212 



" My suspicion was confirmed when treating the latex by a mixed 

 process of skimming and spontaneous desiccation. 



"By this method I obtained a much higher percentage of 

 rubber and only a small residue, consisting likewise of a yellow 

 and viscous matter. However, the rubber was less elastic than that 

 obtained by coagulation in the hot bath. This is not surprising, 

 seeing that the rubber prepared by the latter process contains all 

 the components of the latex and the root sap (excepting the 

 greater part of the water), and, besides, I had not been able to 

 strain the liquid, having no metal net nor adequate strainer 

 with me. 



Processes employed 



Percentage of raw rubber 



per cent. 



• • • 



Coagulation over fire 



„ a in the hot bath 

 Skimming and spontaneous desiccation 



• • • 



"In order to determine the percentage of 

 obtained by these processes, I analysed the samples of 



pure caoutchouc 



" 'Ecanda 1 



rubber prepared in Bengnela, in the chemical laboratory of the 

 Instituto de Agronomia e Veterinaria, with the following 



results : 



Rubber obtained by Coagulation in the Hot Bath 



Caoutchouc 



Resins ' m% 



Substances soluble in water 



• • « 



• • % 



99 



w 



5* 



in alcohol at boiling point 



... ••• •»• 



Impurities not determined 



• • • 



» » 



• • 



• • • 



88*025 per cent. 



4-725 

 1-100 

 1-300 



1-082 



3-768 



»> 



»» 





Rubber obtained by Skimming and Spontaneous 



Caoutchouc 



-m • • ■ • » 



Resins 



Substances soluble in water 



Desiccation. 



• • • 



« • • 



• • • 



♦ • • 



» • • 



• • • 



t* 



Watei 



99 



in alcohol at boiling point 



• • • 



Impurities 



• • % 



* • • 



• * * 



• • 



71-925 per cent. 



3-300 



2-950 



1-385 



3-154 

 16-926 





•I poured the 



linnS nwSi J e I? bber *& tbis method * Proceeded as follows :-I poi 



S?S £ \ 7 the crushing of the ' Ecanda ' roots into enamelled iron dishes 



2rwT^ - aye -V ° m - ^ hick " Aft6r a wh « e ia every one of the dishes and 

 Thfo?k& , J lde8 , a skin of rubber for ™ed on the surface of the liquid, 

 mentiri ^I^^L 8 ? I *?* °* *« two days-the duration of the f P« rl ; 



ment— m.«- .w 1 ' T- • wem ' on tor tw0 days— the duration ot tne «i»"" 



SuTtiono? vL C ° nhn 5 in& x> to form ' b »t ever y time l«w thick. Then. the 



moutchouo nS- ^. ? nt t0 make 8Ure * be ther the liquid still contained 

 caoutchouc I left it m the dishes until the evaporation was complete, which was 



ays after the commencement of the experiment. As thedishes were 

 cne air and the latex somewW. wn^t t>,« c,r. T hflieve that the 



caoutchouc I 

 the case 



j~»»v.t» aw. 



resinified rubber. 



viscous residue which formed consisted 



