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product was obtained, the analysis of which agreed with the 

 formula C 10 H 16 S 2 CL. Other compounds were also prepared con- 

 taining a much lower percentage of sulphur, and these seem to 

 throw some light on the question of the size of the rubber 

 molecule. For example a homogeneous product was obtained 

 containing only 4*8 per cent, of sulphur, and to explain its 

 constitution it is necessary to assume that the caoutchouc 

 molecule is at least C 50 H 80 . Weber eventually concluded that 

 the formula C 60 H 96 was within the range of possibility, and this 

 would yield a vulcanisation compound of the type (C 60 H a6 SCI) . 

 A large number of sulphur compounds are possibly formed 

 between these two limits, containing varying proportions of 

 sulphur, and Weber regarded these as corresponding to the 

 different degrees of vulcanisation which can be obtained with 

 rubber and sulphur or sulphur chloride. 



The formula C 10 H 1(i S 2 Cl 2 for the fully vulcanised compound, 

 is in accordance with the view that the indiarubber molecule 

 contains one double bond for every C 5 H 8 complex. Additional 

 evidence is provided by a consideration of the brom-derivative 

 of caoutchouc, especially if, in the preparation, care has been 

 taken to prevent substitution. Thus if bromine is added to 

 a cooled solution of indiarubber in chloroform until the brown 

 colour of the bromine just remains, and the solution is then 

 poured into alcohol, a parchment or rag-like substance is 

 precipitated which on analysis is found to have the formula 

 (C 6 H 8 Br 2 ) n . It was first prepared by Gladstone and Hibbert 1 

 in 1888 and afterwards examined by Weber, 2 who also prepared 

 and examined the hydrochloride (QH 8 • HCl) n . 



From a consideration of the physical properties of caout- 

 chouc, Gladstone and Hibbert, on the other hand, came to the 

 conclusion that for every C 10 H 16 there were three double bonds. 

 Some halogen derivatives were also prepared by them which 

 also seemed to support this conclusion, but the great bulk of 

 evidence is in opposition to this view. At the same time the 

 same two workers endeavoured to arrive at the molecular 

 weight of caoutchouc by the application of the Raoult method, 

 but the depression of freezing point observed was so small, that 

 if the method holds good in this case, the molecule must be 

 represented as at least C 10 ooH 100 o. 



1 Journ. Chem. Soc. 1888, p. 680. 



2 Chemistry of Indiarubber ( 1 902), p. 3 1 . 



