140 PARA RUBBER. 



But it has been previously shown that in the Amazon District trees 

 are tapped when they are 15 years old, and when forest Para rubber 

 trees are 25 years old they are described as having reached maturity. 

 In view of these facts it is interesting to reflect on the chemical 

 analyses of rubber from trees 4, 6, 8, 10-12, and 30 years old, given 

 elsewhere. These analyses have been made from rubber obtained 

 from Ceylon-grown trees, and it is fortunate that the age can 

 be guaranteed. They show very clearly that the variation in chem- 

 ical composition between the rubber from young and 30-year-old 

 trees is insignificant, and that the reputed defects of rubber from 

 young trees cannot be explained from the differences in the chemical 

 analyses given. There is as much variation between the chemical 

 composition of samples of rubber from trees of the same age as be- 

 tween those given for the material obtained from trees 4 to 30 years 

 old, and the ordinary analytical methods do not appear to give indi- 

 cations of the great differences in physical properties. From these 

 and other considerations one feels compelled to seek for some other 

 tests, of a physical nature, whereby the rubber may be scientifically 

 classified, and which will allow of the value being calculated on a 

 sound basis. Colour cannot be accepted as a guide, though prefer- 

 ence seems to be given to the pale amber colour by many manu- 

 facturers ; only in the case of really bad samples can odour be taken 

 as indicating quality , as the best biscuits have often a cheesy putres - 

 cid smell which is more or less transient. In this chapter it will 

 be seen that certain physical tests have been devised, and the results 

 obtained with samples of Plantation rubber from the East are given. 

 It is not impossible that the physical properties of rubber will ulti- 

 mately be associated with the quantity and nature of the ingredients 

 indicated in the numerous chemical analyses which have been t quoted . 

 At the present time the valuation of different kinds of Plantation 

 rubber is not usually based on chemical analysis, except by a few 

 firms on the continent of Europe, but mainly on appearance and 

 physical characters. 



The "India Rubber Journal" of August 28 published a series of 

 reports regarding various samples of Plantation rubber from the 

 East. Opinions as to the strength and general value of cultivated 

 rubber have shown considerable variation, and though the 

 conclusions embodied in the previous paragraph may be taken as 

 representing the opinions of a large number of manufacturers, it has 

 frequently been stated on good authority that cultivated Para rubber 

 was equal in tensile strength to native-cured Para, and after vulcaniza- 

 tion gave very good results. The differences in strength noticeable 

 in Plantation rubber are usually ascribed to the tapping of young 

 trees and irregularity in mixing the latex from trees of different ages ; 

 the latter cannot help but occur on small estates, where only a small 

 proportion of the trees are even ten years old. 



Regarding certain samples of Plantation rubber it has been stated 

 that when worked on the mill the fight coloured samples gave the 

 odour peculiar to fine Para when prepared without the use of smoke. 



