98 PARA RUBBER. 



to temperatures as high as those to which the superior grades 

 such as "Fine Para" are subjected. When thoroughly dry it 

 is stored, but well protected from light and moisture till required 

 for manufacturing purposes. 



Previous to manufacture the lace-like sheets of rubber are 

 masticated into a homogeneous texture by being passed between 

 large hollow steam-heated rollers. 



Owing to the various defects of raw rubber for industrial 

 purposes, it will be evident that its use would have been con- 

 siderably limited had it not been for the discovery of the various 

 methods of vulcanisation, which consist in causing masticated 

 rubber to be intermixed with various proportions of one of the 

 different forms of sulphur by the action of heat. At normal 

 temperatures sulphur has, however, no visible effect upon rubber. 



PREPARATION OF RUBBER FROM LATEX. 



The preparation of rubber from the latex is one of the most 

 important points which the rubber planter has to consider, as 

 the commercial value of the product will largely depend upon 

 the manner in which this has been carried out. The low price 

 obtained for many grades of rubber is due, in a great measure, 

 to careless preparation. 



The West African rubbers afford striking examples of this 

 kind. They are often contaminated with dirt, stones, bark, &c. ; 

 spurious latices are added to good ones, and the resulting mixture 

 is often a " tacky," putrescent mass, giving out a most offensive 

 odour. 



Quite a few years ago Congo rubbers only realised from is. 

 to is. 6d. per lb., but now that they are more carefully prepared 

 they often fetch 45. per lb. 



The methods in use in different parts of the world for the 

 coagulation of rubber from latex are exceedingly numerous and 

 varied. 



Coagulation may be effected by heating the latex, or by 

 adding either an acid or alkaline solution, while the latex of 

 some trees may be coagulated by simply exposing it to the 

 atmosphere. 



Whichever method be employed, the nitrogenous matter in 

 the latex is coagulated, and the rubber globules are carried down 



