64 AMOUNT OF RESIN IN RUBBER 



Rubber obtained from trunk 



„ ,, ,, largest branches 



„ „ „ medium branches 



„ young branches 

 leaves 



Percentage of 

 resin present. 



2-61 

 3-77 

 4-88 

 5-86 

 7-50 



In this tree, therefore, the rubber prepared from the 

 trunk contamed the lowest percentage of resm, and there 

 was a gradual mcrease in the proportion of resin on 

 passing upwards to the leaves, the product from which 

 contained nearly three times as much resin as that from 

 the trunk. 



Beadle and Stevens examined a specimen of rubber 

 obtained from the stalks of the leaves of a Para tree and 

 found it to have the following composition : 



Per cent. 

 Caoutchouc . . . .78-67 



Resin 7-12 



Protein 1302 



Ash 119 



In this case also the product obtained from the leaves 

 was much more resinous than the rubber prepared from 

 the trimk of the tree. 



In connection with this point reference may be made 

 to an experiment conducted by Burgess to determine 

 the variation in the amount of resin in the rubber from 

 different parts of a Para tree. Three specimens of 

 rubber were prepared from the tree in the following 

 manner : (1) from a large root, (2) from the basal portion 

 of the trunk up to 2 ft. from the ground ; and (3) from 

 the trunk at a height of 20 ft. It was found in this 

 case that the proportion of resm was greatest in the 

 rubber from the root and least in that obtained at a 

 height of 20 ft. on the trunk. 



Protein. — The nitrogenous substances present in 

 latex and crude rubber are generally assumed to be 

 proteins, and their amount is calculated in the usual 

 way from the percentage of nitrogen. It is extremely 



