October 1, 1912.] 



THE INDIA RUBBER WORLD 



11 



Synthetic Rubber in Germany. 



IN tlie early part of this summer, the question of synthetic 

 rul)ber was dealt with at the Freiburg Congress of the Asso- 

 ciation of German Chemists, by two of the most noted au- 

 thorities on the subject. Dr. Carl Harries, of Kiel, and Dr. Fritz 

 Hofmann. of Elberfeld, respectively treated the matter from a 

 scientitic and a technical standpoint. 



Dr. Harries, in amplification of his previous utterances on the 

 subject at Dantzig, recalled the fact that the basic material for 

 the production of synthetic rubber is isoprene. a relatively simple 

 carbo-hydrate, belonging to the butadeine order, and which has 

 been obtained from the dipentene in turpentine. He regarded 

 the problem of the cheap production of isoprene as having now 

 been solved, as well as that of butadeine or erythrene. 



The influence of alkaline metals on butadeine was discovered 

 by Dr. Harries in the summer of 1910. According to his experi- 

 ments, by enclosing butadeine in a tube with sodium wire, the 

 butadeine after several hours completely disappeared ; a sub- 

 stance resembling rubber adhering to the wire. He also found 

 that isoprene was much more easily changed into rubber by 

 sodiun), than bj' mere heating. Regarding the substance thus 

 obtained. Dr. Harries, however, remarked : 



"These so-called 'sodium rubbers.' although physically acting 

 quite like rubber (for instance, permitting of vulcaniza- 

 tion) are not identical with other products, which correspond 

 with natural rubbers." 



WH.JiT IS ME.\XT BV ACTIWL RUBBER. 

 In dealing with this question. Dr. Harries takes the position 

 that the isoprene product must, like natural rubber, have tough 

 and elastic properties, must be soluble (neither too slowly nor 

 too easily) in freshly prepared ether, benzole or chloroform ; 

 and must, when kept for a certain time, gradually become hard 

 to dissolve. He adds that from the above comparison of natural 

 rubber with synthetic rubber from isoprene, he has come to the 

 conclusion that both are in a chemical sense identical ; the prod- 

 ucts of the polymerization of the same basic carbo-hydrate 

 (dimethylcyclooktadiene). Which exact isoprene formula cor- 

 responds most closely with natural rubber, is. he remarks, still 

 an open question : but he leaves aside for the present the con- 

 sideration of sodium rubbers, there being still uncertainty as to 

 their composition, and their not being identical with other 

 products, admittedly corresponding with the natural substance. 



FUTURE OF SYNTHETIC RUBBER. 

 Dr. Harries remarks in conclusion : 



"A wide field of chemical investigation is still offered here 

 . . . which may in the future be developed in the same way as 

 the chemistr>' of dye-stuffs. For every special purpose, its par- 

 ticular synthetic ruhlier will be manufactured. . . . 



''While the country has been viewing with anxiety the gradual 

 usurpation of German possessions by foreign nations, industrial 

 chemists have been quietly carrying out developments, which will 

 compensate our Fatherland, by rendering possible the domestic 

 manufacture of one of our most important colonial raw- 

 materials." 



TECHNIC.XL .\SPECTS OF SYNTHETIC Rl'BBER. 

 The paper read by Dr. Fritz Hofmann dealt with the technical 

 aspect of the question of sjnthetic rubber ; his position as Direc- 

 tor of the Laboratory of the "Farbenfabriken" of Elberfeld 

 (which establishment has occupied a leading position in the re- 

 cent investigations and experiments), naturallx' limiting his 

 statements to facts of a more or less generally known character. 

 In the first place, he dealt with the powerful elements at work 

 in developing the yield of Malayan rubber. 



Against these powerful forces, there has been arrayed a small 

 band of chemical experts. When the work of these pioneers 



commenced, there was but little prospect of a successful issue. 

 While the possibility of transforming isoprene into rubber by 

 polymerization, was referred to in technical literature, its advo- 

 cates had grown discouraged. Even Tildcn gave up working 

 upon the subject, failing to see the prospect of a successful re- 

 sult. Individuals being thus unequal to the task, it had to be 

 taken up by large chemical establishments, which besides abund- 

 ant capital, had the necessary staff of expert chemists. As many 

 as 300 are with the "Farbenfabriken" of Elberfeld, to the director 

 general of which (Privy Councilor Duisberg) Dr. Hofmann 

 paid a warm tribute of appreciation. Without the encourage- 

 ment of his example, the apostles of synthetic rubber must long 

 ago have had to give up the contest. 



DR. HOFMANN'S RESEARCHES. 

 Dr. Hofniann's' attention had been drawn to the subject about 

 six years ago. through reading a paper by Professor Dunstan of 

 London. As he discovered by the literature on the subject, that 

 isoprene was a constitutent of synthetic rubber, he perceived 

 that in order to make any progress it would be necessary to ob- 

 tain isoprene itself by synthesis, rather than, following the 

 method hitherto in vogue, to obtain it by the dry distillation of 

 rubber. This latter form of producing isoprene had been ex- 

 perimentally employed nearly a (|uartcr of a century ago by 

 Kondakow. but the quantity was too small to be of service. Hence 

 the necessity which Dr. Hofmann found of producing isoprene 

 on a large scale, in the highest degree of purity. The fulfillment 

 of this apparently simple requirement was. however, attended 

 with much difficulty. After two years' experimenting the right 

 path was found. As a basic material he had chosen coal, which 

 in this respect did not disappoint the expectations to which it 

 had given rise. Dr. Hofmann exhibited samples of the inter- 

 mediate products between coal and rubber, with a table showing 

 the sequence of the reactions of his process. .Acting on the prin- 

 ciples thus enumerated, Herr Coutelle, one of his colleagues, suc- 

 ceeded in March. 1909 in producing several quarts of pure syn- 

 thetic isoprene. The "Farbenfabriken" thus had at its disposal 

 the desired process ; the technical practicability of which was no 

 longer to be doubted. This process. Dr. Hofmann added, rested 

 upon a strictly scientific foundation ; he and his colleagues hav- 

 ing been convinced from the start, that only such a basis for their 

 work merited consideration. 



ACTION OF HEAT UPON ISOPRENE. 



.Mthough isoprene had thus been produced, the troubles of 

 the experts engaged in its production were not over. The first 

 question was: Out of this liquid resembling benzine, to form a 

 tough, elastic and "nervy" colloid, resisting all the influences to 

 which it would normally be subjected. A trial of muriatic acid 

 for this purpose only resulted in an oily chloride, but no trace of 

 rubber, .\nother experiment was with light, in accordance with 

 the statement of Wallach. that it would change isoprene into 

 a substance resembling rubber. However, after patiently waiting 

 eighteen months the only result was that the contents of the 

 bottle had assumed the consistency of a thin solution of sugar. 

 Under these circumstances all possible (and impossible) physical 

 and chemical agents were let loose on the isoprene. but it w^ould 

 not thicken. 



I'inally. Dr. Hofmann found in heat the power necessary for 

 producing the desired result. There was nothing new in heating 

 isoprene. but the result was new. It was also found that the 

 polymerizing effects of heat were promoted by certain chemical 

 additions. 



SYNTHETIC RUBBER PRODUCED. 



The first rubber produced by polymerization was obtained in 

 .August. 1909. in the laboratory of the Elberfeld "Farbenfabriken." 



