386 



PRINCIPLES OF CHEM1STKY 



obtained from those kinds of fuel which under ordinary conditions 

 burn without flame : for instance, anthracite, coke, charcoal. Heating 

 by means of a gas-producer that is, an apparatus producing carbonic 

 oxide from fuel is carried on in the same manner. 19 In trans- 

 forming one part of charcoal into carbonic oxide 2420 heat units 

 are given out, and 011 burning to carbonic anhydride 8080 heat units. 

 It is evident that on transforming the charcoal first into carbonic 

 oxide we obtain a gas which in burning is capable of giving out 5660 

 heat units for one part of charcoal. This preparatory transforma- 

 tion of fuel into carbonic oxide, or producer gas containing a mixture 

 of carbonic oxide (about ^ by volume) and nitrogen ( volume), in 

 many cases presents most important advantages, as it is easy to 

 completely burn gaseous fuel without an excess of air, which would 

 lower the temperature. 20 In stoves where solid fuel is burnt it is im- 

 possible to effect the complete combustion of the various kinds of fuel 

 without admitting ^n excess of air. Gaseous fuel, such as carbonic oxide, 



19 In gas-producers all carbonaceous fuels are transformed into inflammable gas. In 

 those which (on account of their slight density and large amount of water, or incom- 

 bustible admixtures which absorb heat) are not as capable of giving a high temperature 



in ordinary furnaces for instance, fir 

 cones, peat, the lower kinds of coal, &c. 

 the same gas is obtained as with the 

 best kinds of coal, because the water 

 condenses on cooling, and the ashes and 

 earthy matter remain in the gas-pro- 

 ducer. The construction of a gas-pro- 

 ducer is seen from the accompanying 

 drawing. The fuel lies on the fire-bars O, 

 the air enters through them and the ash- 

 hole (drawn by the draught of the chimney 

 of the stove where the gas burns, or 

 else forced by a blowing apparatus), the 

 quantity of air being exactly regulated 

 by means of valves. The gases formed 

 are then led by the tube V, provided 

 with a valve, into the gas main, U. The 

 addition of fuel ought to proceed in 

 such a way as to avoid the separation of 

 carbonic anhydride ; hence the space A 

 is kept filled with the combustible and 

 covered with a lid. 



20 An excess of air lowers the tem- 

 perature of combustion, because it be- 

 comes heated itself, as explained in 

 Chapter III. In ordinary furnaces the 

 excess of air is three or four timea 



greater than the quantity required for perfect combustion. In the best furnaces 

 (with fire-bars, regulated air supply, and corresponding chimney draught) it is necessary 

 to introduce twice as much air as is necessary, otherwise the smoke contains much car- 

 bonic oxide. 



FIG. 63. Gas-producer for the formation of carbon 

 monoxide for heating purposes. 



