August, 1910,] 



105 



Saps and Exudations, 



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 composition and properties of 

 india-rubber. He set to work to investi- 

 gate the matter and found that isoprene 

 could be changed into caoutchouc in 

 two ways : either by very slow poly- 

 merisation in the presence of a trace of 

 acid, such as had occurred in his labor- 

 tory by chance, or by bringing isoprene 

 into contact with strong aqueous or 

 moist gaseous hydrochloric acid. The 

 first method is not a practical one on 

 account of the long period required, and 

 the second could not be made a com- 

 mercial success, as the caoutchouc is 

 merely a small by-product in the for- 

 mation of isoprene hydrochloride ; and 

 further the yield of isoprene from 

 turpentine — the starting point of the 

 synthesis— does not proba bly exceed ten 

 per cent, under favourable conditions. 

 Tilden confesses that after two years' 

 experimentation he had to reluctantly 

 abandon the subject, seeing no way of 

 making synthetic rubber commercially 

 possible. 



Even if future research should result 

 in the production of artificial caoutchouc 

 in quantity, it is very doubtful if it 

 could ultimately compete with natural 

 rubber, especially the plantation 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 synthesised product might cost 

 nearly as much. Then, again, though the 

 artificial rubber might appear, as far as 

 chemical analysis could show, identical 

 with the natural article, it might be 

 lacking in the essential physical pro- 

 perties. The synthesis of a colloid like 

 caoutchouc, presumably of high molecular 

 weight, is a problem of a different order 

 from that of such comparatively simple 

 crystallisable bodies as vanillin or even 

 indigo. 



However, at the present price of 

 rubber, a synthetic commercial rubber of 

 passable physical properties would not 

 only be a boon, but a lucrative discovery. 

 Patents have been taken out, and even 

 companies floated for the production of 

 synthetic rubber, but nothing visible has 

 appeared yet ! 



• It i3 important also here to draw a 

 clear distinction between a true syn- 

 thetic caoutchouc and the so-called 

 artificial rubbers. These latter are 

 merely substitutes or adulterants, and 

 would be discarded if raw rubber were 

 14 



cheaper. They are prepared chiefly 

 from oils, linseed being considered the 

 best. 



It is, of course, not the purpose of this 

 paper, even if the writer had the neces- 

 sary knowledge, to deal with the chemis- 

 try of caoutchouc. This part of the 

 subject has already received full treat- 

 ment in the pages of "Science Progress." 

 Suffice it here to say that through the 

 important researches of Prof, Harries 

 attention is now being directed, towards 

 the synthesis of caoutchouc from car- 

 bohydrates. This investigator has shown 

 good reasons for regarding caoutchouc 

 as related to the pentoses, and so it is 

 suggested that in the plant it may be 

 derived from such sources. 



Concluding Remarks. 



This new industry then appears to 

 have a most hopeful future before it. 

 The time, however, has by no means 

 arrived when managers of estates can 

 content themselves with any rule-of- 

 thumb methods, Eastern planters seem 

 fortunately well alive to this, and now 

 recognise the value of true scientific 

 help. A manager of a well-known estate 

 bas recently put in print some admir- 

 able " Conclusions" on rubber cultivation. 

 One of these reads " That text-books on 

 rubber-planting should only be regarded 

 as historical works" — a maxim, I venture 

 to say, of wider application. 



Everything connected with this novel 

 cultivation is still largely in the experi- 

 mental stage. It is a pleasing sign to see 

 directors of companies deliberating upon 

 the advisability of employing scientific 

 experts on their estates. Considering 

 that such enormous profits are now 

 being made by the- older companies, a 

 small fraction of their receipts might 

 well be spent in this way. Planters 

 should not be content with the scientific 

 assistance rendered by the Government 

 alone. A superintendent of an estate 

 has not the time at his disposal, nor 

 probably the necessary training, for 

 carrying out laboratory experiments, or 

 for keeping a sharp look-out for the 

 initial stages of disease— a vital point. 

 Joint experts for several neighbouring 

 estates might well be employed. Money 

 so spent upon plaut sanitation should be 

 regarded in the light of insurance. 



It is also gratifying to note that this 

 new tropical industry is almost wholly 

 of British origin. The seeds were collect- 

 ed in Brazil and transhipped by an 

 Englishman. Kew raised the young 

 plants and sent them to the Middle East. 

 The Botanic Garden Departments there 

 took charge of the trees and made the 

 first tests upon them, bringing their 



