75 



Owing to its high percentage of Nitrogen, producer gas can 

 only be used economically with a regenerative furnace and there- 

 fore is not capable of general appUcation. 



This Nitrogen is derived from the air used in the combustion 

 of the fuel so that to convert the fuel into a gas free from 

 Nitrogen it must be burned with some other body than air. 

 That body is water. 



When steam is passed over incandescent carbon it is decom- 

 posed with formation of carbon monoxide and hydrogen — thus 

 H,0+C=:CO+H, 



Of course a mass of incandescent fuel cools rapidly when steam 

 is blown through it so that the great problem in the production 

 of water gas has been how cheaply to keep the fuel at a high 

 temperature avoiding admixture of air. The latest process of 

 making water gas involves two distinct operations. In the first 

 a mass of fuel contained in a generator is raised to a high 

 temperature by means of an air blast ; a gas similar to ordinary 

 producer gas being formed. This gas is a bye-product in the 

 manufacture of water gas itself. 



When the fuel in the generator is sufficiently hot, the air blast 

 is stopped and the outlet by which the producer gas has escaped 

 is closed. Another outlet is opened and a blast of steam blown 

 through the heated fuel, a gas being produced consisting of equal 

 volumes of hydrogen and carbon monoxide, that is a gas com- 

 pletely combustible. 



The operation of opening and closing the various valves are 

 effected by moving one lever, the valves opening and closmg in 

 their proper order. When the fuel has become cooled by the 

 action of the steam the valves are reversed and the temperature 

 again raised by the air blast. 



Water gas can be produced at a cost of about 4d. per 1,000 feet. 



Burning with a non-luminous flame, water gas requires incan- 

 descent burners when used for illuminating purposes. For 

 household use it is in many respects superior to coal gas, e.g. 



(1) The flame is perfectly free from smoke since the gas 



contains no hydro-carbons. 



(2) Less heat of combustion. 



(3) Unhke coal gas it can be easily and completely freed 



from sulphur, so that the products of combustion are 

 less injurious to health and furniture than those of 

 ordinary gas. 



(4) It requires only about one-third as much ah for com- 



bustion as coal gas, therefore the atmosphere of a room 

 is less vitiated. 



