EXTRACTION OF INDIGO FROM WOAD. 305 



myself, to pointing out that which is the simplest, least 

 expensive, and most expeditious ; and which the most 

 constantly furnishes indigo of a uniform and good quality. 



No other apparatus is required in this process, than a 

 boiler for heating water, one tub for leaching, a second for 

 a receiver, and a bucket in which the water charged with 

 indigo is beaten to precipitate the fecula. 



The manner of operating, as described by M. Giobert, 

 author of the process, is as follows. 



Begin by heating the water till it boils. In the meao 

 time, place the leaves of woad (which have been cut 

 according to the signs of their fitness pointed out in the 

 process for making woad cakes) in the tub, taking care to 

 arrange them so that they shall not be anywhere crowded, 

 and that the distribution shall be equal throughout the 

 whole inside of the tub. Cover the tub with a hurdle of 

 osiers, or with a coarse net, and throw over it a coarse 

 woollen cloth. 



When the apparatus is thus arranged, pour boiling water 

 over the leaves till every portion of them be moistened, and 

 the water stand upon the top. Remove the woollen cloth 

 and the net, and stir the leaves gently, that the water may be 

 equally diffused through them, and may not descend to the 

 bottom of the tub, where it will not act upon them. 



Allow the leaves to rest during five or six minutes, and 

 then draw off the liquid through the stop-cock of the tub, 

 causing it to pass through a sieve into the receiver. If the 

 color of the liquid be too light, not having the depth of 

 well-charged new white wine, the flow of it must be 

 stopped, and that which has run out is to be again turned 

 upon the leaves, and allowed to remain until it has acquired 

 the appearance just mentioned. 



As soon as the liquor is drawn off, turn a fresh quantity 

 of warm water over the leaves, and allow it to act upon 

 them for the space of fifteen minutes. During this second 

 infusion, remove the water of the first leaching into the 

 bucket called the beater, and cause that of the second 

 leaching to flow into it, thus mixing the two. 



As the leaves are not by these two leachings exhausted 

 of all their indigo, cold water must now be turned upon 

 them ; and this may remain an hour or two. The liquor 

 of this third leaching is kept by itself, to be treated with 

 lime-water. After it has been drawn off, the leaves may 

 be strongly pressed, to obtain from them all the juice whici 

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