35 



attention from the chemist at the present time than those connected 

 with the production of india rubber or caoutchouc. An 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 6o,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 Landolphia 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 are 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 

 higher price than 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 and 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 from Brazil. 



The services which chemistry can render to the elucidation of 

 the problems of rubber production and utilisation are very nu- 

 merous. Methods of treatment depending 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 the addition of an acid, or sometimes of alkali, or even on 

 mere exposure, coagulation takes place and the rubber separates 

 as a solid, the other constituents for the most part remaining 

 dissolved in the aqueous liquid or ' serum.' The first view taken 

 of the nature of the coagulation process was that, like the coagu- 

 lation of milk by acids, it is, dependent upon 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 coagu- 

 lation 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 increased if access cannot 

 be had to fresh latex. A number of experiments were made at 

 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, 



