123 



PARA RUBBER. 



Para compared iviili Ficus, Urceta, and Rhynocodia Rubber. 



1 (5) (6) (7) (8) 



Species Ficus elastica Urceola Rhynocodia 



of Ficus. (Bengal). esculenta. Wallichii. 



per cent. per cent. per cent. per cent. 



Caoutchouc .. 19-6 .. 84-3 .. 80-5 .. 86-5 



Resin .. 49-9 .. 11-8 .. 9-8 .. 6-5 

 Dirt and insoluble 



matter .. 2-1 .. 3-1 .. 5-7 .. 4.2 



Ash included in dirt 0-79 .. 0-8 .. 1 • 1G 0.48 



Moisture .. 28-4 .. 0-8 .. 4-0 .. 2.8 



Valued at Valued at Valued at Valued at 



1 Id. per lb. 1/10 to 2/1 4/- per lb. 3/6 per lb. 



when Para when Para when Para in 1902 



at 4/8 at 4/8 at 4/8 



Though the various " Plantation " and " Wild " rubbers which 

 arrive in Europe contain resin in quantities varying from 1 

 to about 40 per cent., they appear to be all subjected to the same 

 process in the attempt to extract this ingredient. According to 

 Weber,* the resins can be removed by extracting with acetone in a 

 Soxhlet extractor, the highly porous washed sheets of rubber lend- 

 ing themselves best to this purification process. The complete 

 extraction of these resins from rubber requires many days. The 

 presence of the resinous impurities influences the behaviour of 

 the rubber in practical working and also the stability of the finished 

 article. Owing to the supposed detrimental effect of the resins after 

 vulcanization, no efforts are spared to reduce them to the desired 

 quantity in the inferior brands of rubber. The extraction of some 

 of the resinous bodies from the latex of certain plants is a subject 

 which, though crowded with difficulties, might profitably engage 

 the time of the producer in the Tropics. 



Albuminoids. — The albuminoids, which either alone or with other 

 substances lead to putrefaction, exist almost entirely in solution 

 in the fresh latex. Their removal from commercial rubber on a 

 large scale is considered by many to be almost impossible, and 

 Weber suggested that an expeditious method would be to centri- 

 fugalize the solutions, a method which has been dealt with when 

 describing the machines used in preparing and purifying rubber. 



The addition of formaldehyde to some latices is supposed(l) 

 to prevent the coagulation of the albumen and (2) to cause the 

 indiarubber to collect on the top of the mixture. The proper 

 application of this reagent to Castilloa latex is said to free 

 the rubber from every trace of albuminous matter. It has, 

 however, been questioned whether the caoutchouc would coagulate 

 or even coalesce, if all albuminoids were removed from the latex. 



(5-6) Bulletin of Imperial Institute, Sept. 1904 (Rubber from Burma). 



(7) Technical Reports and Scientific Papers, Imperial Institute, 1903. 



(8) Bulletin of Imperial Institute, Vol. 1, p. 69, 1903. 



* Weber, I.e., p. 3. 



