376 



GAS. 



compensates for its greater complexity, and 

 less rational application of heat, is an open 

 question. Theoretically, it is the most imper- 

 fect of the systems; practically, it seems to be 

 nearly or quite as good as any. Its expensive 

 apparatus is its worst point. Hydrogen or 

 water-gas is generated just as in the other pro- 

 cesses, by alternate admission of air and steam 

 into the lower part of a cupola-furnace filled 

 with incandescent anthracite. When air is ad- 

 mitted to blow up the coal, a valve on the top 

 of an outlet-pipe is opened, and the products 

 of combustion are suffered t j escape into the 

 air, burning with a blue flame, six or eight feet 

 high. All this heat goes to waste. After halt 

 an hour's blowing, air is turned off and steam 

 admitted. The flame escaping from the top of 

 the cupola quickly changes in appearance, be- 

 coming more voluminous and reddish. The 

 top valve is then closed, and the hydrogen 

 passes on through a water-seal into a small 

 gas-holder. From the gas-holder it goes to a 

 carbureter. This is an iron vessel resembling 

 in principle a Coffey's still. It is full of trays, 

 and naphtha, admitted through its top, pours 

 down within it from tray to tray. The sides 

 of the carbureter are double, and filled with 

 water, kept hot by steam. The gas, when car- 

 bureted, passes on to benches of retorts. The 

 retorts are what are known as through retorts. 

 They go completely through the furnace, form- 

 ing tire-clay pipes about 12 by 20 inches in size, 

 of shape usually. They are kept at a good 

 red heat, and the gas passing through them be- 

 comes fixed. With regard to the hydrogen- 

 holder, although we spoke of the gas going 

 to it, this was not absolutely correct. The 

 holder in question is usually very small, and 

 only acts as a compensator, taking in gas 

 sometimes for an excessive production of hy- 

 drogen, at other times remaining stationary, 

 or delivering a small amount. As the adjust- 

 ment of the carbureting process depends upon 

 the even delivery of hydrogen, the holder is 

 made single -lift to preserve uniformity of 

 pressure. 



It will be noticed that, in describing the 

 water-gas processes, nothing has been said of 

 the operations of condensing, scrubbing, or 

 purifying. As soon as the water-gas is made, 

 the distinctive peculiarities of the process end, 

 the subsequent treatment being identical with 

 that to which coal-gas is subjected. For this 

 reason, in the illustrations water-gas apparatus 

 alone is sHown. The gas is passed through 

 air or water condensers of any of the usual 

 well-known types, and then through washers 

 or scrubbers. The necessity for washing water- 

 gas would seem less than in the case of coal- 

 gas, as it contains no ammonia, yet it is done. 

 It is then purified by lime. 



In the Municipal process fuel is consumed in 

 three places under the boilers, in the gasogens, 

 and in the retort- Turn aces. In the Lowe pro- 

 cess one of these sources of expenditure of 

 fuel is cut off ; there are no retort-benches to 



be heated. Theoretically, it is the more per- 

 fect process of the two. 



The trouble with water-gas is the production 

 of naphthalene. Fortunately, this does not 

 go outside of the works, and it is disposed 

 of there in various ways. It is dissipated 

 by steam, or is dissolved in naphtha, and thus 

 pumped out of the siphons. A strong solution 

 of naphthalene is sometimes obtained, that de- 

 posits on evaporation large quantities of the ob- 

 noxious crystals in a solid mass. 



Other methods have been devised for the 

 production of this gas, but the principal types 

 follow the ones described. Retort processes 

 have been used to some extent. In these, an- 

 thracite coal is charged into retorts, heated by 

 a fire just as in ordinary coal-gas making, and 

 steam is passed through, becoming decom- 

 posed into hydrogen and carbonic oxide. The 

 direct heating, the best characteristic of the 

 water-gas process, disappears ; but for small 

 works such processes are quite available. 



With regard to the economy of the differ- 

 ent water-gas processes, they appear at the 

 present prices to have rather the advantage 

 over coal-gas. Yields varying from 35,000 to 

 50,000 cubic feet of gas per ton of anthracite 

 coal are claimed ; while four and a half to five 

 gallons of naphtha or raw petroleum are re- 

 quired to carburet 1,000 cubic feet. 



Wood-Gas. One works in New York has 

 adopted wood as one of its sources of gas. It 

 has the same objection that attaches to water- 

 gas it contains a large percentage of car- 

 bonic-oxide gas. As it is of very low illumi- 

 nating power, it has to be enriched with 

 naphtha. The process has been little used. 



To give some idea of the importance of 

 water-gas, it need only be said that in New 

 York alone something like 1,500,000,000 cubic 

 feet of it are made annually. Of this quantity, 

 nearly one third is carbonic oxide, so that its 

 practical harmlessness is pretty well proved. 



Other Gas Apparatus. The past few years have 

 witnessed the completion of some extraordi- 

 narily large gasometers, or gas-holders, as the 

 gas-engineer more correctly calls them. One 

 in London, the largest in the world, has a ca- 

 pacity of 5,500 r OOO feet; in New York there 

 is one at the Municipal Gas Company's works, 

 with a capacity of 2,000,000, and two at the 

 New York Gas-Light Company's, with a ca- 

 pacity of 1,500,000 each. The latter works 

 have also the largest station-metre, as far as 

 drum capacity is concerned, in the world. 

 Each revolution of the drum passes 3,000 

 cubic feet of gas. 



Gas-Stoves. This industry has developed, 

 even in this country, where gas is compara- 

 tively dear, into a business of considerable ex- 

 tent, and their construction has been improved 

 upon until they are as good in every respect as 

 coal-stoves. In England vast numbers of 

 them are in use ; but there several conditions 

 make their introduction easier. Gas is far 

 cheaper there than here, and coal is not so 



