55 
cuts, and a total of two fluid ounces were obtained. Addition of a 
measured amount of ammonia caused the 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 77-72% 
100= 
Analysis of the pure latex gave : 
("Rubber 
7.83% 
Coagulum 
35-74% 
] Resin 
2778% 
(Ash 
0 . 13 % 
Serum Solids 
4-43% 
f Organic matter 
(Ash 
3-78% 
0 . 65 % 
Water 
59-83% 
Water 
59-83% 
100 . 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. 
(b) 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.” 
