The Romance of Modern Chemistry

MORE ABOUT FUEL duced. The chemical reaction involved is very simple; the water is decomposed by the red-hot carbon, and the latter appropriates the oxygen, forming carbon monoxide. The hydrogen of the water is left in the free state, and issues from the filmace along with the carbon monoxide. Since both these gases are combustible, the reader will perceive that the simple passage of steam over red-hot carbon means the conversion of a solid into a gaseous fuel. The product is called “ water gas,11 a term which must be carefully distinguished from “ water vapour11; the latter is of course not combustible. Simple as the foregoing process may seem to be on paper, many difficulties were experienced in making it work on a large scale. The decomposition of steam by carbonaceous fuel requires a large amount of heat, and it was soon found impracticable to supply this by external heating of the retorts containing the coke or coal. The device was accordingly adopted of heating the fuel inter- nally by its partial combustion. Air is blown into the retort containing the ignited fuel, which is raised to incandescence by the heat given out in its own com- bustion ; then, as soon as this condition is attained, the air blast is shut off and steam is blown into the retort. The formation of water gas at once begins, and is con- tinued until the temperature falls below a certain limit, when the steam blast is shut off and air is once again blown in. It must be understood that the two parts of this operation, the air blow and the steam blow, are complementary to each other, the heat evolved in the first stage supplying the energy required in the second stage. Water gas, this mixture of hydrogen and carbon monoxide, burns with a non-luminous flame, and, if it is 151