Page:1902 Encyclopædia Britannica - Volume 25 - A-AUS.pdf/56

36 pungent odour disappears, and the pure gas has a not unpleasant etherial smell. It can be condensed into the liquid state by cold or by pressure, and Liquefac* experiments by Ansell show that if the gas be subjected to a pressure of 21'53 atmospheres at a temperature of 0° C., it is converted into the liquid state, the pressure needed increasing with the rise of temperature, and decreasing with the lowering of the temperature, until at - 82° C. it becomes liquid under ordinary atmospheric pressure. The critical point of the gas is 37° C., at which temperature a pressure of 68 atmospheres is required for liquefaction. A great future was expected from its use in the liquid state, since a cylinder fitted with the necessary reducing valves would supply the gas to light a house for a considerable period, the liquid occupying about Ao t^ie vo^ume the gas, but in the United States and on the Continent of Europe, where liquefied acetylene was made on the large scale, several fatal accidents occurred owing to its explosion under not easily explained conditions. As a result of these accidents Berthelot and Violle made a Explosi= series of valuable researches upon the explosion bilityof 0£ acetylene under various conditions. They

acetylides of the metals. The solubility of the gas in. various liquids, as given by different observers, is—

Volumes of Acetylene., 100 Volumes of absorb 5 Brine T 110 AV ater 600 Alcohol 150 Paraffin 100 Carbon disulphide 100 Fusel oil 400 Benzene 400 Chloroform 600 Acetic acid 3100 Acetone

It will be seen from this table that where it is desired to collect and keep acetylene over a liquid, brine, i.e., water saturated with salt, is the best for this purpose, but in practice it is found that, unless water is agitated with acetylene, or the gas bubbled through, the top layer soon gets saturated and the gas then dissolves but slowly. The great solubility of acetylene in acetone was pointed out by MM. Claude and Hess, who suggested charging SoIut]on acetone with the gas under pressure, a litre of acetone. acetone dissolving 360 times its own volume of the gas under a pressure of 12 atmospheres. When the acetylene, found that if liquid acetylene in a steel pressure is relieved the gas again escapes, and it was bottle be heated at one point by a platinum thought that in this way a better method of storing the wire raised to a red heat, the whole mass decomposes and gas would be provided by liquefaction. Experiment, gives rise to such tremendous pressures that no cylinder however, has shown that acetone thus saturated under would be able to withstand them. These pressures varied pressure shares many of the disadvantages of liquid from 71,000 to 100,000 lb per square inch. _ They, acetylene itself.

When acetylene was first introduced on a commercial moreover, tried the effect of shock upon the liquid, and found that the repeated dropping of the cylinder from a scale grave fears were entertained as to its safety, it being height of nearly 20 feet upon a large steel anvil gave no represented that it had the power of combining explosion, but that when the cylinder was crushed under with certain metals, more especially copper and Explosive OUr S a heavy blow the impact was followed, after a short silver, to form acetylides of a highly explosive ™™jj ' interval of time, by an explosion which was manifestly character, and that even with coal gas, which metals. due to the fracture of the cylinder and the ignition of contains less than 1 per cent., such copper the escaping gas, mixed with air, from sparks caused by compounds had been known to be formed in cases where the breaking of the metal. A similar explosion will the gas distributing mains were composed of copper, and frequently follow the breaking in the same way of a that accidents had happened from this cause. It was cylinder charged with hydrogen at a high pressure. therefore predicted that the introduction of acetylene on Continuing these experiments, they found that in acetylene a large scale would be followed by numerous accidents gas under ordinary pressures the decomposition brought unless copper and its alloys were rigidly excluded from about in one portion of the gas, either by heat or the contact with the gas. These fears have, however, fortufiring in it of a small detonator, did not spread far beyond nately proved to be unfounded, and ordinary gas fittings the point at which the decomposition started, while if the can be used with perfect safety with this gas. Acetylene was at one time supposed to be a highly acetylene was compressed to a pressure of more than 30 lb on the square inch, the decomposition travelled poisonous gas, the researches of Bistrow and poisonous throughout the mass and became in reality detonation. Liebreich having apparently shown that it p°0pert/es. These results showed clearly that liquefied acetylene was acts upon the blood in the same way as carbon far too dangerous for general introduction for domestic monoxide to form a stable compound. Very extensive purposes, since, although the occasions would be rare in experiments, however, made by Drs Grehant, Brociner, which the requisite temperature to bring about detonation Malooz, Crismer, and others, all conclusively show that would be reached, still, if this point were attained, the acetylene is much less toxic than carbon monoxide and results would be of a most disastrous character. The fact indeed than coal gas.

Acetylene has the property of inflaming spontaneously that several accidents had already happened accentuated the risk, and in Great Britain the storage and use of when brought in contact with chlorine. If a Chem!cal few piece's of carbide be dropped into saturated liquefied acetylene are prohibited. When liquefied acetylene is allowed to escape from the chlorine water the bubbles of gas take fire as cylinder in which it was contained into ordinary they reach the surface, and if a jet of acetylene be passed SoIld atmospheric pressure, some of the liquid up into a bottle of chlorine it takes fire and burns with a assumes the gaseous condition with such heavy red flame, depositing its carbon in the form of soot. rapidity as to cool the remainder below the tempera- If chlorine be bubbled up into a jar of acetylene standing ture of — 90° C., and convert it into a solid snow-like over water, a violent explosion, attended with a flash of intense light and the deposition of carbon, at once takes mass.

Acetylene is readily soluble in water, which at normal place. When the gas is kept in a small glass holder temperature and pressure takes up a little more exposed to direct sunlight, the surface of the glass soon, Solubility £pail own volume of the gas, and yields a becomes dimmed, and Bone has shown that when exposed acetylene, solution giving a purple-red precipitate with am- for some time to the sun’s rays it undergoes certain moniacal cuprous chloride and a white precipi- polymerization changes which lead to the deposition of a tate with silver nitrate, these precipitates consisting of film of heavy hydrocarbons on the surface of the tube..