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It is thus far from a certainty that natural indigo will dis- 

 appear from the market as soon as madder did when threatened 

 by German chemical competition. Indigo planters willing to 

 radically alter their old-time methods, improve their cultivation 

 of the crops and alter the mode of extraction of the dye, and 

 who by means of combination with official help, can make the 

 necessary sacrifice that the changes will entail may take heart 

 of grace. The last word has not been said yet on the subject 

 of natural indigo. 



Dr. Galmettes method of extracton. — Dr Calmette of Lille, has 

 patented the following process for the extraction of indigotine 

 from the plant. Hitherto the leaves of the indigo plant have 

 been placed in masonry vats in layers. The vats are then filled 

 to two-thirds with water, care being taken not to crush the 

 leaves. The leaves are held down by planks, and water is let in 

 to cover them. Fermentation then sets in, and the liquid, first 

 yellow becomes by degrees green. The temperature of the vat 

 rises, and soon the surface of the vat is covered by a film having 

 a metallic sheen. In this operation " indican," the substance 

 contained in the plant, transforms itself into gluCose and white 

 indigo under the influence of the fermentation caused by a 

 bacillus living on the leaf of the indigo plant. The white indigo 

 is transformed into blue indigo by simply beating up the liquid 

 bringing it into contact with air. 



A deposit of indigo flakes is formed at the bottom of the vats. 

 It is boiled up with water, dried, and made into small cakes. 

 The primitive method gave only about a third of the indigo 

 contained in the plant. There is a considerable loss owing to 

 the fermentation. Dr. Calmette has endeavoured to regulate 

 this fermentation he supresses it entirely, and treats the leaves 

 in close vats at a temperature of fifty to sixty degrees centi- 

 grade, unexposed to the oxygen of the air. The extraction of 

 the " indican " and its transformation into white indigo, takes 

 about two hours under the influence of a special ferment 

 " Diastase " hydrating and oxy dating, which exists in the cells 

 of the leaves. The liquid is then withdrawn from the warm 

 maceration, and is cooled with cold air by some mechanical 

 means. The white indigo becomes blue indigo but insoluble. By 

 these means three times more indigo is produced than by the 

 primitive method. The indigo thus obtained is very pure, and 

 contains from 80 to 82 per cent of indigotine, the colouring 

 matter of indigo." 



It will be noticed that the writer of the above article says : 

 " The last word has not been said yet about natural indigo.", 



