213 



;; 



Thus 1 obtained by coagulation in the hot bath 2*125 per cent 



om 



fresh root, and by the mixed method of skimming and spontaneous 

 desiccation 4*574 per cent, of pure caoutchouc ; that is, I obtained 

 by the latter process more than twice the quantity of pure 

 caoutchouc than by the first. 



" It follows, therefore, that, of the processes which I tried, it 

 was the process of skimming and spontaneous desiccation by 

 which I obtained the best result- The great drawbacks inherent 

 in that method are, however, aggravated when it is applied to 

 the treatment of a liquid resulting from the crushing of the 

 Ecanda root, and that makes it hardly practicable. 



" Indeed, as in this case a much diluted latex has to be dealt 

 with, its coagulation (I) requires, ipso facto^ much time ; (2) 

 implies the use of a great number of recipient vessels ; and (3) 

 necessitates a very spacious installation- Moreover, as the latex is 

 not pure, but a mixture of latex and sap, (4) the rubber turns out 

 very impure, the normal constituents of the latex being precipi- 

 tated together with the substances which were dissolved in the 

 sap of the ' Ecanda • root, 



44 No doubt points 1-3 could be improved upon by using for 

 skimming and evaporating very porous earthen pans and keeping 

 the liquid at a relatively high temperature ; but the disadvantage 

 mentioned under (4) is fundamental . . . Possibly better 

 results will be obtained with chemical coagulents with or without 

 the aid of heating . . . But in my opinion the really practical 

 method of preparing the ' Ecanda ' rubber should consist in the 

 centrifugalisation of the liquid obtained by the crushing of the 

 roots. As there was no centrifugal machinery in Benguela I was, 

 to my great regret, unable to try that process." 



4 



Ides' experiments wit! 

 (inhabitants of Bihe) 

 d some of it was actu 



market. Prof. Geraldes describes two of their methods and gives 



them 



method 



and then expose them on the soil to the action of the sun. In 

 this way the exuding latex is converted into rubber by desiccation 

 and partly also by absorption of its serum through the soil. They 

 thus obtain pieces of a mixture of rubber and soil out of which 

 small cylinders (mutares) about 12 cm. by 1*5 cm. are made, or 

 small balls which they join in clusters of 4 or 5, and those 

 clusters are also called mutares (as it were fingers). The mutares 



external 



great 



greatly depreciating the quality of the rubber, has the incon- 

 venience of making them excessively heavy. 



" I analysed several samples of mutares prepared by this method 

 which I brought from Benguela to the Institute. 



Average Composition 



per cent. 



• •• •■» ««« ••♦ ••« *x*7 OJL 



1-50 



Caoutchouc 



XYtcslIlD ••• ♦•♦ ••• ••• • •• ••• 



Substances soluble in boiling alcohol ... 1*27 



Substances soluble in water and impurities •.. 51 a 42 



