151 



■of smoking. On examination in the usual manner, it was found that 

 the rubber contained a very high percentage of " resin" (i.e., matter 

 soluble in acetone), amounting to 5.2 per ce«t on the dry material. 

 This proportion of resin is very much higher than is usually present 

 in Para rubber from the East, but owing to the smallness of the 

 samples supplied to the Imperial Institute it was not possible to 

 investigate the matter in detail. Subsequently, however, a large speci- 

 men of smoked rubber, carefully prepared from the latex of a single 

 tree by the same process as that employed for the earlier specimens, 

 was forwarded for further examination to the Imperial Institute by 

 the Director of the Botanic Gardens at Singapore. 



The specimen consisted of a spindle-shaped piece of smoked 

 rubber, weighing 6 lbs., which was almost black externally but whitish 

 within when cut. The rubber was rather moist, and a quantity of 

 brown viscous liquid was present between the concentric layers. 



An analysis of the rubber gave the following results: — 



Moisture 

 (Caoutchouc ... 

 • " Resin " 

 Proteid 

 Ash 



The percentage of "resin " present in the dry rubber was a little 

 lower than that found in the previous samples ^4.8 per cent, compared 

 with 5.2 per cent.), but was still very much higher than the amount 

 usually present in plantation rubber from the East. 



An examination was made of the portion of the rubber dissolved 

 by hot acetone, and it was found that a large quantity of a solid cry- 

 stalline substance, which was soluble in hot water, was included with 

 the resin. The substance amounted to no less than 2.7 per cent, of 

 the dry rubber, so that the true figure for the percentage of resin in 

 dry rubber was only 2.1 per cent, instead of 4.8 per cent. 



The crystalline substance was submitted to a detailed examina- 

 tion and proved to be a carbohydrate, which was identified-as laevo- 

 methylinosite. The presence of this substance in the aqueous portion 

 of the latex of Hevea brasiliensis remainimi after the coagulation of 

 the rubber has been previously recorded by de Jong, and closely allied 

 carbohydrates are known to occur in other Jatices. The presence of 

 such a large amount ui the /-methylinosite in this specimen of Para 

 rubber is no doubt to be attributed to the method of preparation 

 employed, whereby the whole of the solid constituents of the latex 

 remain in the rubber, whereas in the usual method of coagulation 

 adopted in the East, the rubber separates from the aqueous portion of 

 the latex, which retains the soluble constituents in solution. 



