CONDITIONS OF CHEMICAL CHANGE 

 THE THERMAL DECOMPOSITION OF OZONE 



By D. L. CHAPMAN, M.A. 



As the current views on the ultimate structure of matter have 

 been derived almost entirely from the study of the properties of 

 matter in a rarefied condition, it would seem to be probable that 

 the elucidation of the mechanism of chemical change can be best 

 accomplished by the exhaustive examination of the phenomena 

 which accompany interaction in the gaseous state. The import- 

 ance of studying the dynamics of chemical change under such 

 conditions has been realised and emphasised in the past by a 

 group of English chemists whose researches have brought to light 

 some striking and interesting facts. These facts have served to 

 demonstrate that in most chemical transformations — even in the 

 most simple — the processes are more complex than we should 

 be led to infer if only the initial substances and the final pro- 

 ducts of the change are considered. When we glance at the 

 hypotheses advanced in explanation of the facts, however, we 

 cannot help being struck by their great diversity. That such 

 diametrically opposite views can be held at the same time by 

 competent authorities is in itself indisputable proof that the 

 mechanism of chemical change is but imperfectly understood. 

 Even the dynamic law of mass cannot, as yet, be said to have 

 been established for gaseous changes ; the quantitative examina- 

 tion of the effect of so-called catalysts (which in most interactions 

 play an important, perhaps an essential, part) has been under- 

 taken only in a few isolated cases. Whether the remarkable 

 accelerative effect of moisture is proportional to its concentration 

 is unknown. That progress should be retarded by lack of 

 knowledge on such fundamental points is scarcely surprising ; 

 it is manifest that the essential quantitative information can only 

 be procured by a very complete investigation being made of the 

 conditions which affect the rates of a few simple chemical 



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