Illuminating Gas

ILLUMINATING GAS, general name for flammable gases used for illumination; illuminating gas is also used for heating and for various laboratory and factory purposes. The most widely used is coal gas, obtained by dry distillation of coal (see Gas production), and carbureted water gas (see Illumination). Other types of illuminating gas (oil, peat, wood, methane, acetylene, etc.) have limited application. The constituent parts of illuminating gas can be divided into 3 main groups: 1) carbon-rich compounds that give brightness to the flame (ethylene, propylene, butylene, acetylene, vapors of benzene, toluene, xylene, etc.), 2) non-luminous compounds that determine the high temperature of the gas flame (H, CH₄, CO), 3) impurities (CO₂, N, water vapor, H₂S, carbon disulfide, NH₃, hydrocyanic acid, ammonium cyanide, etc.). The percentage ratio of the most important constituent parts of coal gas and water gas-see Gas production. Wood gas differs from coal gas and water gas by its higher content of heavy hydrocarbons (7-10%) and the presence of a large amount of CO (22-40%); it does not contain sulfur, cyanide, and ammonium compounds. Peat gas is close to wood gas in content of heavy hydrocarbons and CO. Oil gas is very rich in CH₄ (up to 60%) and heavy hydrocarbons (17-27%); it contains relatively little H (8-10%), the amount of CO is small, and it does not contain sulfur and ammonium compounds. When burned, oil gas produces soot and therefore requires dilution with lighter illuminating gas or the use of special burners. Methane (swamp) gas contains about 60% CH₄ and 30% H; it does not contain carbon monoxide. Recently, as a cheap source of its production, methane fermentation of sediments in installations for biological purification of fecal waters has begun to be used. Acetylene illuminating gas, obtained from pure calcium carbide, consists almost exclusively of pure acetylene C₂H₂; it must be well purified from extremely poisonous phosphine, which is present in it as an impurity. Along with electricity, illuminating gas is widely used for illuminating streets, squares, as well as stations, riding schools, and other buildings with large volume and good ventilation. Gas lighting is also often installed in residential apartments, but it is necessary to take into account the poisonous nature of illuminating gas and the possibility of accidents when it leaks from gas pipes. As a heating material, illuminating gas is used in gas stoves of various designs (see Heating). It has proved especially convenient for heating kitchen stoves and for heating water in special columns for baths. Such gas stoves and columns should be installed in multi-story buildings where the delivery of fuel to high floors is difficult; the products of illuminating gas combustion should be vented into chimneys. The Moscow gas plant in 1930 supplied 56% of the total amount of illuminating gas it produced for domestic needs, 35% for industrial purposes, and 9% for street lighting. The widespread development of gasification during the second five-year plan (1933-37) of socialist construction in the USSR should play a significant role in improving the living conditions of workers. In Moscow, Leningrad, Kharkov, Odessa, and Baku, a significant expansion of the gas industry is planned. In Baku, Grozny, Yeysk, and Stavropol, the development of gasification will be based on the use of natural combustible gas coming from the bowels of the earth in oil-bearing regions. In a number of cities having metallurgical industry (Dnepropetrovsk, Stalino), it is planned to use part of the factory gas for urban utilities. Of the sanitary hazards associated with the use of illuminating gas as an illuminating and heating material, one can point to a) the possibility of explosion, b) the danger of poisoning from inhaling air with an admixture of illuminating gas and c) the spoilage of air by products of illuminating gas combustion. Illuminating gas itself does not explode, but acquires this property when (due to leakage from a poorly closed tap or a rusted pipe) it mixes with room air in an amount of 7-25%. If you enter such a room with a burning candle or strike a match, a dangerous explosion occurs. The strongest explosions are given by mixtures with a content of 12-20% illuminating gas. At 26% and more, no explosion occurs. Acetylene, used as illuminating gas, explodes already with an admixture of 3.3% to air and retains its explosive properties up to the limit of 52%. Methane (swamp) illuminating gas is no less dangerous in terms of explosibility. The danger of poisoning from illuminating gas is due to