S5 



cuts, and a total of two fluid ounces were obtained. Addition of a 

 measured amount of ammonia caused thj latex to become much more 

 fluid and turn a bright yellow in colour. It was filtered through a 

 very fine mesh silk gauze to remove dirt, and acidified with acetic 

 acid. It does not coagulate as easily as true Jelotong latex with any 

 of the ordinary coagulating agents. 



Analysis of the dry coagulum is : 



Rubber 22.28% 

 Resin 7772% 



100. 



Analysis of the pure latex gave : 



Coagulum . 



Serum Solids 

 Water 



35.74% 



4-43% 



59-83% 



100. 



r Rubber 



< Resin 

 (Ash 



< Organic matter 

 (Ash 



Water 



7.83% 

 27.78% 

 0.13% 



3.78% 

 0.65% 



59.83% 



100. 



The latex thus strongly resembles that of the allied Dyera tree. 

 The coagulum, which is rather stiff and brittle when the first exces- 

 sive amount of water has been removed, contains exactly the same 

 proportions of rubber and resin as in the Dyera Jelotong. The 

 serum solids and the resin are very similar, they may possibly 

 be identical. The resins have all the appearance of belonging to the 

 amyrin group of resin alcohols as do the true Jelotong resins. Some 

 of the chief differences between the two latices are : 



(a) The inferiority of the Alstonia rubber. The extracted 

 rubber, although it seems to be caoutchvouc, is much 

 inferior in strength and colour to Jelotong rubber. 



ib) Inferiority of Alstonia latex as regards ease of coagulation. 



(c) Tendency to turn bright yellow of the Alstonia latex. If 

 Jelotong rubber is adulterated with pieces of " pulai " it 

 often is possible to detect the same by the yellow colour. 

 On the other hand if a small quantity of the " pulai " 

 latex is added to the Dyera latex it would be quite im- 

 possible to detect it as the dry material of both latices 

 has exactly the same percentages of rubber and resin. 



"PURUB" JELOTONG. 



A specimen of Jelotong coagulated by means of " Purub " was 

 examined. This was a large hard ball, yellow outside and slightly so 

 on the inside. It was very hard and brittle and looked very un- 

 promising. The age was said to be about three months. It probably 

 contained some " Pulai." 



