4i8 



SCIENCE PROGRESS 



At the same time, in spite of the drop in prices, the value of 

 the German exports of synthetic indigo increased : 



Exports of Synthetic Indigo from Germany 



Year. 



I8 95 

 1896 

 1897 

 1898 

 1899 

 I90O 

 I902 

 1904 

 I906 

 1908 

 I9IO 

 1912 



Value per ton. 

 (marks) 



6,289 



5,751 

 5,000 



3,493 

 2,461 



The normal price of 100 per cent, indigo before the war was 

 from M. 7.50 to M. 8.50 per kilo, compared with M. 15 to 16 

 charged in 1895 for the natural product. 



It might well have been expected that the " coup " obtained 

 by synthesising indigo would have been sufficient to encourage 

 the German firms to rest on their laurels, but so deeply is the 

 idea of research and progress engraved in the minds of the 

 German chemists and business men that the success was merely 

 an incentive to further discoveries. Improved methods of 

 dyeing with indigo were evolved based on exact scientific 

 knowledge of the chemical properties of the dye, and instead 

 of the old-fashioned " fermentation vats," in which the dye 

 was converted into a fit condition for use by allowing it to 

 ferment (in which process, incidentally, a considerable amount 

 of the dye was of necessity decomposed altogether and so lost), 

 the modern method of the hydrosulphite vat was introduced 

 and the necessary chemicals manufactured and sold at a cheap 

 rate. 



Further, having drawn level with nature by making her 

 choicest product in the chemical works, German chemists pro- 

 ceeded to beat her at her own game. 



Knowing the molecular structure necessary to produce 

 " vat-dyes," as they are termed, similar to indigo, analogous 

 compounds were made to determine their tinctorial value. 



