240 On the Manufacturing of Indigo in this Country. 



During the progress of this part of the business, particular atten- 

 tion should be paid to the smell of the liquor which weeps from the 

 aperture, for should it discover any sourness, it will be necessary to 

 let the fermenting liquor run immediately into the battery, and lime 

 water of sufficient strength must be added, until it has lost its sourness. 

 As it is running off it will appear green, mixed with a bright yellow 

 or straw color, but in the battery it will be of a beautiful green. 



Another maker has given the following description of the ferment- 

 ing process : 



When the plant is gathered, a large quantity is put into a vat, and 

 some wood laid above to prevent its rising above the water. The 

 mass begins to ferment sooner or later, according to the warmth of 

 the weather, and the maturity of the plant — sometimes in six or eight 

 hours, and sometimes in not less than twenty. The liquor grows hot, 

 throws up a plentiful froth, thickens by degrees, and acquires a blue 

 color inclining to a violet — at this time, without touching the herb, the 

 liquor impregnated with the tincture is let out, by cocks in the bot- 

 tom, into another vat placed for that purpose, so as to be commanded 

 by the first. 



The boiling process, for extracting the color from the dry plant, 

 was obtained from Mr. Dalrymple, who had for many years been 

 an extensive indigo maker in Bengal. He says : " take an iron, 

 brass, or copper boiler, fill it within three inches of the top with the 

 plants, press down with stones, and cover the plants with water. The 

 liquor must be heated, not until it boils, but until it begins to blubber, 

 or simmer. The water, by this time, will look greenish, then draw it 

 off into a shallow vessel or vat, and beat for one or two hours to in- 

 corporate oxygen with it. On taking some of the liquor in a white 

 saucer, litde particles will appear in it as big as a pin's head and smaller, 

 then stop beating and throw in a little lime water, upon which the 

 indigo will precipitate to the bottom, and the supernatant water will 

 look like brandy. The water has now to be drained off to a level 

 with the top of the sediment, lay the sediment on a cloth to drain, 

 and when stiff enough put it into moulds to dry." . 



The directions given by Mr. Dalrymple are evidently imperfect, 

 for none are given for the fermentative process, and those who are 

 in the least acquainted with the manufacture of indigo, must know, 

 that the coloring matter cannot be developed unless the liquor has 

 previously undergone a due degree of fermentation. 



