XV 



THE MOLECULAR THEORY 



345 



" I write the two series of numbers, expressing these 

 weights in the following manner : 



The table shows amongst other things, " that the same 

 substance in its different allotropic forms can have different 

 molecular weights," but the data for " electrised oxygen " 

 are incorrect, the actual densities of ozone being 24 and 48 

 instead of 64 and 128. 



Oxygen as a standard of molecular and atomic 

 weights. In Cannizzaro's table, the hydrogen atom = i 

 and the hydrogen molecule = 2. The relative density of 

 oxygen is given as 16 and its molecular weight as 32. 

 Later experiments have shown that the exact figures are 

 i5'88 and 3176. 



In recent years, in accordance with a suggestion made by 

 Stas, the half-molecule or atom of oxygen has been adopted 

 as a standard of molecular and atomic weights, its weight 



