PEROXIDE OF HYDROGEN. 



These analyses shew that the channel water contains 9 times as 

 much lime as the Mediterranean, but this can be accounted for, 

 as the water flows over a bed of chalk. The Mediterranean, 

 agaiiv contains twice as much magnesia and sulphuric acid as 

 the Channel. In addition to those constituents, distinct traces 

 of iodine and of ammonia were detected.* 



PEROXIDE OF HYDROGEN. 



Equivalent, 21U.5, or 17 on hydrogen scale ; formula H-J-2C), 

 or H0 2 . 



The second compound of hydrogen and oxygen is a liquid, con- 

 taining twice as much oxygen as water, and is a body possessed 

 of very extraordinary properties. It was discovered by Thenard, 

 in 1818, who prepared it by a long and intricate process. 



Preparation. The formation of the peroxide of hydrogen 

 depends upon the existence of a corresponding peroxide of 

 barium. The latter is obtained by calcining pure nitrate of 

 barytes at a high temperature in a porcelain retort, and after- 

 wards exposing the earth barytes or protoxide of barium, which 

 is left, in a porcelain tube heated to redness, to a stream of 

 oxygen gas, which the protoxide rapidly absorbs becoming pe- 

 roxide. Treated with a little water the peroxide of barium 

 slakes and falls to powder, forming a hydrate, of which the 

 formula is Ba O 2 + H O. Dilute acids have a peculiar action 

 upon this hydrate, w T hich will be easily understood, if the pe- 

 roxide of barium is represented as the protoxide united with an 

 additional equivalent of oxygen, or as Ba O + O. They com- 

 bine with the protoxide of barium, forming salts of barytes, 

 and the second equivalent of oxygen, instead of being liberated 

 in consequence, unites with the water of the hydrate, the HO 

 of the preceding formula, giving rise to HO + O or the pe- 

 roxide of hydrogen, which dissolves in the water. Although it 

 would be inconvenient to abandon the systematic name peroxide 

 of hydrogen for this compound, still it must be allowed that the 

 properties of the body, as well as its mode of preparation are 

 more favourable to the idea of its being a combination of water 

 with oxygen, or oxygenated water, as it was first named by its 

 discoverer, than a direct combination of its elements. It is re- 



* Phil. Mag. 3rd Scries, vol. 15, page 58. (1839.) 



