350 



SCIENTIFIC RECREATIONS. 



Boussingault permitted a thin stream of water to flow into a large 

 empty flask, and by this water the air was gradually driven out into a flask 



containing chloride of calcium and sulphuric acid r 

 which effectually dried it. This dry air then* 

 passed into a large tube inside the reverberatory 

 furnace, in which tube were pieces of caustic 

 baryta. Heated to a dull redness this absorbs 

 oxygen, and when the heat is increased to a 

 bright red the superabundant gas is given off. 

 Thus the oxygen was permitted to pass from 

 the furnace-tube into the receiving glass, and 

 so pure oxygen was obtained from the air 

 which had been in the glass bottle at first 

 (fig. 338). 



336. /hosphorus burning in o<ygen. 



HYDROGEN SYMBOL H ; ATOMIC WEIGHT i. 



HYDROGEN is abundant in nature, but never free. United with oxygen 

 it forms water, hence its name, "water-former." It is to Parcelcus that its 

 discovery is due, for he found that oil of vitriol in contact with iron 

 disengaged a gas which was a constituent of water. This gas was 

 subsequently found to be inflammable, but it is to Cavendish that the real 

 explanation of hydrogen is owing. He explained his views in 1766. 



Hydrogen is obtained in the manner illustrated in the cut, by means 

 of a furnace, as in fig. 339, or by the bottle method, as per fig. 340. The 

 first method is less convenient than the second. A gun -barrel or fire-proof 

 tube is passed through the furnace, and filled 

 with iron nails or filings ; a delivery tube is 

 at the farther end, and a flask of water boiling 

 at the other. The oxygen combines with the 

 iron in the tube, and the hydrogen passes 

 over. The second method is easily arranged. 

 A flask, as in the cut, is provided, and in it 

 some zinc shavings are put. Diluted sul- 

 phuric acid is then poured upon the metal. 

 Sulphate of zinc is formed in the flask, and 

 the hydrogen passes off. 



Hydrogen being the lightest of all known 

 bodies, its weight is put as I, and thus we are 

 relatively with it enabled to write down the 

 weights of all the other elements. Hydrogen 

 is fourteen-and-a-half times lighter than atmospheric air, and would do 

 admirably for the inflation of balloons were it not so expensive to procure 

 in such large quantities as would be necessary. Ordinary coal gas, however, 

 contains a great deal of hydrogen, and answers the same purpose. 



Fig. 337. Magnesium wire burning 

 oxygen. 



