279 



Saps and Exudations. 



Because the best Para in cur ing is submitted to a heat probably greater than 

 212°, and because, on the best authority, the most of the best Congo is boiled in the 

 curing, I tried boiling the Castilloa latex. The result was not satisfactory. A large 

 proportion of the rubber in the latex coagulated, but there remained always a 

 residuum of milky fluid which no amount of boiling would cause to give up its rubber. 

 The Brazilian method was put aside as too expensive. Blowing smoke through the 

 milk by means of a blacksmith's blower attached to a furnace was tried, without 

 any success. When, however, the latex so smoked was boiled the rubber separated 

 completely, leaving a lye-colored water without a trace of rubber. From these 

 experiments the conclusion was made that smoke and heat would effect coagulation. 

 Having a steam boiler, the apparatus of which I present a rough drawing was set up. 



Bubber Smoking Apparatus. 



| a Steam Boiler ; b Steam Pipe ; c Steam Syphon ; d Discharge Pipe; e Latex Vat ; _/ Smoke 

 Slaking Furnace ] 



Steam passing from the boiler through the siphon continues through the 

 discharge pipe, drawing with it into the latex the whole smoke supply of the fur- 

 nace. The latex is violently agitated and gradually reaches boiling heat. As the 

 boiling point is reached, the rubber completely coagulates. A few minutes of boiling 

 is enough. The coagulated mass is then lifted out and sliced thin and hung over 

 poles to dry. Because of the working of steam in the mass, it is porous and drys 

 very quickly. Indeed, there is no other way of drying rubber except by reducing it 

 to paper-like sheets. 



The process is quick, simple, and cheap. Rubber so coagulated has been kept 

 "six months without sign of viscidity or shortness of grain. The method is in effect 

 that of Brazil, and its chief merit, aside from solving coagulation, is, I venture to 

 think, the diffusion through the rubber of the preservative elements of wood-smoke. 



The active principle of coagulation with heat is doubtless acetic acid. It has 

 been suggested to me by Professor Lang, of Toronto University, that crude wood 

 alcohol, that is alcohol from which the acetic acid had not been removed, might be 

 an effective coagulant. 



It was found that it did not do to use woods for smoke production which 

 blazed readily, and so, I venture, consumed the necessary elements of smoke. At last, 

 it was demonstrated that the best fuel was the nuts of what is locally known as the 

 silico palm, growing very extensively in the swamps of Nicaragua and possibly 

 identical with that producing the rubber curing nuts of Brazil. No doubt, their 

 virtue lies solely in the fact that they give off a dense smoke and simulate a wood 

 distillation. But I bow to the chemists. We use, in bleeding, clay to make a contin- 

 uous surface from the bark into the receiving cups. Some of this clay mingles 

 with the latex and, if not removed by washing, will hinder by its mechanical action 

 the success of the process of coagulation described above.— Gordon Waldron in the 

 India Rubber World. 



