55. Is hydrogen found elsewhere?
It is never found but in a state of combination; united with oxygen, it exists in water; with nitrogen, in ammonia; with chlorine, in hydro-chloric acid; with fluorine, in hydro-fluoric acid; and in numerous other combinations.
56. Is the gas used to illuminate our streets, hydrogen gas?
It is; but it is combined with carbon, derived from the coals from which it is made. It is therefore called carburetted hydrogen, which means hydrogen with carbon.
57. How is hydrogen gas obtained from coals?
It is driven out of the coals by heat, in closed vessels, which prevent its union with oxygen.
58. What becomes of the water which is formed by the burning of hydrogen in oxygen?
It passes into the air in the form of watery vapour. Frequently it condenses, and may be seen upon the walls and windows of rooms where many lights or fires are burning. Sometimes, also, portions of it become condensed in the globes of the glasses that are suspended over the jets of gas. A large volume of these gases forms only a very small volume of water.
59. What becomes of the carbonic acid gas which is produced by combustion?
It is diffused in the air, which should be removed by adequate ventilation.