INDIGO. 



19 



run away. The blue precipitate is put into linen Remarks 



T . on East- India 



bags and drained from the superfluous moisture, indigo, 

 then taken out and placed in shallow wood cases 

 to dry, and afterwards cut in small squares, and 

 when perfectly dry packed in casks, boxes, or 

 skins, for sale. 



As an intelligent overseer is always necessary 

 to direct an indigo manufactory, the use of a ther- 

 mometer in the first process would enable him to 

 judge accurately of the state of the fermentation, 

 save him much trouble and anxiety, and prevent 

 the loss which frequently happens, from the indigo 

 liquor turning putrid and useless by being suf- 

 fered to overheat during the fermentation, through 

 want of a certain method to determine its heat. 



The use of the violent agitation in the second 

 process, I think, has never been clearly ascer- 

 tained in any account I have seen respecting 

 indigo. Its theory certainly depends upon the 

 great attraction which indigo in that state of 

 solution has for fixed air. By agitation and 

 exposure to the atmosphere, it absorbs it from 

 common air, unites with it, and is thereby precipi-. 

 tated. The success of this part of the business, 

 therefore, will be increased by such improvements 

 in mechanics, as will expose the coloured liquor 

 with the largest possible surface to the atmos- 

 phere, that the afiinity may sooner take place, and 

 in procuring a great circulation of common air, in 

 and about the reservoir, 



c 2 In 



