216 



Iii case the preparation has to be postponed, a small amount of 

 dilute formalin is slowly added from an automatic drip-can. From 

 the collecting tank the latex passes through a strainer into a 

 stirring vat, where more water is added, and the mixture is well 

 stirred ; the temperature being slightly raised with steam passing 

 through pipe coils inside the vat. 



If we adopt a smoking or fumigating process, which is not yet 

 definitely decided, the latex should next pass into a zinc cylinder 

 and through a series of sieves between which the fumes are 

 pressed. The thoroughly fumigated latex falls into a vessel 

 whence it is run off, fifteen minutes later, into settling tanks. 

 Here the creaming of the latex takes place, and by very gentle 

 stirring of the top layer of "cream" coagulation is assisted. 

 Sometimes a coagulant has to be added, but more often the latex 

 shows a tendency to coagulate too rapidly. From time to time 

 some of the mother liquid, which is dark brown, resembling beer, 

 is drawn off from below and clean water is slowly added. 



The coagulated rubber slabs are passed on to the washing 

 machine, and after a thorough washing the rubber is dried in 

 vacuo. 



It is very difficult, even by adding coagulants, to effect the co- 

 agulation of all the rubber in the latex. As an adjunct to the 

 creaming process all of the remaining latex, after two creamings, 

 is passed through a centrifugal separator, and after this the mother 

 liquid does not contain any more rubber. 



All the rubber is pressed into blocks in a strong screw press 

 after drying. Two years ago Mr. HARRISON prepared with 

 tartaric acid on La Zacualpa a big rubber block as an experiment 

 and it proved to be the most attractive and practical way in which 

 we can ship the clean plantation Castillo.. I have received the 

 advice from English rubber brokers to send Cast ilia rubber as 

 crepe, but I greatly doubt the advisability of this, as the oxidation 

 would be considerable, and Castilla suffers more from this than 

 Para rubber. 



SULPHURIZING THE LATEX. 

 The addition of finely pulverized sulphur by a process corres- 

 ponding to the vulcanization suggested itself in the early stages 

 of my experiments with Castilla latex in the laboratory at La 

 Zacualpa. This sulphurizing the latex is, of course, easily feasible, 

 but beyond its preserving action on the crude rubber there is very 

 little to recommend it to the planter. From the manufacturer's 

 point of view, however, a very strong objection will be raised, 

 and it seems to me this cannot be overlooked, In whatever way 

 we add solid sulphur to the latex, the quantity will vary on different 

 plantations and no uniformity can be achieved. 1 his method 

 further lends itself to adulteration, which the rubber buyers always 

 seem to be afraid of. It would in every case be necessary for the 

 manufacturer to analyse his crude rubber for sulphur, and in most 

 instances he would have to desulphurize the rubber before vul- 

 canizing. As the rubber must be masticated before it is mixed 



