88 



26. Before commencing to coagulate, it is essential that the 

 necessaiy heat and smoke has been raised and that the furnace 

 fire is burning briskly. The rate of combustion is then controlled 

 by dampers and the requisite heat can be maintained by a slow fire, 

 which, with a heated furnace, dries up most of the moisture in the 

 fuel while affording sufficient smoke on the belt in its passage over 

 the pipes. The smoke chamber is constructed with a raised or lantern 

 roof providing sufficient ventilation for the air and smoke surcharged 

 with vapour from evaporation of moisture in the latex on the belt, 

 thus excluding condensation within the smoke chamber. (It is best 

 to admit ai^- at the bottom of the chamber too, and blanket the smoke. 

 Free circulation of air allows induced draught and the ready escape 

 of smoke from the supply pipes, such dry filtered smoke is then 

 retained sufficiently long to take up all the moisture 'evaporated 

 during the chamber. When these factors are all in harmony perfect 

 coagulation is assured.) 



27. For the process of coagulation the supply vessel, through 

 which the travelling belt passes, is made shallow and to contain very 

 little latex so as to preclude the possibility of coalescence 

 from a smok}- belt. This supply vessel is supplied from a reservoir 

 at about the same rate that the latex is removed by the belt, and both 

 vessels are specified to be placed outside the smoke chamber in view of 

 preventing coalescence from tlie proximity of smoke. 



28. The belts may be made of canvas, or other similar mattrial, 

 dipped in rubber solution and vulcanized so as to obtain a smooth 

 outside surface, which is necessary for the easy stripping of the belt 

 after coagulating. The length of the belts is estimated at forty-two 

 feet overall, and the width may vary from a few inches to two feet 

 a greater width is considered unwieldy. 



2g. As the belt passes through the supply or feeding vessel a thin 

 layer of latex adheres to the belt in its most expanded form and is 

 then exposed to the action of smoke and this re-agent immediately 

 separates much of the water in the latex on the outside of the belt. 

 The pulleys, too, which support the weight of the belt — if maintained 

 at slight tension, — afford sufficient pressure on the belt to express out 

 most of the remaining water left in the latex on the outside of the belt, 

 from where some drops off as clear water, while the the remaining 

 moisture is evaporated by heat and smoke and the resulting caout- 

 chouc is coagulated into a concentric film of rubber. Smoke is there- 

 fore the host in three different functions of the' process ; (a) it is the 

 host which carries the compound re-agent which separates the water 

 from the caoutchouc in the latex ; (b) it is the host which absorbs and 

 carries off excess moisture within the chamber ; (c) it is the host which 

 fixes the re-agent in the coagulated latex and thus resists oxidization. 

 The process, therefore, consists of coagulation by separation of water 

 from the caoutchouc in the latex by heat and smoke in concentric 

 layers between films of smoke on a travelling belt in which every 



