ON THE PRESENT POSITION OF THE CHEMISTRY OF RUBBER, 251 



-derivative, which on analysis was found to be CioHisBrj. The authors 

 suggested that the compound C,oH,,iBr,; was first formed, and that then, 

 by the splitting off of hydrogen bromide, this passed into CioHijBrs. 

 The caoutchouc tetrabromide C,oH||,Br, was afterwards prepared and 

 examined by C. O. Weber.' He found that it was best obtained by slowly 

 dropping bromide into a well cooled solution of pure rubber in chloroform 

 until slight excess of Br was present, afterwards running the solution in 

 a fine stream into alcohol, which precipitates the Ijromide in fine white 

 flakes. These were filtered, washed on the filter with alcohol, and dried 

 below 40^ C. At 60° C this tetrabromide begins to decompose, HBr is 

 given ofF, and the colour becomes darker. Caoutchouc tetrabromide is 

 fairly soluble in the cold in chloroform, and in thiophenol, but insoluble 

 in most organic solvents On heating it is soluble in pyridine and 

 piperidine, but the solution is attended by the loss of HBr. 



Boiling alcoholic potash has little efiect upon it, but on treating with 

 sodium ethylate in a closed tube the bromine is gradually though 

 not completely removed, and, to some extent, ethoxyl groups are 

 substituted. Oxidising agents, such as nitric and sulphuric acids, afiect 

 it very slowly. When treated with phenol, hydrogen bromide was evolved 

 and a substance formed which on analysis gave figures correspond- 

 ing with those calculated for a tetroxyphenyl-polypi'ene of the formula 

 C,oH,6 (OCeHs),. 



C,oH,6Br, + 403H,OH=C,oH,«(OCeH5), + 4HBr. 



By varying the conditions of the preparation other derivatives were 

 obtained containing more oxygen than is indicated in the above formula ; 

 e.g., C,oH,60,(OC,3H.3), and Q,,-K,,0,{QC,n,),. On treatment with 

 aqueous or alcoholic soda these bodies split off phenol. Other phenols 

 and naphthols were found to act in a similar manner on the tetrabromide. 



Gladstone and Hibbert considered that iodine had very little action 

 upon rubber dissolved in chloroform, but Weber found that on treating 

 such a solution with a large excess of iodine an unstable straw-coloured 

 product was obtained, which gave analytical figures agreeing with the 

 formula (CioHioIs),. 



Weber also investigated the action of hydrochloric acid upon 

 caoutchouc in chloroform solution. He found that when dry hydrogen 

 chloride gas was used the product was an indefinite sticky substance, but 

 that if the gas were moist a white friable substance was obtained, readily 

 soluble in chloroform, but almost insoluble in most other solvents. Its 

 analysis agreed fairly well with the formula CioHigOla- It dissolved in 

 organic bases, but apparently with the loss of HCl. 



Hydrobromic acid yields with caoutchouc a very unstable substance, 

 which Weber was unable to obtain in the pure state. 



Uydriodic acid. — Berthelot ^ stated that on treating indiarubber with 

 hydriodie acid at 280° C. hydrocarbons of the paraffin series, boiling with- 

 out decomposition above 350° C, were produced. 



Action of Nitric Acid upon CaoutcJiouc. 



F. C. Achard ^ found that nitric acid acted on caoutchouc, with the 

 production of a yellow colour and evolution of NO2, CO^, and HON, 



» Chemistry of Indiarubber, 1902, p. 31. ^ Bull. Soo. Chim., 11, 33. 



' GmeliD, Handb. d. Chem. (1866), 7, ii. 1763. 



