June, 1910.1 



483 



Saps and Exudationsi 



can be made at a profit. The possibility 

 of rubber rising to this value it considers 

 is very remote, since the output from 

 plantations will increase rapdily in the 

 next few years, so that there is likely to 

 be a decline rather than a further rise in 

 price. The view taken iu the article 

 referred to seems to be that generally 

 accepted by rubber planters, and it must 

 be admitted that at the present moment 

 the chances for the prosecution of syn- 

 thetic rubber seem to be poor. It is gen- 

 erally believedthat in the most favourab- 

 ly situated and best managed plantations 

 in Ceylon the cost of production of sheet 

 Para rubber of the best quality is about 

 Is. 2d. to Is. 3d. per lb., and that such 

 rubber could be marketed profitably 

 at Is. 6d. On the other hand, it seems to 

 be thought that the only possible raw 

 material for the manufacture of rubber 

 is turpentine oil, and with the produc- 

 tion of this article already unable to 

 overtake the demand, it is not a promis- 

 ing source, and its price even now pre- 

 cludes its use f n- rubber manufacture, 

 even if a good process were discovered. 

 It is a mistake, however, to suppose that 

 there are no other promising raw mate- 

 rials. What is needed is a cheap un- 

 saturated hydrocarbon, capable of ready 

 condensation to form very complex mo- 

 lecules, or an unsaturated acid obtain- 

 able in large quantities from which such 

 a hydrocarbon can be easily prepared. 

 Two raw materials naturally suggest 

 themselves in this connection, viz., acety- 

 lene, and one or other of the liquid 

 unsaturated acids of the drying and 

 semi-drying oils, and it is probably by 

 the use of such products that the 

 problem will be solved, if it is solved at 

 all. 



SUBSTITUTES FOR RUBBER. 



By C. Simmonds. 



(Prom Nature, Vol. LXXXIII., No. 2107, 

 March 17, 1910). 



The present demand for india-rubber 

 naturally directs attention to those 

 articles which, to a greater or less degree, 

 may serve to replace rubber in its in- 

 dustrial applications, and so help in 

 conserving the supply. 



Of such articles a very large number 

 have been proposed. Those in actual use 

 to any considerable extent are, however, 

 relatively few. For present purposes the 

 various surrogates may be distinguished 

 as (1; rubber-substitutes proper, consist- 

 ing wholly of ingredients other than 

 rubber; (2) composite or "artificial" 

 rubbers, which contain a certain pro- 

 portion of natural rubber worked up 



with other substances ; and (3) true 

 synthetic rubber, namely, a product con- 

 taining the rubber molecule synthesised 

 in the laboratory or factory by chemical 

 means from simpler compounds. 



At present the first of these classes 

 is commercially the most important. 

 Scores of recipes are in existence, in- 

 cluding very diverse ingredieuts ; but 

 the basis of most is a modified oil. At 

 first sight there seems little sugges- 

 tion of india-rubber in the properties of 

 an ordinary vegetable oil, but a simple 

 experiment will indicate the kind of 

 modification which certain oils readily 

 undergo, and which help to fit them for 

 use as rubber substitutes. If we test 

 the drying properties of boiled linseed 

 oil by spreading a little of it over a slip 

 of glass and allowing it to dry, a film of 

 oxidised oil is eventually obtained, 

 having a certain modicum of toughness 

 of elasticity. The liquid oil has taken 

 up oxygen, and thereby become con- 

 verted into a more or less elastic solid, 

 Tung-oil substitute is essentially such 

 an oxidised product, manufactured by 

 heating the raw oil until it has absorbed 

 enough oxygen to cause it to thicken 

 and become solid on cooling, when it is 

 powdered and worked up with a little 

 petroleum. 



In a somewhat similar way the oils 

 can be made to take up sulphur, be- 

 coming thereby solid and endowed in 

 some degree with elastic properties. 

 The treatment is analogous to the 

 "vulcanisation" of rubber. ''Brown" 

 or "■ black " substitutes are manufactured 

 by beating the oil with sulphur, a pro- 

 cess corresponding to the "hot cure" 

 method of vulcanisation. "White" sub- 

 stitutes may be made by merely mixing 

 the oil, cold, with 20 to 40 per cent, of 

 sulphur chloride ; or, better, by first 

 dissolving the oil in a suitable solvent 

 such as carbon tetrachloride, This 

 resembles the " cold cure "process used 

 iu vulcanising rubber. Colza oil is largely 

 used for these purposes, but various 

 others are available— linseed, maize, 

 arachis, and castor oils, for example. 

 The chemical reaction involved is a some- 

 what complicated one, but probably it 

 consists mainly in the formation of 

 what chemists term an " addition-pro- 

 duct." The proportion of sulphur taken 

 up by the substitutes varies rather 

 widely, ranging from 5 to upwards of 

 15 percent. As would be expected, oils 

 which have previously been oxidised to 

 a notable extent (e.g., "blown" oils) 

 require less sulphur to saturate them 

 than do the natural oils. 



" Nitrated " oils are also used as the 

 basis of some rubber surrogates, Thug 



