50 HYDROGEN. 



irfals, when obliged to breathe in it, die almost in- 

 stantaneously. It has a peculiar and disagreeable 

 smell. 



It is decomposed by living vegetables, and its 

 base is one of the constituents of oil, resin, &c. 

 It is highly inflammable, and burns rapidly when 

 kindled in contact with atmospheric air, or oxygen 

 gas, by means of the electric spark, or by an in- 

 flamed body, exhibiting a blue lambent flame. 

 Water absorbs about one thirteenth of its bulk. 

 It dissolves carbon, sulphur, phosphorus, arsenic, 

 and many other bodies. When its basis combines 

 with that of oxygen gas, water is formed, and with 

 nitrogen it forms ammonia. 



An easy method of obtaining hydrogen gas 

 consists in subjecting water to the action of a 

 substance which is capable of decomposing this 

 fluid. 



For this purpose, let sulphuric acid, diluted 

 with four or five times its weight of water, be 

 poured on iron filings or bits of zinc, in a small 

 retort or glass bottle ; as soon as the diluted acid 

 comes in contact with the metal, a violent effer- 

 vescence takes place, and hydrogen gas escapes, 

 without external heat being applied. It may be 

 collected in the usual manner over water, taking 

 care to let a certain portion escape, on account 

 of the common air contained in the disengaging 

 vessel. 



Hydrogen gas is often found in great abundance 

 in mines and coal-pits, where it is sometimes gene- 

 rated, and becomes mixed with the atmospheric air 

 of these subterraneous cavities. If a lighted can- 

 dle be brought into this mixture, it explodes, and 

 produces the most dreadful effects. It is called by 

 miners the Jire damp. It generally forms a cloud 



