124 THE PARA RUBBER TREE 



of drip-tins is employed to facilitate its flow and thus 

 prevent its coagulation on the stem. The drip-tins are 

 fixed at the upper ends of the incisions and provide a 

 very slow cmTent of water along the cuts. 



If it is desired to keep Pcira latex liquid for any length 

 of time, it should be rendered alkaline with ammonia, 

 or a little formalin should be added. 



When the flow of latex has ceased, the contents of the 

 collecting-cups are emptied into enamelled iron pails and 

 the latex is at once transported to the factory. 



Preparation of the Rubber. — ^On arrival at the factory 

 the latex is first strained in order to remove all mechanical 

 impurities, either by passing it through sieves of wire 

 gauze or coarse cloth, or by means of centrifugal strainers. 

 Sometimes the straining is done at the tune of collecting 

 the latex from the cups, the pails being fitted with a sieve 

 for the purpose. 



The method most generally adopted on the plantations 

 for coagulating Hevea latex is to render it faintly acid by 

 the addition of acetic acid. The use of a large excess of 

 acid is undesirable and should be avoided. Several 

 other acids, e.g. formic acid, lactic acid, and hydrofluoric 

 acid (purub), and other coagulants are also employed to 

 prepare Para rubber, but none of these is so extensively 

 used as acetic acid. 



When the rubber is prepared in the form of biscuit 

 or sheet without the use of machinery, the acidified latex 

 is simply allowed to stand in circular or rectangular 

 vessels until coagulation has occurred, and the cakes of 

 rubber obtained are washed, pressed, and dried. 



If, however, large quantities of rubber are being dealt 

 with by machinery the latex is usually coagulated in 

 bulk in large tanks, the necessary amount of acetic acid 

 being stirred in and the liquid allowed to stand until 

 coagulation is complete. Sometimes the coagulation of 

 the latex is accelerated by churning it, after the addition 

 of acetic acid, in machines such as the Michie-Golledge 

 Coagulator or the K.L. Coagulator. Tlie freshly coagu- 

 lated rubber obtained by these methods is then rolled 

 out into sheet or crepe by the machines. 



The chief forms in which plantation Para rubber 

 appears on the market are (1) biscuits, (2) sheet (smoked 

 iind unsniokcd), (3) crepe, (4) block, and (5) scrap. 



