on a Substance possessing the Properties of Tannin. 295 
1. On one hundred grains of line indigo which had been put 
into a long matrass, one ounce of nitric acid diluted with an 
equal quantity of water was poured, and, as the action of the 
acid was almost immediate and extremely violent, another 
ounce of water was added. When the effervescence had nearly 
subsided, the vessel was placed in a sand-bath during several 
days, until the whole of the liquid was evaporated. 
On the residuum, which was of a deep orange colour, three 
ounces of boiling distilled water were poured, by which a con- 
siderable part was dissolved. 
The colour of the solution was a most beautiful deep yellow, 
and the bitter flavour of it surpassed in intensity that of any 
substance in my recollection ; it was examined by the following 
reagents. 
Sulphate of iron produced a slight pale yellow precipitate. 
Nitrate of lime only rendered it a little turbid, after which, 
a small portion of white powder subsided, which had the cha- 
racters of oxalate of lime. 
Muriate of tin produced a copious white precipitate, which 
afterwards changed to a yellowish-brown. 
Acetite of lead formed a very beautiful deep lemon-coloured 
precipitate, which possibly may prove useful as a pigment. 
Ammonia rendered the colour much deeper, after which the 
liquor became turbid, and a large quantity of fine yellow spi- 
culated crystals was deposited, which being dissolved in water, 
did not precipitate lime from its solutions. 
The flavour of these crystals was very bitter, and I suspect 
them to be composed of ammonia combined with the bitter 
principle first noticed by Welther.* 
* Thomson’s System of Chemistry, zd edit. Vol. IV. p. 246. 
