Discovered by Fontana, in 1780, and first worked by Ibbetson, in England, in 1824, water gas has added a voluminous chapter to the patent records of England, France, and America, no less than sixty patents being taken out between 1824 and 1858, in which the action of steam on incandescent carbon was the basis for the production of an inflammable gas.
Up to the latter date the attempts to make and utilize water gas all met with failure; but about this time the subject began to be taken up in America, and the principle of the regenerator, enunciated by Siemens in 1856, having been pressed into service in the water-gas generator under the name of fixing chambers or superheaters, we find water gas gradually approaching the successful development to which it has attained in the United States during the last ten years. Having now, by the aid of American skill, been brought into practical form, it is once more attempting to gain a foothold in Western Europe—the land of its birth.
When carbon is acted upon at high temperatures by steam, the first action which takes place is the decomposition of the water vapor, the hydrogen being liberated, while the oxygen unites with the carbon to form carbon dioxide:
| Carbon. | Water. |
| C + | 2H2O = CO2 + 4H2 |
And the carbon dioxide so produced interacts with more red-hot carbon, forming the lower oxide—carbon monoxide:
CO2 + C = 2CO
So that the completed reaction may be looked upon as yielding a mixture of equal volumes of hydrogen and carbon monoxide, both of them inflammable but non-luminous flames. This decomposition, however, is rarely completed, and a certain proportion of carbon dioxide is invariably to be found in the water gas, which, in practice, generally consists of a mixture of about this composition:
| WATER GAS. | |
|---|---|
| Hydrogen | 48.31 |
| Carbon monoxide | 35.93 |
| Carbon dioxide | 4.25 |
| Nitrogen | 8.75 |
| Methane | 1.05 |
| Sulphureted hydrogen | 1.20 |
| Oxygen | 0.51 |
| ——— | |
| 100.00 | |
The above is an analysis of water gas made from ordinary gas coke in a Van Steenbergh generator.
The ratio of carbon monoxide and carbon dioxide present entirely depends upon the temperature of the generator, and the kind of carbonaceous matter employed. With a hard, dense anthracite coal, for instance, it is quite possible to attain a temperature at which there is practically no carbon dioxide produced, while with an ordinary form of generator and a loose fuel like coke, a large proportion of carbon dioxide is generally to be found.