PARA RUBBER. 117 



article, free from mixtures of proteids, resins, &c. Weber strongly- 

 recommended such a process of treating the latex for eliminating 

 proteid constituents. 



Biffen claims that the rubber may thus be prepared by purely 

 physical means ; the light rubber globules are thrown out of the bowl 

 in an almost dry state, and the rubber is free from any obnoxious 

 smell and danger of decomposition. It is, however, questionable 

 whether pure caoutchouc free from resinous and other impurities 

 is desired by the manufacturers. 



Experiments in Ceylon. 



Furthermore, several small experiments carried out in Ceylon 

 have proved that the caoutchouc in ordinary Para latex is not rapidly 

 separated by the centrifugal machine, even when the speed is as high 

 as 11,000 revolutions per minute. In these experiments various 

 heavy chemicals have been added to the latex after the formalin ; 

 the chemicals used do not show an acid reaction, and considerably 

 increase the density of the alkaline mother liquor. The whole 

 of this mixture has been placed in the "Aktiebolaget Separator," 

 and then been subjected to centrifugal force for over an hour, and 

 yet the caoutchouc globules have not been effectively separated 

 from the other constituents. 



Though these experiments cannot at present be considered a suc- 

 cess, the principle of increasing the density of the mother liquor by 

 addition of readily soluble and heavy substances, and then causing 

 a separation of the caoutchouc globules by mechanical means, is one 

 which cannot be too strongly impressed on the experimentalist. 



Rapid Coagulation by Mechanical and other Means. 

 The Michie-Golledge Machine. 

 Construction. —On Plate 21, Series A, a sketch of parts of this 

 machine is shown. The Michie-Golledge Rubber Coagulating 

 Machine consists of a revolving cylinder A, with angular ribs B on its 

 inside, and curved blades C which are fixtures, as shown in the 

 accompanying sketch. The latex is poured into the cylinder A, 

 which is then set in motion, the machine revolving in the direction 

 indicated by the arrow. The revolving cylinder and its ribs B force 

 the latex forward on to the blades C, which carry it into the centre 

 of the cylinder, creating a kind of vortex or whirlpool, and depositing 

 the rubber in the central space in the form of a sponge-like mass 

 shown on Plate 22, Series A. When the mass of rubber reaches the 

 right consistency, it is removed by hand, separated into lumps of 

 the required size, and rolled out while it is still soft into sheets in 

 a small rolling machine. 



Method of Using.— The latex is diluted, often as much as 400 per 

 cent., and after being strained to remove the mechanical impurities 

 and treated with acetic acid in the proportion of 1 dram of acetic 

 to 1 gallon of the diluted latex, is placed in the churn-like cylinder. 



