608 SCIENCE PROGRESS 



at the moment of rupture gave results equal, if not superior, 

 to those of fine Para. They consider therefore that the state- 

 ment that plantation rubber is wanting in " nerve " is not 

 justified, and conclude that the new product will turn out to 

 be at least as good as, if not superior to, Brazilian fine Para. 

 The variation in the quality of plantation rubber which is to 

 be observed at times should be attributed rather to differences 

 in the method of treating the latex than to the age of the trees. 



Brief reference has already been made to Spence's work 1 on 

 the protein in rubber. By using suitable staining reagents he 

 was enabled to demonstrate a fibrous reticular structure in raw 

 Para rubber, due to the distribution of " cured " protein 

 throughout the mass. He considers that it most likely plays 

 an important part in the quality of the rubber, adding notably 

 to its strength, and thus is a desirable adjunct. To militate 

 somewhat against this view is the fact that in the processes 

 of mastication and vulcanisation such structure must most 

 likely disappear. However, as raw rubber is sold on its 

 strength, whatever may add to this deserves consideration. 

 Protein in the uncured state is no doubt a disadvantage at 

 times, because such rubber, if kept damp, will mould and 

 deteriorate. Even if protein be undesirable or inert, it does 

 not seem to be practicable at the present time to prepare raw 

 Para rubber without it. Hevea latex will not submit to 

 separation by centrifugal force, otherwise a caoutchouc free from 

 protein could be readily prepared. All methods of coagulation 

 must result in the incorporation of albuminous matter in the 

 rubber mass. Perhaps, by means of filtration or by the electrical 

 method of separation, caoutchouc free from protein might be 

 prepared on a laboratory scale and then compared with the 

 article obtained by coagulation. 



Further, the question arises are all caoutchoucs when pure, 

 i.e. free from resin, protein, etc., identical in physical properties? 

 Is, for example, that of Castilloa, Manihot, or Ficus equal in 

 every way to that of Hevea ? They possibly are, but there 

 seems a probability that they are not. In Hevea it has been 

 fairly well proved by Bamber that the rubber from four-year-old 

 trees, though inferior to that from older trees, has the same 

 chemical composition ; and further the product from two-year 

 stems, though sticky and without strength, showed little 

 1 Spence, Quart. Journ. Liverpool Inst. Com. Research, 1908, 3, 58. 



