479 



vised than the ordinary carpenter's chisel, carefully used with a 

 light mallet. The cuts (three oblique cuts one above another, 

 should be clean cut, and should not penetrate into the wood of the 

 tree. Caution should be exercised in this respect, as if the wood 

 is injured certain species of boring beetles attack the tree. The 

 spacing should be about a span apart, one circle round the trunk of 

 the tree beginning at the ground surface for each day's tapping, 

 and so giving an increased number of cups in use as the tree grows 

 in circumference, with proportionate increase in yield of the latex. 



One advantage of the close system of cultivation recommended, 

 besides greater economy in working is that centrally placed curing 

 stations can be secured. This is necessary in order that the latex 

 may be quickly treated, so soon as it is taken from the trees or 

 much of it will become coagulated before it could be subjected to 

 the smoke-curing process, and so lose the higher market value. 



The Hevea is naturally a large tree, under favourable conditions 

 attaining a girth of 12 ft. in the bole. To stint it in matter of root 

 space or scope will be found to be faise economy. I would, there- 

 fore, strongly deprecate closer planting than that recommended, viz. 

 half chain (33 ft. by 33 ft.), 40 to the acre. Planted and cultivated 

 at this distance and giving say, 5 lbs. of rubber per tree at 2 s - on b f 

 per pound, it would yield at the rate of some £30 per acre for sale 

 of rubber alone, apart from value of the seed crop, to be converted 

 into oil worth ,£25 to £30 per ton. 



The Contract Journal, January 8th, 1902. 



METHOD OF EXTRACTING RUBBER FROM 

 THE BARK OF RUBBER VINES. 



A series of buildings for exploiting the bark of the wild rubber 

 vines in Cochin China are being built. A factory containing 

 machinery for treating 2 to 3 thousand kilogrammes of bark a day 

 is in course of construction at Cho Quan (province of Cholon). I he 

 barks employed are those of Day-Che and Day Nam do trong. 

 The method of treatment will consist in putting the dry bark of the 

 vines to macerate for 4 or 5 days in sulphuric acid at 50 degrees, 

 the cellulose is then destroyed and carbonized, when the rubber 

 remains unhurt by the acid, when taken out of the acid bath, the 

 bark is washed to free the rubber from the acid and especially to 

 recover the acid, which is eventually obtained by evaporating the 

 water in which it has been washed. The disintegrated bark is 

 then put under the action of a separator which can be moved 

 either by hand power or machinery. It receives meanwhile 

 currents of water alternately hot and cold and by this action 

 the bark already dissolved by the acid goes off in a state of mud, 

 the rubber separated collects in sheets about a centimetre in 

 thickness. This operation is rapid enough and scarcely demands 

 more than hand labour, since on 100 Kilogrammes of bark the acid 

 required for the solution 100 Kilogrammes reduced it is since from 

 50 to 45 degrees only entails a loss of 2 Kilogrammes. The rubber 



