PRESIDENTS ADDRESS. XV11 



cular weight of 1213 truly a masterpiece of synthetic skill. Now 

 a remarkable fact is that these polypeptides have properties which 

 are quite different from those of the amino-acids of which they 

 are made up and approach closely the properties of proteins. They 

 give, for example, some of the characteristic reactions of the 

 proteins, and when they are fed to animals the products are the 

 same as in the case of albumens. These results indicate that the 

 advances now being made so rapidly are in the right direction and 

 that the goal of the strenuous efforts being made, the synthesis of 

 a veritable protein, is not beyond the powder of organic chemistry. 



In turning now to the group of vegetable dyes we leave pure 

 science behind and deal with science in partnership with com- 

 merce and industry. For unlike the monosaccharoses and poly- 

 peptides with which we have been dealing, alizarin and synthetic 

 indigo are articles of commerce which have competed with, and 

 displaced, the vegetable dyes madder and indigo. Alizarin was 

 the first but indigo is the greatest achievement of synthetic 

 chemistry in this field. Many syntheses of it have been long known, 

 the first having been effected in 1870. The problem of the com- 

 mercial synthesis of indigo, however, involved other factors 

 besides the purely scientific ones; and its solution is a magnificent 

 tribute not only to the synthetic skill and the perseverance, but 

 also to the business sagacity, of those workers who for twenty 

 years never faltered in their determination 'to reach the desired goal. 



The first attempts to place the synthesis of indigo on a com- 

 mercial basis started from toluene, one of the constituents of coal 

 tar, as raw material. From this substance there are numerous 

 paths leading to indigo. Some of these perpetually lured the 

 investigator on with the hope, so often elusive, that means could 

 be devised of reducing the cost of production to such an extent 

 as fto make the route a commercial one. One of these routes led 

 to indigo through a substance called authranilic acid. Then forth- 

 with the dominant factor in the problem became the production 

 of this acid at a sufficiently reduced cost. A method of making it 

 from napthalene instead of from toluene was discovered, and 

 this discovery was the turning-point of the struggle. "At one 

 stroke" says one of the investigators 1 "the commercial manu- 



1 H. Brunk, Chem News (1902), 89, 212. 

 PROC. & TRANS, N. S. IN T ST. Sci. VOL. XIII. PROC. B. 



