254 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1912. 



as muck that is untrue and misleading has appeared m the press 

 during the last few weeks. 



But first, a few words about natural rubber. The Old World owes 

 its knowledge of this substance to the New. This wonderful product 

 became known in Europe shortly after Columbus discovered Amer- 

 ica. If I, comuig from across the ocean, now bring you this colloid 

 prepared there synthetically, I merely repay part of the debt which 

 we owe America. 



Hardly a generation ago, the southern part of this great American 

 continent furnished the whole supply of the different kinds of rubber. 

 Since then extensive plantations of rubber trees have been established 

 in various tropical countries, and then* yield has grown so enormously 

 that the old home of wild rubber will soon bo thrust into the back- 

 ground. This is a matter which involves many millions; conse- 

 quently a very serious economical problem confronts South America. 



You all knov/ that caoutchouc is made from the milky sap of 

 numerous species of trees and shrubs and the grotesquely formed 

 lianas by various coagulation processes, and that this product, on 

 being suitably treated with sulphur or sulphur compounds, i. e., by 

 vulcanization, acquires its valuable and characteristic properties. 

 The synthetic method took quite a different route. By breaking up 

 tho very complex molecule which rubber doubtless possesses, by 

 pyrogenetic processes, i. e., by dry distillation, a veritable maze of 

 all kinds of gases, oils, and resins was obtained, as well as a colorless 

 fluid resembling benzine, to which the investigators gave the name 

 "isoprene." It was Bouchardat who first expressed the belief that 

 this isoprene, which is obtained in veiy small quantities and in an 

 impure form by the dry distillation of caoutchouc, might be closely 

 and intimately related to caoutchouc itself. This important question 

 was then eagerly discussed for several decades by the scientists of all 

 countries, and opinions were sharply divided. 



As far back as the eighties, Tilden claimed to have prepared arti- 

 ficial rubber from isoprene by treatment with hydrochloric acid and 

 nitrous acid. But neither Tilden nor his assistants, though they 

 worked strenuously for years, succeeded in repeating the experi- 

 ments. Moreover, numerous other investigators, among them our 

 chemists, were unable to confirm the results. In 1S94 Tilden found, 

 however, that that isoprene which ho had prepared about 10 years 

 before, on standing, had partially polymerized into rubber. In this 

 way Tilden, in fact, was the fu-st discoverer of synthetic rubber. But 

 this method which time has not yet permitted to repeat is obviously 

 not a commercial one. Dr. Fritz Hofmami of the Farbenfabriken 

 vorm. Friedi*. Bayer «fe Co. is to be regarded as the real inventor of 

 synthetic rubber, for, by the application of heat, he succeeded, as tho 

 first, in August, 1909, in polymerizing tho isoprene molecules com- 



