86 



The following criticism of th\< ' creaming" process is given in " Le 

 Caoutchouc et la Gutta Percha": — 4i Ce mode de preparation est bien 

 rudimentaire et ne peat fournir qu'un produit de qualite inferieure, qui 

 perd souvent plus de 50 per cent, surtout lorsqu'il fraichement 

 prepare." t 



Recently there has been some talk of extracting rubber from leaves 

 and twigs by means of solvents, as has been done in the case of gutta- 

 percha. A description of this latter process may therefore be of inter- 

 est. It originated in the smallness of the yield of the Isonandra gutta 

 trees, a tree from 25 to 30 years old, only giving 1*3 lbs of gutta 

 percha when felled. The explanation of this fact is to be found in the 

 work of De Bary, % who showed that the laticiferous system of the 

 tree, consisted of short, closed sacs. This the being the case, a great 

 many would remain unopened, and thus a considerable per-centage of 

 the gutta-percha would remain in the bark. As the demand for gutta- 

 percha has been large, and the supply has been obtained by felling the 

 trees, they have become almost extinct. § 



Serullas proposes to utilise the leaves and twigs of the shoots from 

 the old butts to extract the gum from. They are dried, treated with 

 caustic potash to destroy colouring matters, and treated with solvent for 

 gutta-percha. The solvent is then distilled off and may be used again 

 and again. 



Rather more than lib. of gutta-percha is said to be yielded by 30 

 lbs. of chopped up fresh leaves and twigs. || 



For several reasons 1 do not think this process could profitably be 

 applied to the preparation of rubber. The most important of these are 

 (1) on gathering the leaves and twigs there would bean immense loss 

 of latex, and (2) stripping trees of their foliage (the part which builds up 

 their food supply) invariably kills them. 



The direction in which research work should tend, I venture to 

 think, is to prepare rubber free from the other constituents of latex, so 

 that among other things, freight and customs charges on these impuri- 

 ties may be avoided. 



Now it has been s^hown conclusively that the chemical constitution 

 of latex varies with its source, so that it is improbable that any one re- 

 agent can be found capable of coagulating any given latex. Thus from 

 the fact that acetic acid coagulates the latex of certain Hevea species, it 

 cannot be argued that it will coagulate the latex of a Kicksia species. 



Then expert opinions, as we have seen, show that the preparation of 

 rubber by these chemical means is not satisfactory, for th^ jproduct is 

 far from pure. 



f "Le Caoutchouc." &c, p. 62. 

 X " Comp. Anat- Phan. and Ferns," p. 151. 

 * Serullas." " Kew Bulletin," 1891, ccxiii., 230 g 

 i| * Kew Bulletin," 1891 ccxiv.. p. 231. 



