and Magazine of the Ceylon Agricultural Society.— June, 1910. 563 



and " tacky " rubber from the East has reached 

 Mincing Lane from time to time, and this 

 must tend to damage the reputation of plan- 

 tation Para as a whole. It may be claimed, 

 however, that previous to the arrival of cul- 

 tivated Hevea rubber from the East, no raw 

 caoutchouc so free from impurity and moisture 

 and so pale in colour had ever been put on the 

 market. 



The youthfulness of the trees from which the 

 majority of plantation rubber is at present 

 obtained had been blamed for this supposed 

 lack of strength, The tapping of cultivated 

 Heveas is begun when their stems, at a height 

 of 3 feet from the ground, have attained a 

 girth of about 20 inches. They reach this size 

 under favourable conditions of growth in five 

 or six years from the time of planting. The 

 rubber in the forests of the Amazon is col- 

 lected from much older trees. Then it is an 

 undoubted fact that rubber from quite young 

 trees or twigs of Hevea is very deficient in elasti- 

 city. There has consequently been much opinion 

 expressed to the effect that the latex takes 

 some time to mature and so naturally it is argued 

 that the rubber from old trees must be better 

 than from young ones. But the botanical fact 

 is lost sight of that new laticiferous elements are 

 continually being added by the cambium to the 

 bast, no matter what age the tree may be. These 

 must take time to mature. Previous to their full 

 development they are not likely to yield an ap- 

 preciable quantity of latex. Hence, unless the 

 latex alters its character as the tree grows older, 

 there is no reason for thinking it is less mature 

 in a six or ten year-old tree than in a 15 or 20 

 year-old one ; both will have immature latici- 

 ferous tubes as well as fully functional ones. 



The reason why the latex from young stems 

 and shoots yields an inferior rubber may be asso- 

 ciated with the fact that this latex is contained 

 chiefly in the tubes formed in primary growth. 

 These may quite well differ in the contents from 

 those produced in the so-called secondary 

 growth, which is due to the activity of the cam- 

 bium and by which the tree increases its girth. 

 If there be any truth in this supposition, then 

 this will account for the fact that the rubber 

 from Hevea trees under four years old, and es- 

 pecially of Castilloasof a similar age, is midway 

 in strength between that from the shoots and that 

 from older trees- In such young trees the primary 

 laticiferous tubes will still be yielding some 

 latex, which will mingle with that from the se- 

 condary tubes, giving an intermediate product. 

 Later the primary ones will become wholly 

 compressed by the growth in thickness, and 

 cease to give any latex. 



Further, direct testing of the rubber seems 

 now to be dispelling this notion of an inferiority 

 in the caoutchouc from six to ten-year-old trees, 

 as compared with that from older ones. Beadle 

 and Stevens (Beadle and Stevens, Chem. News, 

 1907, 96, 37, 187) have carried out interesting 

 vulcanisation tests with plantation rubber and 

 fine Para. They argue rightly that, as almost 

 all rubber is vulcanised before use, the trials of 

 comparison should be made after, and not be- 

 fore, vulcanisation. Their results are distinctly 

 favourable to plantation rubber. Testa for 



tensile strength and elongation at the moment 

 of rupture gave results equal, if not superior, 

 to those of fine Para. They consider therefore 

 that the statement that plantation rubber is 

 wanting in "nerve" is not justified, and con- 

 clude 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. 



Synthetic Rubber. 



The possibility of the production of a com- 

 mercial synthetic caoutchouc to compete with 

 the natural article has at times perturbed the 

 rubber-planter, A few years ago the forth- 

 coming of an artificially prepared product 

 looked more hopeful than it does now, In the 

 first place a distinction must be drawn between 

 a laboratory prepared and a commercial syn- 

 thetic rubber. The former has been an accom- 

 plished fact. Bouchardat as far back as 1878 bad 

 noticed that a tough elastic solid, resembling 

 India-rubber was produced by the action of 

 strong acids on isoprene for a number of years, 

 and credit is due to Prof. Tilden for his work in 

 this direction ; no one since apparently has ad- 

 vanced further than he did. A synthesis of cao- 

 utchouc occurred in his laboratory by accident. 

 Engaged at one time in researches on the 

 terpene series of hydrocarbons, he noticed that 

 some liquid isoprene which had been laid 

 aside in bottles for several years had formed 

 clots of solid substance which had the com- 

 position and properties of india-rubber. Ha 

 set to work to investigate the matter and 

 found that isoprene could be changed into 

 caoutchouc in two ways : either by very slow 

 polymerisation in the presence of a trace of 

 acid, such as had occurred in his laboratory 

 by chance, or by bringing isoprene into con- 

 tact with strong aqueous or moist gaseous 

 hydrochyloric acid. The first method is not a 

 practical one on account of the long period re- 

 quired, and the second could not be made a 

 commercial success, as the caoutchouc is merely 

 a small by-product in the formation of isoprene 

 hydrochloride ; and further the yield of* iso- 

 prene from the turpentine— the starting point of 

 the synthesis— does not probably exceed 10 per 

 cent under favourable conditions. Tilden con- 

 fesses that after two years' experimentation he 

 had to reluctantly abandon the subject, seeing 

 no way of making synthetical rubber commer- 

 cially possible. 



Even if future research should result in the 

 production of artificial caoutchouc in quantity, 

 it is very doubtful if it could ultimately com- 

 pete with natural rubber, especially the plan- 

 tation variety, as this most likely could be sold 

 with a fair profit at a price of 3s or even 2s 6d 

 per lb. The raw material required for the syn- 

 thesised product might cost nearly as much. 

 Then again, though the artificial rubber might 

 appear, as far as chemical analysiscould show, 

 identical with the natural article, it might be 

 lacking in the essential physical properties. The 

 synthesis of a colloid like caoutchouc, presum- 

 ably of high molecular weight, is a problem of a. 



