ON THE PRESENT POSITION OF THE CHEMISTRY OF RUBBER. 247 



300° C. were vigorously acted upon, became brown or red in colour, and 

 resins were produced. The fractions boiling above 300° C. gave a sandy 

 amorphous nitro-compound of the formula C,pHi2N.jO,;, which was 

 identical with the compound this author had previously obtained by the 

 action of nitric acid on rubber itself.' This compound will be refen-ed to 

 later. 



In this account of the various investigations on the distillation 

 products of rubber it has not been thought advisable to explain, in the 

 light of present knowledge, the probable composition of all the fractions 

 isolated by the various investigators. In such a distillate, consisting of so 

 many different substances, none of the fractions obtained are likely to have 

 consisted of quite pure substances ; some were certainly complex mixtures. 

 The following table ^ will give some idea of the compounds isolated which 

 are of seemingly definite composition. The accompanying table also 

 shows the different fractions isolated from time to time : — 



"With regard to the theoretical value of the investigations of the pyro- 

 genic decomposition of rubber as affecting our knowledge of the constitu- 

 tion of the rubber molecule, the following conclusions can be drawn : — 



(1) The rubber hydrocarbon is closely related to the terpenes, and 

 any formula expressing its constitution must also be explanatory of the 

 easy transition of this hydrocarbon into isoprene and dipentene. 



(2) The existence of the complex 



. CH3— C-C-C 



' Ber., p. 1401, 1902. 



^ See Ditmar, Der ipyrogene Zerfall des Kautsehuks, 1904. 



