680 Professor H. E. Boscoe [May 27, 



WEEKLY EVENING MEETING, 



Friday, May 27, 1881. 

 William Bowman, Esq. LL.D. F.E.S. Vice-President, in tlie Chair. 



H. E. RoscoE, Esq. LL.D. F.R.S, &c. 



PRESIDENT OF THE CHEMICAL SOCIETY. 



Indigo, and its Artificial Production. 



More than eleven years ago the speaker had the pleasure of bringing 

 before this audience a discovery in synthetic chemistry of great interest 

 and importance, viz. that of the artificial production of alizarin, the 

 colouring substance of madder. To-day it is his privilege to point 

 out the attainment of another equally striking case of synthesis, viz. 

 the artificial formation of indigo. In this last instance, as in the 

 former case, the world is indebted to German science, although 

 to different individuals, for these interesting results, the synthesis of 

 indigo having been achieved by Professor Adolf Baeyer, the worthy 

 Buccessor of the illustrious Liebig in the University of Munich. Here 

 then we have another proof of the fact that the study of the most 

 intricate problems of organic chemistry, and those which appear to 

 many to be furthest removed from any practical application, are in 

 reality capable of yielding results having an absolute value measured 

 by hundreds of thousands of pounds. 



In proof of this assertion, it is only necessary to mention that the 

 value of the indigo imported into this country in the year 1879 

 reached the enormous sum of close on two millions sterling, whilst 

 the total production of the world is assessed at twice that amount ; so 

 that if, as is certainly not impossible, artificial indigo can be prepared 

 at a price which will compete with the native product, a wide field is 

 indeed open to its manufacturers. 



Indigo, as is well known, is a colouring matter which has attracted 

 attention from very early times. Cloth dyed with indigo has been 

 found in the old Egyptian tombs. The method of preparing and 

 using this colour is accurately described by both Pliny and 

 Dioscorides, and the early inhabitants of these islands were well 

 acquainted with indigo, which they obtained from the European indigo 

 plant, Isatis tinctoria, the woad plant, or pastel. With this they dyed 

 their garments and painted their skins. After the discovery of the 

 passage to India by the Cape of Good Hope, the eastern indigo, 

 derived from various species of Indigofera, gradually displaced woad, 

 as containing more of the colouring matter. But this was not 

 accomplished without great opposition from the European growers of 



