportion of the latter is constantly increasing. When the liquid has about half disappeared the remainder is generally about half oxygen; it is then capable of supporting rapid combustion or explosion when in contact with burning carbon. Dr. Linde has made liquefiers which separate the dangerous but useful oxygen from the nitrogen, and it is probable that this separation will be made in the commercial article. The nitrogen would be always harmless, and for purposes of expansion and refrigeration would be more useful than the mixture. The oxygen, on the other hand, has many applications of its own in various industries.
Among the possible uses of liquid air and its constituents we will name a few:
(1). A substitute for compressed air. With a pressure of only one thousand pounds to the square inch compressed air requires very strong steel reservoirs. But the liquid, containing eleven and one-half times as much air and potential energy, may be carried in a paper box. Of course the liquid is subject to constant waste by evaporation, while the compressed air does not waste, but for some purposes—where a light compact source of energy is required, which can be immediately regulated to varying loads—the liquid will have a great advantage.
(2). For gas engines. When the liquid is rich in oxygen it may be used with carbon as an explosive in interior combustion engines.
(3). In aerial navigation. One of the greatest obstacles to the construction of a practical dirigible balloon, aeroplane, or flying machine, has been the lack of an adequate power with little weight. The flight of the most sue
cessful of these machines has been very limited, because the amount of power which could be carried was so quickly expended. Liquid air seems likely to furnish exactly the power that is needed. It may cost twice as much as coal per horse-power hour, but it will do twice as much work as steam of equal weight, and it dispenses with the weight of fuel and boiler which has hitherto prevented any prolonged aerial navigation.
(4). In submarine navigation. Liquid air after furnishing power by expansion in a motor would provide a supply of pure air for breathing. When any form of combustion engine is used it is necessary to insure a constant supply of oxygen or compressed air both for the fire and for breathing.
(5). In deep-sea diving. Since the weight of the liquid is about that of water, it may be easily handled in casks under water. A pipe line from a forty-gallon cask to the diver would supply him with air enough for several hours. Power might be supplied in the same way, but probably freezing of the water around the safety valves and working parts would prevent any continuous operations.
(6). As a freezing mixture in pipes around tunnels and shafts. One of the best ways of excluding water from mines and tunnels during construction, where its influx would result in stoppage of work and perhaps loss of life, is to freeze the surrounding earth. This has been accomplished by using freezing mixtures, which are put in pipes properly spaced around the excavation. Liquid air would seem to be much better for this purpose than any freezing mixture, since its far lower temperature would freeze water a greater distance from each pipe and so reduce the number of pipes needed. Liquid air will also be very useful in some mines for cooling and ventilation.
(7). In making vacuum bulbs, sucb as are used in electrical and other apparatus. The most perfect vacuum known has recently been made in this way: A glass tube more than thirty inches long and terminating in two bulbs is filled with mercury. After filling the tube the mercury is boiled to expel any air that may be mixed with it; then the tube is inverted in a vessel of mercury. The pressure of the atmosphere, per unit of area, on the surface of the mercury is equal to the weight of a column of mercury thirty inches high; consequently the bulbs being more than thirty inches above the open surface are filled only with the vapor of mercury. In this position the two bulbs are hermetically sealed with the blow-pipe. Then by chilling the smaller bulb with liquid air, this vapor is condensed to a solid and deposited as a mirror on the interior of the bull). The tube connecting the two bulbs may now be sealed off with the blow-pipe and the larger one then contains the most perfect vacuum obtainable by any known process. In this way it is easy to reduce the vapor to two and one-half millionths of a millionth of an atmosphere. This means that if it were possible to make such a bulb a quarter of a mile in diameter there would not be enough vapor in it to produce atmospheric pressure in a bulb only one inch in diameter. Professor Dewar claims that this is a higher vacuum than any which had been previously dreamed of, and Professor t'rookes acknowledges its superiority to his own, which is made only by hours of work with the mercurial pump.
(8). In blasting work. One of Mr. Tripler's startling experiments shows that heavy felt, which can scarcely be induced to burn in open air, burns so rapidly as to explode when it is saturated with liquid air. In any explosive mixture liquid air is chiefly remarkable for its volatility—which would sometimes be an advantage, but often a disadvantage. Practical experiments in a (Serman coal mine showed that such a mixture maintains its full force for only five or ten minutes, and within half an hour, or as soon as tbe liquid has evaporated, all explosive power is lost. In regard to the amount of this power Mr. Hudson Maxim, the smokeless-gunpowder inventor and a high authority on explosives, writes as follows in a communication to the writer of this article: "An explosive compound is one which contains oxygep for the support of its own combustion; that is to say, it consists of combustible matter intimately associated with oxygen. Explosive compounds are burned in two ways; one by surface combustion, the other by what is called detonation, and which is practically instantaneous. Gunpowder is a form of explosive which is consumed by surface combustion and this, although rapid, is very slow compared with the action of detonation. Detonation compounds are termed high explosives and are too quick for use as gunpowder.
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