RUBBER 373 



the production of butadiene are in practice open to various 

 modifications. Further research is necessary to determine which 

 of these methods and what details must be adopted to give the 

 best results from the commercial point of view. It must be 

 borne in mind in considering the fermentation process just out- 

 lined, that, in addition to the butyl alcohol required for making 

 rubber, acetone is the other product. This liquid, hitherto 

 obtained from acetic acid, a product of the destructive distilla- 

 tion of wood, is a solvent which has much increased in value 

 since its employment in making cordite. This by-product then 

 may become so profitable as to reduce the cost of butadiene 

 rubber considerably, and so assist the synthetic in competition 

 with the natural rubber. 



A more recent patent taken out in Germany starts from 

 acetone, which is first subjected to the action of fuming sulphuric 

 acid, and ethylene gas is then passed into the liquid at a tempera- 

 ture of 100 to 110 C. Isoprene is said to be formed together 

 with caoutchouc which is the product of its polymerisation. 

 From 6 parts of acetone, 5 parts of raw caoutchouc, with 1J 

 parts of isoprene, and other volatile products are stated to have 

 been produced. Homologues of acetone, such as diethyl-ketone, 

 are included in the patent (India-rubber Journal, Nov. 6th, 1915, 

 p. 12). Many of these attempts are not likely to be successful 

 from the commercial point of view, but the frequent recourse 

 to patent protection is an indication that chemists are still busy 

 with the problem. 



The production of synthetic alizarin and indigo, and the in- 

 fluence of the resulting manufacture of these dyes on the cultiva- 

 tion of the madder and indigo plants respectively, have been 

 discussed in many quarters as indicating the possible fate of the 

 rubber plantations which, during the last twenty years, have 

 extended over very large areas of land in the East. The case of 

 rubber, however, appears to present one feature in which it 

 differs from the position of madder and indigo. For these two 

 materials the demand though very large is limited, whereas the 

 uses of rubber multiply in the imagination of anyone who 

 seriously considers the question. 



Should the many difficulties at present attending the several 

 synthetic processes be successfully overcome, the first effect 

 would probably be a fall in the price of rubber generally, but it 

 would then find applications on a scale much greater than 



