COAL GAS, GASOLINE GAS, AND ACETYLENE Gas.—Gas for illuminating purposes was invented by William Murdoch in 1792 at Redrutch, Cornwall, England. It was first used in the United States in 1806 by David Melville, of Newport, R. I. It was introduced in Boston in 1822, and in New York the year following. Gas is now used for heat ing and cooking as well as for illu minating purposes by upward of half the population of the United States. As its convenience and economy be come better known, the number of towns and villages to introduce gas will no doubt steadily increase.
Coal gas is made by distilling bitu minous coal with heat in a retort, con densing and separating it from the water, vapor of tar, and other solid substances, and purifying the result `Jig product to remove the compounds of sulphur and carbonic-acid gas. A by-product of this process is coke, about one third of which is required for heating the retorts; the rest is sold. Other by-products are ammonia water and coal tar.
Illuminating gas consists of nearly equal parts of hydrogen (which burns with a blue flame, giving heat but no light), marsh gas, and other hydro carbons (which burn with a luminous flame, but deposit soot if not fully consumed), and small quantities of carbonic oxide, and nitrogen, which are impurities and diminish the illu minating power of the gas.
Gas, after being purified, is usually stored in a cylindrical tank with a conical top made of iron plates float ing in a cistern of water. This is so arranged to exert a uniform pres sure on the gas equal to that of a column of water 6 inches high. The pressure serves to distribute the gas in the mains. These are usually made of cast iron from 24 inches down to 3 inches in diameter and laid about 3 feet under ground. The mains are connected with the buildings of con sumers by service pipes, which should be below the frost line. Otherwise they may be closed by hoarfrost caused by the freezing of the watery vapor contained in the gas. The gas is measured by means of a house meter before being distributed to all parts of the building.
Gas Meters.—The gas meter is not constructed like a clock, as the dial seems to suggest; hence, contrary to common belief, a gas meter in good order cannot run either too fast or too slow. The meter is an engine in
which the gas is the motive power. Unless the gas actually passes through the meter, the latter does not move. The dials mechanically and actually record the number of revolutions in cubic feet. The popular notions that gas meters are often inaccurate, and that an increased pressure or the practice of turning on the gas with full force when first lighted may make the meter spin faster and record against the consumer, are erroneous. Of course the meter records all gas which passes, including that which is wasted as well as that which is used. Hence gas jets should be regulated so as to prevent " blowing " or the pass ing of unconsumed gas. This regula tion neutralizes the effect of any in crease in the pressure in the gas mains. Contrary to common belief, most in juries to a meter work against the company. Any apertures caused by use in the interior of the meter may allow the gas to get through without being recorded. Not infrequently the valves of a meter become fixed so as to let gas through without being reg istered. Hence meters are tested at intervals by inspectors, who pass a certain number of cubic feet through them and note whether or not the dials make proper record.
Amount of Gas Consumed.—Learn to read the gas meter and thus note what amount of gas is being con sumed. The ordinary flat-flame burner should consume 5 or 6 feet of gas an hour. If badly adjusted or of faulty construction, it may consume 10 to 15 cubic feet an hour. A Welsbach burner uses only about 3 feet an hour. A medium-sized two-oven range with all burners lighted consumes about 60 feet an hour. A gas cylinder stove about 24 feet an hour. At least once a month make a test by reading the gas meter in the morning, noting care fully the time each burner is lighted, and again reading the gas meter at night. If the quantity consumed is greatly in excess of the above figures it indicates that the burners are poor ly adjusted. In that case notify the gas company, whose duty it is to regu late the burners, and to keep them in order. Gas is the most economical of fuels if used with intelligence and care.