4 THE RUBBER INDUSTRY 



Tests made with acetic acid show that fifteen to 

 twenty minutes are required before coagulation takes 

 place. 



From the white Hevea the rubber obtained is desig- 

 nated locally as fraca (weak). It is, however, of good 

 quality, and the fraca fina and fine island grades sell 

 readily at only 20 per cent, less value than fine hard 

 Para. It has less resiliency than the product of the 

 black Hevea, and, as a general rule, less care is taken 

 in its manufacture, with the result that the percentage 

 of impurities is greater than is the case with the rubber 

 from the upper rivers. The latex from the Itapiru 

 (Hevea Guayanensis) and the Bariguda (Hevea spru- 

 ceana) is mixed frequently with that from the white 

 Hevea whenever those varieties are plentiful in the 

 neighbourhood. 



The latex of the red Hevea reaches the market in 

 a condition locally qualified as " soft." It does not 

 coagulate as freely as the black and white species, and 

 contains a greater percentage of moisture than the 

 other two varieties when forwarded for shipment, the 

 consequence being a lower selling value. 



Scrap, or sernamby, is an unavoidable by-product, in 

 more or less degree, of all classes of rubber, and it 

 forms a considerable proportion of the total export 

 from the Amazon Valley, often representing 15 per 

 cent, of the annual shipments. In the upper rivers 

 the scrap comprises only the unavoidable cup coagula- 

 tions and the lump formed when the latex is being 

 brought in to the smoking-house ; but in many dis- 

 tricts of the Lower Amazon the latex is allowed to 

 remain purposely in the cups until coagulation has 



