In Within the last twenty years the use of gas production. In New York city and Brookhas increased with great rapidity throughout lyn, it has ranged from $2.00 to $4.50, the cities and towns of the United States. standing at present at $3.25, but with a In 1860, the number of companies manufac- promise of reduction soon to $2.75. turing gas was, according to the statements of the American Gas Light Journal. 433, representing a capital of about $59.000,000. In 1870, the number of companies had increased to somewhat more than 800, and the capital represented to over 112,000,000, thus ranking with the most important branches of industry in the country. The capital of the gas companies of the State of New York, is stated by Mr. Wells in his Report on Local Taxation, to have been $20,000,000 in 1870, and in this estimate many of the smaller companies are overlooked. The capital of the gas companies of New York and Brooklyn in 1871 was over $14,000,000. There are certainly five and probably six companies whose annual production exceeds 1,000,000,000 cubic feet, and several others are approximating to that amount. The price per thousand feet has varied greatly in different sections, and has fluctuated in all cases with the price of the coal and in its Char Philadelphia, where the city manufactures for its citizens, it is now, we believe, $2 25, and in Pittsburg has been as low as $1.50. In the smaller cities it ranges from $4.00 to $8 00 per thousand feet. On the Pacific coast, owing to the high price of gas producing coals, it has been as high as from $8.00 to $14.00 per thousand feet. If the Rocky Mountain coals prove to be of good quality for the production of gas, the cost will be materially lessened. Notwithstanding the consumption of petroleum oils, there has been an increase in the demand for illuminating gas, and the plans proposed for its production from other hydrocarbons, or by new processes, have generally failed, so that there seems to be a probability of the continued production of gas from coals What new methods of illumination the next twenty years may develop we cannot say; but it is certain that a cheap, safe, and brilliant illuminator is still a thing to be desired. SOME OF THE PRINCIPAL GAS LIGHT COMPANIES IN THE UNITED STATES. tered. Chartered 1830, Manhattan, N. Y.. .$4,000,000 1823, New York, N. Y.. 1,000,000 430,000,000 1825, Brooklyn, N. Y.. 2,000,000 163,000,000 2.00 1859, Citizens' Co., Brooklyn. 1841, 1822, Boston, Mass... 1851, Cincinnati, Ohio. 1849, Chicago, Ill.. 1846, Charleston, S. C.. 74,500,000 1848, Providence, R. I.. 1848, Troy, N. Y.... 1851, Richmond, Va. 1852, Rochester, N. Y.. 1849, Lowell, Mass.. TOTAL OF GAS COMPANIES IN THE UNITED STATES FROM RETURNS OF JULY, 1860. The preparation of illuminating gas from and the rapidity with which the operation is bituminous coal, wood, rosin, and other conducted. The object in this special disbodies of organic nature, is a chemical proc-tillation is to obtain the largest proportion ess, too complicated to be very fully treated of the gases richest in carbon, particularly in this place. When such bodies are intro- that known as olefiant gas, which consists duced into a retort and subjected to strong of 86 parts by weight of carbon and 14 of heat, the elements of which they consist, as hydrogen, represented by the formula C carbon, hydrogen, oxygen, and nitrogen, re- H. This and some other gaseous hydrosolve themselves into a great variety of com- carbons of similar composition, or even conpounds, and escape (with the exception of taining a much larger amount of carbon in a fixed carbonaceous residue of charcoal or the same volume, and hence having a corof coke) through the neck of the retort in respondingly greater illuminating capacity, the form of gas or vapors, some of the it is found, are produced most freely from latter of which condense on cooling into carbonaceous substances which contain a liquids and solids. These compounds are large proportion of hydrogen compared with rendered more complicated by appropriating that of oxygen. Many of the common bithe elements of air and moisture that may tuminous coals contain about 5.5 per cent. be present in the retort or in the crude ma- each of hydrogen and oxygen, the rest beterial, and also of the foreign substances or ing carbon. Boghead cannel of Scotland impurities contained in the latter. In proc- contains 11 per cent. of hydrogen and 6.7 esses of this kind, the products vary great- of oxygen; rosin 10 per cent. hydrogen and ly in their character and relative proportions 10-6 oxygen; wood 5.5 hydrogen and 44.5 according to the degree of heat employed, oxygen." Of such compounds the cannel yields the richest gas and in largest quanIf too much carbon be present a part of tity. Still, as will