ON THE PRESENT POSITION OF THE CHEMISTRY OF RUBBER. 237 



The vapour density indicated the formula to be CjoHig, and it gave 

 on analysis the following figures : — 



C - 8700 per cent. H = 11-56 per cent. 



Calculated ° for C,„Hi5. 



C = 88-23 „ H = 11-77 



Himly also described chlor-caoutchine obtained by passing chlorine 

 into the cooled hydrocarbon, and also the caoutchine hydrochloride ob- 

 tained by the action of dry hydrochloric acid gas on cooled caoutchine. 



The most complete investigation of this period on the distillation 

 products of rubber was that made by Alexander Bouchardat, and pub- 

 lished in 1837 in the 'Journal de Pharmacie' (vol. xxiii. 1837). 



The object of the investigation was the discovery of a good solvent for 

 indiarubber. Bouchardat distilled his rubber from a copper retort fitted 

 with a curved neck which terminated in a spiral condenser. This was 

 surrounded by ice, and communicated at the base with a series of three 

 bottles immersed in a freezing mixture. By distillation in this apparatus 

 417 grs. of rubber yielded (a) 357 grs. of liquid, collecting in the first 

 flask, and {b) 29-82 grs. in the other two flasks. 



Hevdene. 



From the liquid in the first flask Bouchardat isolated a hydrocai-bon 

 boiling at 252° C, to which he gave the naraeheveene (from Hevea guian- 

 ensis, a euphorbiaceous rubber-yielding tree). This is a transparent, neu- 

 tral yellow oil, having a specific gravity -921 at 16-8°, and boiling point 

 about 252°. It does not solidify at low temperatures, burns with a smoky 

 flame, and is soluble in absolute alcohol. The composition in two experi- 

 ments was found to be : — 



1. C = 86-62 H = 13-18 



2. C = 85-24 H = 14-76 



This substance forms a wax-like derivative when chlorine is passed 

 over it, hydrochloric acid being at the same time evolved. Bromine and 

 iodine compounds were also obtained, but evolution of HBr or HI 

 always accompanied the formation. When treated with strong caustic 

 potash or soda heveene becomes viscous and discoloured owing to oxygen 

 absorption. On slowly adding strong sulphuric acid to heveene in a 

 stoppered flask — with frequent cooling — Bouchardat obtained a thick 

 brown mass, and noticed that after standing a few days a clear oily 

 liquid floated on the top. This oil was separated, washed, purified, and 

 finally distilled. It boiled at 182° -4, was soluble in alcohol and ether, and 

 was unacted upon by concentrated alkalies and acids. 



Bouchardat considered it to be identical with the product obtained by 

 Gregory by treating the light oil (boiling-point 35°-77°) with sulphuric 

 acid, although Gregory's product boiled at 226° C. 



On examining the liquid contained in the second and third flasks, it 

 was found to be a transparent, mobile, slightly yellow liquid, which boiled 

 a few degrees above freezing-point. A portion crystallised out at —25° C, 

 but the other part of the liquid would not solidify at —30°. A partial 

 separation was thus effected : (a) the mother liquid was run oS" and 

 examined first. On acting upon it with sulphuric acid, heat was deve- 

 loped, and after standing for a few days a clear transparent oil separated 



