164 



GREEN INDIGO. 



CiTAP. VIII. 



ON A GREEN COLOURING MATERIAL PRODUCED IN 

 CHINA. 

 By Mons. J. Persoz. 



I HAVE the lionoiir to place before the Academy a spe- 

 cimen of a colom-ing material used in China as a green 

 ' dye for textile fibres. With the permission of the Academy _ 

 I will briefly state how I was led to a knowledge of the 

 existence of this dye. 



Mons. Daniel Koechlin-Schouc forwarded to me last 

 antumn a specimen of calico dyed in China, of a rich and 

 very permanent green, mth a request that I should en- 

 deavoiu' to ascertain the composition of the green colour. 

 Every attempt that I made upon the specimen to detect 

 evidence of the presence of a blue or yellow failed, and I 

 was led to the conviction, by isolating the colouring prin- 

 ciple, that the green was produced by a dyeing material 

 of a peculiar nature and sui generis. It further was 

 evident, — 



1st. That the colouring matter was an organic product 

 of vegetable origin ; 



2nd. That the fabric on which it was fixed was charged 

 with a strong dose of alum and a little oxide of iron and 

 lime, bodies the presence of which necessarily implied that 

 mordants had been used m ^dyeing the calico. 



These results were so positive, and at the same time so 

 opposed, not only to everything known in Europe regard- 

 ing the composition of green colour, but also to all that 

 is recorded by writers regarding the dyeing processes 

 employed in China for the production of green, that I 

 was uiduced to go into a more detailed investigation of 

 the subject ; and about the end of last November I 

 applied to Mr. Forbes, the American consul at Canton, 

 for some of this valuable material. I am indebted to his 

 kindness for a specimen weighing about one gramme 

 (151 grains). 



The substance is met with in thin plates, of a blue 



