1C)6 METHODS OF OBTAINING HIDROGEN GAS.

extinguished when immersed in it. It is therefore incapable ofsupporting combustion. It is not injurious to growing vegeta-bles. It is unabsorbable by most substances ; but water absorbsabout -jtj of its bulk. It is capable of dissolving carbon, sulphur,phosphorus, arsenic, and many other bodies. When its basiscombines'with that of oxigen gas, water is formed ;* with nitro-gen it forms ammonia. It does not act on earthy substances.It is decomposible by a great variety of bodies.

METHODS OF OBTAINING HIDROGEN GAS.

A ready method of obtaining hidrogen gas consists in subject-ing water to the action of a substance which is capable of de-composing this fluid.

1. For this purpose let sulphuric acid, previously diluted withfour or five times its weight of water, be poured on iron filingsor bits of zinc, in a small retort or gas-bottle, called a pneu-matic flask or proof; as soon as the diluted acid comes in contactwith the metal a violent effervescence takes place, and hidrogengas escapes without external heat being applied. It may be col-lected in the usual manner over water, taking care to let a cer-tain portion escape, on account of the atmospheric air containedin the disengaging vessel.

Rationale. ..The production of hidrogen gas is owing to thedecomposition of water. The iron or zinc, when in contactwith this fluid, in conjunction with sulphuric acid, has a greateraffinity to oxigen than the hidrogen has; the oxigen thereforeunites to it and forms an oxid of that metal which is instantlyattacked and dissolved by the acid ; the other constituent part ofthe water the hidrogen is set free, which by uniting with caloric

* Hence its n»me Hijrogtn which is derived from •uater, and yirzpxcI am bora.