200 Cultivation and Manufacture of hidigo, [Jut* 



" After the leaves have been kept a sufficient time, they are trans- 

 ferred to the steeping vat, which is an uncovered reservoir, built of 

 brick work, and lined with Roman cement, or stucco prepared from 

 burnt shells, and filled with water. They remain there for two hours, 

 and are every now and then turned ; after which, the water having 

 acquired a fine green colour, is run off, and passed, through strainers 

 into the beating vat. Two hours may appear to be a very short time 

 for infusing the leaves. It has been found, however, that when the 

 process is prolonged beyond this, a partial precipitation of the Indigo 

 takes place. 



" The liquor, when in the beating vat, is agitated by paddles for 

 about two hours, daring which the fine green colour gradually darkens, 

 and acquires a blackish blue. As soon as this last hue appears, and the 

 froth thrown up in beatingbecomes more or less white, and the incipient 

 separation of the particles of Indigo can be detected, a certain propor- 

 tion of lime water is well mixed with the liquor, and the whole is allow- 

 ed to settle. In the course of three hours the indigo w-ill have fallen 

 to the bottom, and the supernatant liquid, which ought to be of a fine 

 Madeira colour, is allowed to run off by means of cocks, placed at 

 dilTerent heights. The indigo is, after this, conveyed into the covered 

 part of the laboratory, where it is spread on strained cloth, and allow- 

 ed to drain. 



" On the following morning, the Indigo is put into a copper, with 

 a quantity of hot water, and fire is applied. As the mass lieatens, a 

 quantity of scum rises, which is immediately removed, and, as soon as 

 the whole is brought to the boiling point, the fire is w-ithdrawm. The 

 Indigo is then again taken to the strainers, and having been again 

 drained, it is well worked with the hands, and afterwards subjected to 

 pressure in square boxes, in order to get rid of as much moisture as 

 possible. In this manner large square cakes, about 2h inches in thick- 

 ness, are formed, which are subsequently divided into smaller cakes, 

 and allowed to dry gradually in the shade. 



" The boiling process, although not generally adopted, is said to 

 improve very considerably the quality, and enhance the value of the 

 produce. 



" A beautiful yellow precipitate may be obtained, by means of acetate 

 of lead, from the Madeira-coloured liquid, drawn off in the beating vat. 

 This is said, by Mr. Weston, to promise to supply a great desideratum 

 —a permanent yellow dye. Experiments are, however, wanting to 

 confirm this. 