be more fully explained it escapes unconsumed and produces a hereafter, the process may be so conducted smoky flame, hence the necessity of the dias to obtain chiefly liquid instead of gaseous luents or gases deficient in carbon for neuproducts. With the olefiant gas and the tralizing the too large proportion of those others of similar composition, a number of gases richest in carbon. The noxious comother gases also appear, some of which seem pounds in illuminating gas, and which to be essential for producing the effect re- should be as far as possible extracted from quired in illuminating gas, though they do it before it is delivered for consumption, are not themselves afford light by their combus- the sulphurous ingredients formed by the tion. Their part is rather like that of nitro- combination of the sulphur of the iron gen in the atmosphere, to moderate the in- pyrites commonly present in bituminous tensity of the more active agent of the mix- coals with the carbon, and with the hydroture. Such are the light carburetted hydro- gen and the ammoniacal products. They gen, carbonic oxide, and hydrogen, all of are the highly offensive sulphurets of carbon, which are inflammable, but possess little or the sulphuretted hydrogen, etc. Carbonic no illuminating power. The first named acid, nitrogen, oxygen, carbonate of ammocontains in an equal volume only half as nia and aqueous vapors are to be regarded much carbon as olefiant gas, its composition as foreign substances, though always present being represented by the formula C, H, to some extent in the gas. and if its proportion is too great for the purpose it serves as a diluent, the quality of the gas is impaired, and must be corrected by the use of richer material or increased care in the process. The light produced by the combustion of gas is variable, not only according to the quality of the gas, but also according to the manner in which it is burned. If its elements undergo the chemical changes which constitute combustion simultaneously, the hydrogen combining with the oxygen of the air to form aqueous vapor, and the carbon with oxygen to produce carbonic acid, no yellow flame appears, but instead of this, a pale blue flame like that of hydrogen alone. Such an effect is produced when air is thoroughly intermixed with the gas as it passes through a tube to the jet where it is ignited. But if the conditions of the combustion are such that the hydrogen burns first and appropriates the oxygen in contact with the gas, the particles of carbon are brought to an incandescent state and produce the yellow light before they reach the oxygen with which they combine. The particles may even be arrested while in transitu and be deposited upon a cold surface in the form of soot. The greatest heat is produced with the most thorough mode of combustion and the appearance of the pale blue flame; and lamps designed to give great heat are now in general use among chemists, in which gas is burned in this manner. When the air is impelled by a bellows they even produce an intensity of heat sufficient for many crucible operations. The liquids generated by the distillation mostly condense in two layers on cooling, the upper an aqueous fluid, rendered strongly alkaline by the ammoniacal compounds in solution; and the lower a black tarry mixture commonly known as coal tar, which is composed of more than a dozen different oily hydrocarbons, as benzole, tuluole, etc., and contain in solution the solid oily compounds of carbon and hydrogen, as naphthaline, para-naphthaline, and several others. Many of these are likely to prove of considerable practical importance. Benzole is a highly volatile fluid, a powerful solvent of the resins, india-rubber, gutta percha, greasy matters, etc. A most beautiful light is produced by the flame of benzole mixed with due proportions of common air, and the mixture is effected by passing a current of air through the fluid, the vapor of which it. takes up and carries along with it. The difficulty attending this application is the condensation of the benzole and its separation from the air at temperatures below 50°. Above 70° too much vapor is taken up, and the effect is a smoky flame. In Europe much attention has been directed to the separation of the more hidden products of coal tar; and among these the following are enumerated in a statement exemplifying the rapid increase in the value of these products as they are obtained by more extended researches. Benzole worth about 25 cents a pound; nitro-benzole, a substance having the odor and taste of bitter almonds and used as a flavoring, worth, crude, 70 cents, or refined, $1.50 per pound. The or dinary aniline dye for producing the mauve color, $4.50 to $8 per pound, and the pure aniline violet in powder $240 to $325 per pound, or about its weight in gold. whole length of the furnace stacks. This is called the hydraulic main, and into it all the volatile products from the retorts beneath are discharged. It is kept about half Gas works established in cities and towns filled with water or the liquid tarry matters, are commonly built in places where the and the dip pipes terminate about three property and buildings around are least like- inches below this fluid surface. By this ar ly to be injured by the escape of the prod-rangement the retorts are kept entirely indeucts, and rather upon a low than a high pendent of each other, while their products level, for the reason that the gas on account all meet in one receptacle. of its lightness compared with the atmospheric air ascends more freely than it descends to its points of communication with the external air. The works consist of the apparatus for distilling the coal and receiving the products of the distillation, that for purifying the gas, and that for conveying it to the places where it is consumed, and there measuring the quantities supplied to each customer. The retorts in general use are either of cast iron or of fire clay. The latter are a late improvement highly recommended, and introduced at the present time into a few of the gas works. Various forms have been tried; the most approved are of shape, 7 to 9 feet long, 1 or 2 feet wide, and 12 or 15 inches high. They are set in the furnace stacks, commonly two on the same horizontal plane, two more over these, and a fifth at the top. A single furnace fire below is sufficient for heating them, and the capacity of the works is increased by multiplying these fires along the length of the stacks. Sometimes the stacks are made double, so as to take two retorts set end to end, each opening on opposite sides of the stack. In place of two retorts a single long one has been substituted, passing entirely through and having at each end an opening for charging and discharging. In large establishments as many as 600 or more retorts may be set, all of which may be kept employed in the winter season, when the consumption of gas is largest. The outer end of each retort projects a little way in front of the wall of the furnace, and is provided with a movable mouth-piece covering the entire end, which may be readily removed for admitting the charge of coal. Upon the top of this projecting end or neck stands the cast-iron pipe of about 4 inches in diameter, called the stand pipe, through which the volatile products pass from the retort. It rises a few feet, then curves over back, and passes down into a long horizontal pipe of large diameter, which is laid upon the outer edge of the brick-work, and extends the In manufacturing gas it is found necessary to introduce the charge into the retorts already at a full red heat, and bring it as rapidly as possible to the high temperature required for producing the richest gaseous hydrocarbons. A low and slowly increas ing heat causes the ingredients of the charge to form a large proportion of liquid and oily substances, and little gas. It is only while the coal is approaching a vivid red heat that the best gaseous mixtures are obtained; and even these are deteriorated by change in the composition of the olefiant and other rich gases of which they are in part composed, if the mixture is exposed to too high temperature, or remains in contact with red hot surfaces of iron. The duration of the charge used formerly to be from 8 to 10 hours; but from the observations of the qualities of the gases evolved at different stages of the process, it has gradually been reduced to 4 to 6 hours, varying according to the character of the coal employed. The richest gases are obtained in the first hour, and after this the proportional quantity per hour steadily diminishes at the same time that the quality gradually deteriorates. The temptation, however, to obtain the largest amount of a commodity which is sold only by measure, and to consumers who have no means of assuring themselves of its real quality, no doubt often leads to extending the operation to the separation of gaseous mixtures having very little illuminating power. The manufacturers knowing their materials, and checking their operations by regular photometrical tests, can control the quality of the product as they see fit. In order that the least loss may be incurred in bringing the charge up to the proper temperature, the retorts are kept at a full red heat; and when ready for a new charge the mouth-piece is partially removed, and the gas that escapes is ignited. When the danger of explosion by sudden admission of air has passed the lid is removed, and the red hot coke is raked out and quenched with water. The new charge is then introduced by means of a