THE RUBBER INDUSTRY — GIBBONS 199 



laws, such as those of Avogadro and Gay-Lussac, and the laws of 

 definite and multiple proportions were known, present-day organic 

 chemistry did not exist. At that time substances derived from 

 natural living sources were generally assumed to be fundamentally 

 different from those of inanimate origin. 



Previous workers in chemistry had confined their attention chiefly 

 to those forms of matter which possessed definite critical criteria — 

 in other words, solids, liquids, or gases. The interrelationship of 

 pressure, volume, temperature, and change in weight as a result of 

 chemical reaction, were about the only criteria for studying chemical 

 reactions. 



Faraday (2) was the first to publish the ultimate analysis of rub- 

 ber, and the carbon-hydrogen ratio which he determined is used 

 today. At the time Faraday made his analysis, there was consider- 

 able activity in studying various organic materials, all of natural 

 origin. Dry distillation of organic substances or mixtures had come 

 into use as an experimental method for obtaining information re- 

 garding the constitution of complex substances, and rubber was one 

 of the natural substances which was studied in this way. 



Himley (7) in 1838 obtained two hydrocarbons from rubber; one 

 of them he called "Faradayn," and it may have been isoprene. 



Williams (22) in 1860 definitely identified isoprene as one of the 

 constituents resulting from the dry distillation of rubber and showed 

 that it had the same hydrogen-carbon ratio as rubber. 



The present accepted structural formula for isoprene was estab- 

 lished by Tilden (18) in 1884. 



Bouchardat (1) in 1875 and Tilden (19) in 1892 showed that 

 isoprene or its hydrochloride could be polymerized under certain 

 conditions to give a rubberlike substance; furthermore, he showed 

 that this rubberlike substance on dry distillation gave the same 

 volatile hydrocarbon as rubber. 



Aside from their historical interest these researches are impor- 

 tant because they form the basis of our present knowledge of the 

 manner in which rubber, or at least rubberlike substances, can be 

 obtained from synthetic materials — that is, by the polymerization of 

 compounds containing conjugated double bonds. 



Another scientific foundation stone of great importance to the 

 later development of theories of vulcanization was the work of 

 Gladstone and Hibbert (4) who in 1888 measured the refractive 

 index of rubber and concluded that it was unsaturated. This was 

 confirmed by their observation that rubber under the proper condi- 

 tions forms an addition compound with bromine. 



The scientific studies of rubber were for the most part independ- 

 ent of the industrial development during this period. Although 



