130 



(March 1907. 



GUMS, RESITS, SAPS, AND EXUDATIONS. 



THE PRODUCTION OF INDIA RUBBER. 



From the Opening Address by Prof. Wyndham Dunstan at the 



British Association. 



[So much discussion, based on imperfect reports, has taken place on this subject, 

 that we think it well, even at this late date, to reproduce the exact report —Ed. " T. A."] 



There is no more important group of questions demanding attention from 

 the chemist at the present time than those connected with the production of india- 

 rubber or caoutchouc. ,4n enormous increase in the demand for india-rubber has 

 taken place in the last few years, and last year the production was not less 

 than 60,000 tons. Until recently the supply of rubber came chiefly from two 

 sources— the forests of Brazil, which contain the tree known as Hevea brasiliensis, 

 furnishing the Para rubber of commerce which commands the highest price, and the 

 forests of Africa, where climbing plants, generally of the Laudolpnia class, also 

 furnish rubber. The increased demand for caoutchouc has led to the extensive 

 planting of the Para rubber tree, especially in Ceylon and in the Federated Malay 

 States. Systematic cultivation and improved methods of preparation * re responsible 

 for the fact that the product of the cultivated tree, which begins to furnish satis- 

 factory rubber when six or seven years old, is now commanding a higlser price tha n 

 the product of the wild tree in Brazil. It is estimated that within the next seven 

 years the exports of cultivated india-rubber from Ceylon aud the Federated Malay 

 States will reach between ten and fifteen million pounds annually and that after 

 fifteen years they may exceed the exports of the so-called wild rubber rom Brazil. 



The services which chemistry can render to the elucidation of the problems of 

 rubber production and utilization are very numerous. Methods of treatment depend- 

 ing on a knowledge of the other constituents of the latex have led to the production of 

 rubber in a purer condition. Much still remains to be elucidated by chemical means 

 as to the nature of the remarkable coagulation of the latex. As is well known, the 

 latex is a watery fluid resembling milk in appearance which contains the rubber, or, 

 as I think more probable, the immediate precursor of rubber, together with proteids 

 and other minor constituents. The constituent furnishing rubber is in suspension, 

 and rises like cream when the latex is at rest. On tne addition of an acid, or some- 

 times of an alkali, or even on mere exposure, coagulation takes place ;and the rubber 

 separates as a solid, the constituents for the most part remaining dissolved in the 

 aqueous liquid or " serum." The first view taken in the nature of the coagulation 

 process was that, like the coagulation of milk by acids, it is dependent open a process 

 of proteid coagulation, the separated proteids carrying down the rubber during 

 precipitation. 



This explanation cannot, however, be considered complete by the chemist, 

 and there are peculiarities connected with the coagulation of the latex which are 

 opposed to the view that it is wholly explained by the coagulation of the associated 

 proteids. The experimental investigation of the question on the chemical side is beset 

 with many difficulties which are iucreased if access cannot be had to fresh latex, A 

 number of experiments were made in the Imperial Institute with latex forwarded 

 from India. The difficulties contended with in preventing coagulation during transit 

 were great, but in the case of the latex derived from certain plants these were 

 to some extent surmounted, and the results obtained, especially with reference to 

 the behaviour of certain solvents towards the latex, led to the co elusion that 

 " coagulation" can take place after removal of the proteids, and that i probability 



