Gums, Resins, 



198 



[April 1907. 



water and a small amount of vegetable matter. After purification, however, the 

 amount of caoutchouc is much higher, and Markwald and Frank found 77 per cent- 

 in a sample which they examined. Formerly the rubber was only worth Is. 4d. 

 per lb., whereas the improved product can be sold at 2s. 4d per lb., or more. It is 

 stated that a small quantity of rubber extracted from the dried plants in Germany 

 by a laboratory process was valued in that country and in England at from 3s. 2d. 

 to 3s. 8d. per lb. 



It appears certain, therefore, that the Guayule plant will furnish rubber of 

 very fair quality, but it remains to be seen whether the extraction of this rubber 

 upon a commercial scale will prove successful. The plant can be cultivated in 

 sterile regions unsuitable for other purposes, and as it can be collected all the year 

 round, the industry will be continuous. On the other hand, there will be certain 

 difficulties in working on a large scale, as the places at which factories can be 

 established are limited owing to the necessity of having a liberal supply of water, 

 and in some cases the plants may have to be transported some considerable distance 

 before treatment, thereby increasing the cost of production. These points will be 

 cleared up, however, by the experiments now in progress, which will demonstrate 

 the possibility or otherwise of successfully utilising the Guayule plant as a source 

 of rubber. — Bulletin of the Imperial Institute. 



RESIN IN RUBBER. 

 The plantation rubber cured by the process described by me in a recent 

 number of the India Rubber World (March 1, 1900, page 188) was found by the 

 factory, which purchased it, to contaiu a large percentage of resinous matter, though 

 not as much as rubber cured on a neighbouring plantation from trees of the same 

 age by evaporation or absorption only. 



Further study leads me to believe that planters have been misled by the 

 demand of manufacturers for a perfectly dry rubber. To dry perfectly, one must 

 make rubber into very thin sheets, pancakes, or crepe. Complaint is made of all 

 these, whether they be of Caslilloa or Para, and the reason would seem to be resin. 

 Whence the resin? That is a question I wish manufacturers and planters would set 

 themselves to answer at once. It will take the planter alone years to answer, 

 because he is not a chemist. If the manufactiu'er will help, it will take 

 weeks only. 



I submit for consideration my view, based on a planter's observation. Resin 

 or the most of it seems to be due to drying and exposure. Caslilloa, the core of a 

 ball of the finest Para, and the best Congo, cut thin and thrown into a drawer for 

 a few months, became almost equally gummy and pasty, a state which I assume 

 to indicate resin. Castilloa, if kept long enough, will run down from the shelf, 

 here, like tar. The white core (that is to say, the part not completely dried) of a 

 thick piece of plantation Castilloa answers all the visual and actual tests of the 

 best Para, while the dry skin is short and tacky, the more the older. What takes 

 place? Is it due to oxygen, light, or bacteria? Will some one make tests of the 

 white hermetically sealed core and the black rim of a ball of Para, of white 

 plantation Castilloa, and thin, sticky pancakes or sheets of the same of crepe, 

 of rubber milk, etc. ? If the resin does not come out of the tree, the planter will 

 know what to do and the manufacturer will doubtless reform his method of 

 drying by exposing for weeks or months thin sheets of mangled rubber, 



R. World, GORDON WALDRON. 



Nicaragua. 



