The item of "olefiant gas" in the analysis from cannel coal includes under one head the whole amount of the "heavy hydro-carbons" which impart richness and luminosity to the manufactured gas. The gas made from petroleum, when allowed to pass in a fine stream into a retort, previously heated red-hot, is particularly rich in these heavy hydro-carbons, as the following analysis exhibits: Heavy hydro-carbons. 33.4 . 40. 26. The specific gravity of this gas is 0.7. It has been estimated that 200 feet of this gas are equal in illuminating power to 1000 feet of gas made from coal, and it is so rich in the light-bearing element, carbon, that burners of special construction are needed in its use. On this account, in the manufacture of gas for illuminating in cities, small quantities of petroleum are sometimes used to impart richness to the product. In the manufacture of gas from coal, there come over the luminiferous constituents and the non-luminous supporters of combustion. The former include the hydro-carbon gases acetylene, olefiant gas, butylene and vapors of the benzole and naphthalene series; while the latter embrace hydrogen, marsh gas, and carbonic oxide. The chemist, Berthelot, made some experiments which are interesting in this connection. Formerly, it was the custom to regard the proportion of heavy carburetted-hydrogen (olefiant gas) as the measure of the illuminating power of gas. This chemist has shown, that in some samples of good luminous power, the proportion of olefiant gas is very small. They contain, however, from 3 to 4 per cent. of benzole vapor. It has been shown that a mixture of one volume of hydrogen and three volumes of ethylene yields only a little more light than pure marsh gas, while hydrogen when mingled with only 3 per cent. of benzole vapor will give a brilliant flame. The following table exhibits the various hydro-carbons, both gaseous and liquid, which are found either as components of, or are associated with, natural gas. Table showing the Properties of the chief Gaseous Elements of Natural Gas, and including some of the heavier Hydro-carbons. The recent improved methods for the utilization of coal as fuel by conversion into a gas before its introduction into the furnace, have opened the way for the use of natural gas into a great variety of industries. The great superiority of the improved method along with its economy prepared the minds of manufacturers to give this new form of fuel a fair trial. An analysis of the natural gas incontestably disclosed its great calorific power. The only obstacle in the way of its rapid and universal introduction was the uncertainty respecting the continued flow of the gas from the wells. As the alteration of the furnaces, to fit them for using the gas, often involved a large expenditure, it was reasonable to expect hesitancy in making the necessary changes. Its great advantages, however, in convenience of application, and its cheapness in comparison with every other form of fuel, gradually overcame every obstacle. Probably nowhere, has more attention been given to the scientific investigation of the subject than in the city of Pittsburgh, and certainly no more appropriate or more extensive field of operation could have been found. Natural gas, next to hydrogen, is certainly the most powerful gaseous fuel, and, when properly applied, the most economical, as we can obtain from it nearly all its theoretical heating power. In the manufacture of iron, its freedom from sulphur makes it peculiarly desirable as a fuel. The regularity of its supply under boilers makes the generation of steam an easy and certain thing, an important factor in the regulation of machinery. A committee of the American Society of Mechanical Engineers, to which the subject of the employment of the gas as a fuel was referred, recently made an interesting report to which we are indebted for valuable information. From this report we make the following extracts : "A large number of experiments have been made to ascertain the value of gas in comparison with coal, but as yet the method of delivery of the former and its mode of application are so crude that any accurate results have not yet been reached.1 "Consumers are not charged according to the number of cubic feet delivered, and no meters are employed. Previous estimates having been made as to the cost of coal in the manufacture of one ton of iron, gas is offered to the manufacturer at a price which will materially reduce his fuel bill and render it more economical in other ways for him to use it. Accordingly his bills are rendered to him, not according for the amount of gas consumed, but according to the output of the furnace. With this method of delivery of the gas it is hardly likely that manufacturers will study economy in its use, or go to much expense in the scientific adaptation of their furnaces with this end in view. It is to be hoped, however, that a better, wiser system will be adopted, which will remedy a reckless waste [Since the appearance of this report, such substantial improvements have been made in these particulars, that these statements must be materially modified.] of this valuable natural product. When it can be shown that by a simple contrivance of easy application, a factory could accomplish the same amount of work with the consumption of one-third of its present supply, consumers could not reasonably object to some form of meter being placed in their establishments provided rates were not increased. It is also quite reasonable to suppose that a more perfect and better regulated supply could be furnished at even less than present rates, which of course would in its turn invite a still larger demand. "In the estimation of the calorific power of any form of fuel, its chemical analysis is absolutely essential. The next thing to be considered, after obtaining the theoretical amount of oxygen necessary to obtain perfect combustion, is to arrange for the proper supply of atmospheric air. In the use of coal the frequent opening and closing of the furnace doors vitiates any calculation in this direction, and while the difficulties in this respect are greatly lessened by the use of gaseous fuel, it has been found in practice difficult so to adjust the pressure and flow of the gas as at all times to mingle it with just the proper amount of air to insure perfect combustion." Mr. Metcalf, of Pittsburgh, makes the following sensible observations on this head :— "There are three ways of getting at this combustion. The first is on the blowpipe principle with a strong blast of cold air and a heavy pressure of gas. This is a favorite and a stupid way. The second is what might be called 1 [Vide foot-note, page 217.] |