474 DTES AND COLORING STUFFS. 



pierced, a few inches in diameter. These are closed with plugs during the beat- 

 ing, but two or three hours after it, as the indigo subsides, the upper plug is 

 withdrawn to run off the supernatant liquor, and then the lower plugs in succes- 

 sion. The state of this liquor being examined, affords an indication of the 

 success of both the processes. When the whole liquor is run off, a laborer 

 enters the vat, sweeps all the precipitate into one corner, and enters the 

 thinner part into a spout which leads into a cistern, alongside of a boiler, 

 twenty feet long, three feet wide, and three feet deep. "When all this liquor is 

 once collected, it is pumped through a bag, for retaining the impurities, into the 

 boiler, and heated to ebullition. The froth soon subsides, and shows an oily 

 looking film on the liquor. The indigo is by this process not only freed from 

 the yellow extractive matter, but is enriched in the intensity of its color, and 

 increased in weight. From the boiler the mixture is run, after two or three 

 hours, into a general receiver called the dripping rat, or table, which, for a 

 factory of twelve pairs of preparation vats, is twenty feet long, ten feet wide, 

 and three feet deep, having a false bottom two feet under the top edge. This 

 cistern stands in a basin of masonry (made water-tight with Chunam, hydraulic 

 cement), the bottom of which slopes to one end, in order to facilitate the drain- 

 age. A thick woollen web is stretched along the bottom of the inner vessel, 

 to act as a filter. As long as the liquor passes through turbid, it is pumped 

 back into the receiver ; whenever it runs clear, the receiver is covered with 

 another piece of cloth to exclude the dust, and allowed to drain at its leisure. 

 Next morning the drained magma is put into a strong bag, and squeezed in a 

 press. The indigo is then carefully taken out of the bag, and cut with a brass 

 wire into bits, about three inches cube, which are dried in an airy house, upon 

 shelves of wicker work. During the drying a whitish effloresence comes upon 

 the pieces, which must be carefully removed with a brush. In some places, 

 particularly on the coast of Coromandel, the dried indigo lumps are allowed to 

 effloresce in a cask for some time, and when they become hard they are wiped 

 and packed for exportation. 



2. Indigo from dried leaves, The ripe plant being cropped, is to be dried in 

 sunshine from nine o'clock in the morning till four in the afternoon, during two 

 days, and threshed to separate the stems from the leaves, which are then stored 

 up in magazines till a sufficient quantity be collected for manufacturing opera- 

 tions. The newly dried leaves must be free from spots, and friable between the 

 fingers. When kept dry, the leaves undergo, in the course of four weeks, a 

 material change, their beautiful green tint turning into a pale blue-grey, previous 

 to which the leaves afford no indigo by maceration in water, but subsequently a 

 large quantity. Afterwards the product becomes less considerable. 



The following process is pursued to extract indigo from the dried leaves : 

 They are infused in the steeping vat with six times their bulk of water, and 

 allowed to macerate for two hours, with continual stirring, till all the floating 

 leaves sink. The fine green liquor is then drawn off into the beater vat, for if 

 it stood longer in the steeper, some of the indigo would settle among the leaves 

 and be lost. Hot water, as employed by some manufacturers, is not necessary. 

 The process with dry leaves possesses this advantage, that a provision of the 

 plant may be made at the most suitable times, independently of the vicissitudes 

 of the weather, and the indigo may be uniformly made ; and', moreover, that the 

 fermentation of the fresh leaves, often capricious in its course, is superseded by 

 a much shorter period of simple maceration. 



PRODUCTION OF INDIGO IN INDIA. 



maunds. maunds. 



1840 120,000 



1841 162,318 



1842 79,000 



1843 143,207 



1814 127,862 



1845 127,862 



1846 101,328 



1847 110,000 



1848 126,565 



1849 126,000 



Average of the ten years 126,744 maunds. 



The yield from the. different districts in 1849, was nearly as 

 follows : 



