On the Manufacturing of Indigo in this Country. 241 



I have been recently informed, that many first rate makers of in- 

 digo in Bengal condemn the process of obtaining it from the dried 

 leaves, on the plea that the article obtained is no better, and is much 

 less in quantity. If any of our planters should be disposed to try the 

 dry process, it will be necessary to inform them, that should the 

 leaves, between gathering and drying, be subject to fermentation, only 

 a small portion of coloring matter will be obtained, and that the 

 loss sustained will be as the degree of fermentation. 



During the precipitation of the coloring feculee the coarsest par- 

 ticles, possessing tlie greatest specific gravity, subside first, constituting 

 the lower strata of the pulp, and the lighter and finer particles sub- 

 siding the last, form the upper part. It is necessary that indigo ma- 

 kers should take advantage of this circumstance, by first taking off 

 the upper layer, and moulding it by itself, and the lower part by itself. 

 By this means they may obtain several qualities of indigo from one 

 mass of pulp. 



It appears from analysis made by Bergman, Quatremere, and 

 other chemists, that indigo of good quality does not contain more 

 than from 46 to 47 per cent of coloring matter, and that the very 

 best samples do not contain more than 48 per cent. 



The following table will exhibit an analysis of indigo of a good 

 quality, and of the menstruua in which the impurities are soluble. 

 Mucilaginous parts separable by water, - - - 12 

 Resinous parts soluble in alcohol, - - - - 6 



Earthy parts soluble in acetic acid, - - - - 22 

 Oxide of iron soluble in muriatic acid, - - - - 13 

 Coloring parts almost pure, - ^ - _ - 47 



100 



There cannot be a doubt, that manufacturers of indigo might pro- 

 duce, by attending to the analysis made by chemists, an article far 

 superior to any hitherto offered to the pubhc. It will also appear cer- 

 tain, when experience shall have confirmed the value of a superior 

 indigo, that a more than remunerating price could be obtained for a 

 purer article. For certain purposes a pure indigo would command 

 double, and even treble prices, provided the supply were not too great 

 for the consumption. This being the case, it would be well for our 

 manufacturers to pay some attention to the subject, and endeavor, by 

 some easy unexpensive process, to bring it to as great perfection as 



Vol. XVIII.— No. 2, 31 



