72 CENTRAL AMERICAN RUBBER TREE. 



required. It is the albuminous substances incorporated in Castilla 

 rubber which continue to ferment and putrefy, or otherwise contribute 

 to the deterioration of the rubber, both crude and manufactured. In 

 other words, it is the albumens rather than the resins which determine 

 the inferiority of rubber, and the amount of resin contained in the 

 latex of adult Castilla trees is held to be "entirely innocuous" and 

 "absolutely unobjectionable." Dr. Weber continues: 



I am quite aware that now and then all sorts of sinister actions are ascribed to the 

 presence of resins in india rubber, but there is not the least particle of evidence to 

 show that they are intrinsically detrimental. As a matter of fact, in the manufac- 

 ture of quite a number of rubber goods, resins are deliberately added to the mixings. 05 



OTHER METHODS OF COAGULATION. 



The traditional method of treating Para rubber in Brazil is to spread 

 it in thin layers on wooden paddles, which are held over burning- palm 

 nuts. The highest grades of commercial rubber have been produced 

 in this way, but the process is too slow, laborious, and disagreeable. 

 There seems, however, to be ground for a suspicion that some constit 

 uent of the smoke, which is incorporated into the rubber, may have a 

 beneficial effect upon its mechanical properties, and the previously 

 cited adverse opinion upon the pure but unsmoked Hevea rubber from 

 the East Indies seems to give further warrant for such a notion. The 

 experiment of smoking Castilla rubber has been tried at La Zacualpa, 

 but the result was a hopelessly sticky mass. The difference of behavior 

 is, however, more likely to be due to differences in the latex rather 

 than to differences in the rubber itself. 



It is not to be overlooked that, while the high percentage of albu- 

 minous impurities in Castilla rubber has rendered the price lower and 

 the removal of them should increase the price, yet it will reduce the 

 quantity of the marketable product and will thus not be an unmixed 

 advantage. All the methods of coagulation now in use bring about 

 the incorporation with the rubber of a large amount of the albuminous 

 substances of the latex. Dr. Weber claims that if none of the albu- 

 mens are left out the}- will constitute over 25 per cent of the solid 

 product and adds: 



The native rubber collectors prepare the rubber from the latex in such a way that 

 at least part of the aqueous vehicle of the latex is drained away before coagulation 

 takes place, and consequently we never find a Central American rubber (crude) 

 which contains as much as the above-stated quantity (25 per cent of albuminous 

 matter), but lots containing from 9 to 13 per cent are quite common.'' 



The meaning of this sentence is not obvious, and it becomes still less 

 so if we read it in connection with one which follows a little later. 



Therefore, whenever we coagulate the rubber, we can only do so by coagulating 

 it in conjunction with the albumen present, and we have at once a product possess- 

 ing all the irremediable drawbacks which above we discussed at some length. 



a Tropical Agriculturist, 22:444, January. 1903. 

 ''Tropical Agriculturist, 22:442. January, 1903. 



