THE SCIENCE AND PRACTICE OF PARA- 

 RUBBER CULTIVATION 



THE NEW TROPICAL INDUSTRY OF THE EAST 1 



Part II. — Rubber Preparation. 



By JOHN PARKIN, M.A., F.L.S. 



The simplest method of obtaining solid rubber is to allow the 

 latex to dry naturally. There are several objections to this 

 plan. Impurities, such as particles of bark and soil, are apt to 

 be incorporated, lowering considerably the quality of the rubber 

 produced. An undesirable amount of water is also liable to 

 be enclosed in the caoutchouc-mass. Further, if the latex be 

 allowed to dry in the open air, it may become exposed to 

 direct sunlight, and the heat from the sun's rays in the tropics 

 is sufficient to cause permanent stickiness, rendering the rubber 

 of little value. Moreover, many latices, notably those of Hevea 

 and Manihot, putrefy on standing, and an evil-smelling, caout- 

 chouc of inferior grade is the result. Even if the latex be 

 strained to remove foreign particles, and a preservative be 

 added to prevent putrefaction, ordinary drying is a very slow 

 and tedious process, especially as the latex usually requires 

 some dilution to facilitate the straining. Consequently speedier 

 methods of preparation have been devised. These depend 

 for the most part on taking advantage of the phenomenon 

 known as coagulation. But before treating of this important 

 subject, the separation of the rubber by centrifugal force requires 

 consideration. 



Centrifugalisation 



Centrifugal force was first applied to the separation of the 

 caoutchouc globules from the latex by Prof. Biffen. 2 In 1897 



1 Continued from p. 416. As this article is appearing in two parts, it may be 

 well to point out that the first part dealt principally with the Extraction of the 

 Latex from the Para Rubber Tree {Hevea brasiliensis), the chief interest lying in 

 the phenomenon known as wound-response. This, the concluding part, deals 

 mainly with the Preparation of the Rubber from the Latex with coagulation as the 

 central feature. 



2 Biffen, R. H., Annals of Botany, 1898, 12, 165. 



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