18 INTRODUCTORY 



indigo, first from benzene and acetic acid via phenylglycin, then from 

 naphthalene and acetic acid via anthranilic acid (a vital product) and 

 phenylglycin-orthocarboxylic acid, may be quoted as a most instruc- 

 tive illustration. The yield from the first of these generators was 

 insufficient for technological success ; the yield from anthranilic acid 

 is sufficient to enable the synthetical to compete successfully with the 

 natural product. In fact, most laboratory syntheses are at first accom- 

 plished without any consideration of the question of yield ; it is not 

 till the process is taken over by the technologist that this question 

 becomes of importance. The conversion of a laboratory compound 

 into a technological product often reacts also upon the scientific 

 investigation of the compound, leading not only to improvements in 

 methods of production, but likewise to the discovery of new synthetical 

 processes. 



The study of synthetical chemistry from the present point of view 

 will furnish numerous examples illustrative of the interdependence of 

 science and technology, and, in fact, many of the syntheses of vital 

 products effected of late years are the direct outcome of the techno- 

 logical value of such products. In view of the relationships between 

 biochemistry and chemical technology, the revelation of which, it is 

 claimed, is intimately associated with the present mode of treatment, 

 it is obvious that patented processes have had to be included in the 

 literature. It is of course beyond the scope of this work to discuss 

 such processes critically, and they have all been included, when having 

 any bearing upon any particular synthesis, for whatever they may be 

 worth industrially. The inclusion of patented processes cannot, how- 

 ever, but contribute towards the utility of the work from the point of 

 view of the chemical technologist. 



In one direction a certain latitude has been allowed in dealing with 

 synthesised vital products, to which special attention must be directed 

 in conclusion. In the case of optically active compounds the synthesis 

 is not logically complete till the optical isomeride has been isolated in 

 the laboratory by one or another of the known methods. Nevertheless 

 the synthesis of such optically active compounds has been recorded as 

 an accomplished fact, although the laboratory product is, as is well 

 known, always optically inactive through ' external compensation ' 

 (racemism, &c.). In going beyond the facts to this extent it is claimed 

 that the course adopted is, however, but a reasonable anticipation of 

 future discovery. The optically active vital product is actually present 

 in the racemic compound or mixture produced in the laboratory, and 

 it may confidently be expected that some method will hereafter be 

 devised for separating the optical isomerides in the case of synthesised 

 compounds which, being neither acid nor basic nor attackable by 

 biological methods, have thus far remained as unresolved. To illustrate 

 this point by a hypothetical case, dextrotartaric and racemic acids are 

 natural products, the latter alone being, strictly speaking, a synthetical 



