RUBBER PLANTING 159 



these it is allowed to stand for some hours until a firm 

 clot is formed, which can be lifted out in one piece and 

 rolled into sheet. The pans vary in depth from 2 to 

 4 inches, according to the thickness of the sheet required, 

 and a common size is 9 by 18 inches. 



As opposed to coagulation, a centrifugal method of 

 separating the rubber globules from the latex was sug- 

 gested some years ago by Bitten. An electrolytic 

 method of separation has recently been patented by 

 Cockerill. In addition to these methods, various forms 

 of mechanical churns and separators have been recom- 

 mended for use in connection with acid coagulation. 

 The ordinary method has a considerable advantage 

 over all the last-named processes in the matter of 

 simplicity, and it seems likely for the present to hold its 

 ground. The centrifugal method has however a special 

 use in dealing with Castilloa. At present the method of 

 creping is decidedly the most convenient and the most 

 rapid for dealing with large quantities of latex. 



Washing. 



The majority of commercial rubber, as purchased by 

 the manufacturer, contains numerous impurities in 

 various proportions. The first step in dealing with 

 all wild rubbers is therefore to subject them to a 

 thorough process of washing and purification. The 

 following mean values of the loss in weight on 

 washing are given by Weber for different commercial 

 rubbers. 



