174 THE AFRICAN RUBBER TREE 



Coagulation of Fimtiunia Latex. — The coagulation of the 

 latex of Funtumia elastica presents a number of interest- 

 ing featiu-es, the most important of which is that it is 

 much more difficult to induce complete coa,gulation in 

 fresh latex than in that which has been kept for one or 

 more days. In consequence of this fact processes of 

 coagulation which answer weU for old latex are some- 

 times ineffective or onh' partially successful when 

 applied to latex -nliich has just been collected from the 

 trees. 



The methods of coagulation which liave been proposed 

 for use on plantations may be grouped under the following 

 heads : (1) by alloAving the latex to stand until coagula- 

 tion occurs ; (2) by creaming ; (3) by boiling ; and (4) by 

 the addition of coagulants. 



Spontaneous Coagulation. — Attempts have been made 

 to prepare Funtumia rubber in biscuits by allowing the 

 latex to stand in shallow vessels until coagulation has 

 taken place. If glazed vessels are used, however, the 

 process is too slow to be of practical value, as complete 

 coagulation may take as long as three weeks. 



A modification of this method, in which the latex is 

 allowed to stand in shallow trays of soft wood, has been 

 successfully employed in the Cameroons. The wood 

 absorbs the aqueous portion of the latex, and in two or 

 three days a sheet of rubber is left in the tray. 



Creaming. — If Funtumia latex be diluted with five to 

 ten times its volume of water, it " creams " on standing, 

 and a coherent cake of rubber is finally obtained. This 

 method is, however, slow, like that of the spontaneous 

 coagulation of the undiluted latex, and the formation 

 of the cake of rubber may take a week. 



Boiling the Latex. — This method has been adopted in 

 Southern Nigeria for the preparation of rubber from the 

 communal plantations of Funtumia trees, as it is the most 

 suitable for native use. It has been found that the latex 

 does not coagulate quickly unless actually boiled, so that 

 the use of a double pan has been abandoned and the 

 diluted latex is heated directly in the following manner : 



One and a half pints of water are placed in a 3-pint 

 saucepan and raised to the boiling point, when J pint of 

 latex is added. The rubber which separates is kept off 

 the sides of the vessel by stuTing with a stick, and the 



