OXYGENATED WATER. 41 



gen. If, again, we wished to form water by 

 uniting its constituent gases, we should find 

 that we must take eight parts by weight of 

 oxygen gas, and one of hydrogen, and that 

 no other proportion would succeed. From 

 these two experiments it would be manifest 

 that water, wherever or however formed, is 

 always the same substance, and is made up of 

 the same component gases in the same relative 

 proportions. If, again, we found a clear fluid, 

 having all the appearance and character of 

 water, and discovered, on analyzing it, that it 

 contained sixteen parts of oxygen by weight to 

 one of hydrogen, we should be immediately 

 justified in declaring, on this account alone, 

 that this was not water. Such a compound of 

 oxygen and hydrogen actually exists, and has 

 been called peroxide of hydrogen, or oxyge- 

 nated water. From the circumstance of its 

 possessing a different composition to that of 

 water, however like that fluid it may appear, 

 it is nevertheless a different substance. And 

 this would be, because the first law of chemical 

 combination declares that "the same chemical 

 compound must always possess a definite and 

 unalterable constancy of composition for the 

 same substance." 



" The converse of this rule, however, is not 

 so universally true; the same elements com- 



