124 PARA RUBBER, 



The sample from Ceylon was valued at 5s. l\d. per lb., and the 

 report stated that the rubber was free from moisture, very strong, 

 and vulcanized well. The sample from the Bukit Rajah Co. was 

 considered to be very suitable for vulcanization, and sold at a little 

 over 7 francs per pound. The Penang sample was prepared in 

 rectangular cakes, was dark brown in colour, transparent, and 

 contained no mechanical impurities ; one piece was sticky. The 

 value was considered to be equal to the current market rate of 

 good Para. 



The samples from the Gold Coast were considered to be of ex- 

 cellent quality, free from mechanical impurities, and in February, 

 1904, were valued at 4s. 6d. to <ks. Id. per lb. The old sample of 

 Straits rubber had been kept in Ceylon for a considerable length 

 of time. 



The high percentage of caoutchouc in Para rubber, grown in 

 different countries, is so far very satisfactory. Johnson has shown 

 that whereas the cultivated Para may contain over 95 per cent, of 

 caoutchouc and less than 4 per cent, of resinous matter, the native 

 African rubber ( Funtumia elastica) contains less than 90 per cent, 

 of caoutchouc and over 8 per cent, of resinous compounds. From 

 the foregoing analyses and valuations it may safely be asserted 

 that Hevea brasiliensis bids fair to beat many rubber trees indigenous 

 to tropical areas. Resins in large quantities, albuminoids, and ash 

 constitutents are not required, and in many articles of commerce 

 are injurious. 



Resins. — In Para rubber the amount of resinous and oily substan- 

 ces varies from 1 to 4 per cent., when obtained from mature trees. 

 Many analyses have been made of rubber from trees of various 

 ages and of different species. In the case of Castilloa elastica, 

 Weber* proved that not only does the percentage of resin decrease 

 with the age, but that it increases as one passes to younger parts 

 of the same tree. His figures were as follows :- 



Resins in Rubber of Castilloa Trees. 



From Per cent. 



Trunk 

 Largest branches 



Medium 



Young 



Leaves 



2-61 

 3-77 



4-88 

 5-86 

 7-50 



A similar increase in resin in the rubber from young Castilloa 

 trees of different ages was also described, the variation being from 

 721 per cent, from eight-year-old trees to 35-02 in rubber from 

 trees three years old. 



Weber concluded that it could scarcely be doubted that rubber 

 rom other kinds of rubber trees would exhibit similar relationships ; 



* Weber, India Rubber and Gutta Percha Trades Journal, Sept, 29, 

 1902. 



