30 THE ROYAL SOCIETY OF CANADA 



under pressure. That is, the chlorine content fell to below that 

 corresponding to the formula CioHieHCl. This was one of the obser- 

 vations which led Harries to an expression of a marked loss of con- 

 fidence in a C10H16 formula of rubber which he had advocated for 

 many years. I will consider this formula presently. 



At this stage of the development of rubber chemistry this action 

 of halogens and of halogen acids was accepted as proof that the 

 rubber molecule, consisting of CioHie groups associated together, is 

 unsaturated, each C oHic containing two pairs of unsaturated carbon 

 atoms. 



Other work had also been performed on iodine derivatives and 

 upon the action of nitrogen tri-oxide upon rubber yielding the so-called 

 nitrosites. However, these did not contribute anything to the 

 problem of constitution. 



This, brieffy. was the condition of this problem prior to the year 

 1910. During this year Lebedew (18) published a paper upon the 

 products of the action of ozone upon some diethylenic hydrocarbons 

 and the products of these so-called ozonides upon decomposition with 

 steam. This work, which was substantiated and expanded greatly 

 by Harries (19), threw a flood of light upon the constitution of rubber. 

 Briefly, it was found that diethylenic compounds when acted upon 

 by ozone add on three atoms of oxygen at each double bond, and the 

 subsequent decomposition of these ozonides yield aldehydes and acids 

 related in a very clear way with the original diethylenic compounds, 

 so that by preparing the ozonides in the case of similar compounds 

 and isolating the products upon hydrolysis it should be possible to 

 derive their constitutions. 



This was done by Lebedew and Harries. It was found that the 

 product obtained when a chloroform solution of rubber is treated 

 with ozone, formed, when decomposed by steam, laevulinic aldehyde, 

 laevulinic aldehyde peroxide and laevulinic acid. These investigators 

 concluded that rubber diozonide has the constitution: 



f>^3 



CH^-CH-Ç-CHp 

 0-0-0 I 

 0-0-0 I 



CH3 



