WATER GAS. 341 



Through the center of the furnace is a fire-clny partition, which extends 

 nearly to the top, and in this a coil of iron pipe. In working, a quantity of wood 

 and coal is introduced into the gasogens ; the doors are luted and the coal open- 

 ings on the top closed, but the upper end of the standpipe is allowed to remain 

 open to serve as a chimney. The blast is turned on till the wood is all burnt up, 

 and judging from the color of the flame issuing from the standpipe the mass of 

 coal has become incandescent. The blast is then shut off, steam is let in, and the 

 lid of the standpipe is closed. The steam, which is generated in immense boilers 

 at a high pressure, enters the coil of pipe contained in the fire-clay partition, 

 where it is superheated, and then enters the mass of incandescent coal through a 

 row of openings just above the grate bars. When the steam comes in contact with 

 red-hot coal, the following chemical reaction -takes place: H20-|-C=CO-j-H2. 

 Besides the carbonic oxide and hydrogen, some CH^, CO2 and HjS are formed, 

 and possibly other gases resulting from any impurities which may be contained 

 in the coal. The pressure caused by the generation of these gases force them up 

 the standpipe and over through a water seal into the main pipe; from here the 

 gas enters a small holder, which acts as a governor, causing a steady flow of gas 

 into the carburetters. The carburetters, which are situated at some distance from 

 the gasogens, consist of ten or a dozen shallow trays, arranged one above anoth- 

 er and surrounded by a steam jacket. A slow stream of naphtha, about five gal- 

 lons to the 1000 cubic feet of gas, is allowed to run into the top one; when this 

 gets full it overfTovvs through a small pipe into the next lower, and so on. The 

 heat of the steam in the jacket keeps the naphtha evaporating, and the vapors are 

 taken up by the gas, which enters at the bottom, and after passing back and forth 

 over the trays goes out at the top, and from thence to the retorts. These are 

 about twenty feet long, of the same shape and arranged in the same manner 

 as those used in the manufacture of coal gas; and they have perforated 

 partitions across them in order to retard the flow of gas. These retorts 

 are kept at a red heat. The gas enters at one end through pipes provided with 

 .valves for regulating the quantity, and passes out through a standpipe at the 

 other end. The object of passing the gas through these retorts is to "fix " the 

 naphtha vapor so that any lowering of the temperature will not cause a conden- 

 sation of the illuminating constituents. In order to determine how well this is 

 being accomplished the following simple test is used, which was patented in 1877 

 by Mr. H. C. Bowen : 



A slip of white paper is held in front of a small stopcock attached to the 

 standpipe ; on opening the stopcock a small stream of gas strikes the paper, caus- 

 ing a stain, from the color of which the workman is enabled to decide whether 

 the temperature of the retort is right. A brown stain is desired; if it is too dark 

 it indicates that the temperature is too high, and more gas is let in ; while if it is 

 too light in color the reverse is the case, and some of the gas is turned off. 



From the retorts the gas goes to the exhauster, which forces it through the 

 condensers, scrubbers, purifiers, meters, etc., into the holders, where it is stored 



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