its high CO content (see Carbon monoxide). According to Lehmann, illuminating gas containing more than 7% CO should be considered poor from a sanitary point of view, however in practice illuminating gas often contains up to 10% CO. Water gas poses the greatest danger in terms of poisoning, in which the CO content reaches up to 30%. Due to its cheapness, water gas has wide distribution, especially in America, where it is used both for lighting and as a fuel for gas engines and for supplying laboratories. Many cases of poisoning by this gas have been described. Due to the high toxicity of illuminating gas in rooms with gas lighting, constant and very careful supervision of the condition of gas pipes and taps is required. The unpleasant sharp smell of coal gas (depending on the content of sulfur-containing organic substances, naphthalene, etc.) makes it possible to fairly easily detect by smell an admixture of 0.01-0.02% illuminating gas to room air and in time to take appropriate measures to prevent dangerous poisoning. If the smell of illuminating gas is very weak or if it is mixed with air that already contains many odorous substances, one cannot rely on the sense of smell and should analyze the air for CO content. It is very important to find and eliminate the cause of the gas leak. As a rule, gas pipes in apartments should be laid so that they are easily accessible for inspection in case of gas leakage. To locate the leak, a burning candle flame is passed along the gas pipe, and the illuminating gas escaping from cracks in the pipe ignites. In rooms where there is a sharp smell of illuminating gas, this kind of experiment should be performed only after good ventilation of the room to avoid explosion. The tightness of gas taps is checked in the same way, and also the grooves of the taps are lubricated with a strong soap solution, and the seeping gas gradually forms soap bubbles. When street gas pipes are damaged, the soil very actively absorbs the odorous substances of illuminating gas and it can completely lose its characteristic smell, however it retains the toxic properties inherent in CO. If the soil is asphalted or covered with an icy crust and snow, illuminating gas from a damaged street pipe can spread for tens of meters from the point of damage, penetrate into basements and lower floors of nearby buildings and cause severe suffering. Such poisonings can occur unexpectedly, since the deodorized by soil illuminating gas cannot be detected in time by smell. The most dangerous time is winter, when houses are heated and the heated air of the basement floor tends to rise up, sucking in air from the soil. As for the spoilage of air by products of illuminating gas combustion, in addition to the formation of a large amount of CO₂ and water vapor, as well as significant heating of the air in the room, coal gas, poorly purified from sulfur and ammonium compounds, when burned forms a large amount of sulfuric acid, as well as sulfurous and nitric acids, the latter under the influence of water turning into nitrous and nitric acids. In damp apartments with gas lighting, water vapor, settling on cold objects, gives condensation water of strongly acidic reaction, which has a destructive effect on the strength and color of fabrics of soft furniture, curtains, etc. In sanitary analysis of illuminating gas, main attention is paid to the percentage content of CO in it, as well as the admixture of ammonia, hydrocyanic acid, hydrogen sulfide, carbon disulfide, and sulfur-containing organic compounds. Illuminating gas should be free of ammonia, and wet curcuma paper should not turn brown under its influence. There should be absolutely no hydrogen sulfide in illuminating gas, and filter paper impregnated with an alkaline solution of lead acetate should not blacken from the action of illuminating gas on it. The admixture of CO₂ to illuminating gas does not have a harmful effect on health, but reduces the illuminating power of illuminating gas. The presence of a significant amount of O₂ in illuminating gas indicates the permeability of gas pipes to air. Good illuminating gas with an hourly consumption of 150 l should give in an Argand burner a light intensity of at least 17 lux. The heat productivity of 1 m³ of illuminating gas is on average 4,000-4,500 calories.

N. Ignatov. Discovery in forensic cases. Discovery of illuminating gas amounts to the discovery of carbon monoxide (see Carbon monoxide, discovery) and cyanide compounds (in case of insufficient purification) when the latter are absorbed by a solution of caustic soda (see Hydrocyanic acid, discovery in forensic cases).