INDIGO. 



15 



marked one A, the other B. No. 1 Flora I marked Remarks 



on East -India 



by E/' No. 2 Flora by the letter " D." indigo. 



As you intimated by your letter a desire that 

 these samples might be compared with Guatimala 

 indigo, I made the following experiment on each 

 of these four samples separately for that purpose. 

 Having reduced to a fine powder some of the 

 indigos A, B, C, D, and also some fine Guatimala 

 indigo, I dissolved a certain portion of each sepa- 

 rately in wine glasses, in equal quantities of con- 

 centrated vitriolic acid. I stirred them with glass 

 tubes during the solution, and when perfectly 

 digested, I added to each an equal quantity of 

 clear spring water. All these solutions thus di- 

 luted were full bright blue colours. 



This experiment, I think, fully indicates, that 

 the fecula, or colouring matter of these East-India 

 indigos, is of the same nature, and probably pro- 

 duced from the same species of plant as the Guati- 

 mala; the Carolina and West-India indigos usually 

 affording only brownish green colours by diges- 

 tion in vitriolic acid. 



The vitriolic solutions of the indigos A, B, C, 

 and D, being not distinguishable in brightness of 

 colour, and there not being a sufficient quantity of 

 each to allow me to dye with them separately, I 

 mixed these four solutions together, and by adding 

 thereto different proporions of water, &c. I dyed 

 therein the velveret patterns marked Nos. 1, 2, 



3 ; and 