long iron scoop bent up at the sides, which is pushed into the retort, and being turned over, discharges its contents. The mouth-piece is then replaced, and tightly secured with a luting of clay or lime. It is obvious that the more perfectly the coal is freed from moisture, the better must be the gas; and if it were also first somewhat heated, the result would be still more satisfactory. The coals employed at the different gas works of the United States are generally mixtures of the caking coals of the interior, or of those of Richmond, Virginia, and of Nova Scotia, with cannel coal, which for the cities near the coast is imported from Great Britain, and for those in the interior is obtained from the mines of this coal in western Virginia and in Kentucky. The larger the proportion of cannel, the better should be the gas, under the same method of manufacture. In the works in New York city, the proportion of cannel is generally from one third to one fourth of the whole. Other establishments generally use a less proportion of it. The amount of gas it may produce varies with the kind of cannel from 9500 cubic feet to the ton to 15,000 cubic feet. The last is the yield of the Boghead cannel. In general, the greater the yield the better also is the quality of the gas, as is indicated by its increased specific gravity, that of the cannel last named being .752, while the gas from other cannels yielding about 10,000 cubic feet may not exceed .500. The best Newcastle coals are not inferior, either in the amount or quality of the gas they afford, to most of the cannels. They produce about 12,000 cubic feet of gas to the ton, and of specific gravity sometimes exceeding .550 or even .600. The specific gravity is not depended upon as a certain test of the quality of the gas, the density of which may be increased by presence of impure heavy gases, or even of atmospheric air; but it is resorted to only as an indication in the absence of more exact tests. The coke obtained from the retorts, amounting to about 40 bushels to the ton of coals, furnishes all the fuel required for the fires beneath, and three times as much more, which is sold for fuel. As the volatile products pass through the hydraulic main, the principal portions of the oily and ammoniacal compounds are deposited in it; but some of these pass on in vapors, and would, if not separated, cause obstructions in the pipes in which they might condense in liquids and solids. They are consequently passed through a succession of tall iron pipes standing in the open air, and sometimes kept cool by water trickling down their outside. A pipe from the bottom of each pair conveys the condensed tar and ammonia into a cistern in the ground. To still further separate the condensable portions, the gas at some works is next passed into the bottom of a tower filled with bricks, stones, etc., among the interstices of which it finds its way up, at the same time that water constantly sprinkled on the top is working down and keeping the whole cool. The water washes away the remaining ammonia; but it is to be feared that it also removes some of the richest hydrocarbons, and the use of the wet scrubber, as it is called, is already abandoned at some of the gas works for similar methods of condensing, except that the water is dispensed with. The gas makes its exit from the top of the scrubber; and its passage being already somewhat impeded so as to throw considerable pressure back into the retorts, thus effecting chemical changes in the gas, which impair its quality, it is found necessary to introduce a revolving exhauster, which takes off this pressure, and at the same time propels the gas forward into the succeeding apparatus. This is first a purifier, the object of which is to arrest the carbonic acid and sulphurous gases. Dry quicklime, and also the solution of this in water, known as milk of lime, have the property of absorbing these gases as they are made to pass among the particles of the one spread upon shelves, or interspersed among a porous substance such as dry moss; or to bubble up through the aqueous solution. The lime as it becomes saturated with the impure gases is replaced with fresh portions. The cleansing process is now complete, and the gas is in proper condition to be delivered to the consumer. It must first, however, be measured, that a record may be kept of the quantity produced, and it is next conducted into the great gas-holders in which it is stored. The measurement is effected by means of a large station meter, constructed on the principle of the small servicemeters, with one of which each consumer is supplied. A revolving drum with four compartments of equal capacity is made to rotate in a tight box by the gas entering and filling one of these compartments after another. |