(427) 
ON 
THE NATURE AND PROPERTIES 
OF 
INDIGO; 
WITH DIRECTIONS FOR THE VALUATION 
OF 
Different Samples. 
BY JOHN DALTON, F. BR. S. $e. 
(Read November 14th, 1823.) 
WeE owe the first good approximation to 
the chemical analysis of the Indigo of com- 
merce to Bergman. According to his ex- 
periments, the best samples of Indigo yielded, 
by analysis, the following principles: 
47 pure Indigo 
12 Gum 
6 Resin 
22 Earth 
13 Oxide of Iron 
100 
A subsequent analysis of Indigo made by 
Chevreuil, (Annal. de Chimie, tom. 68) gives 
45 per cent. of pure indigo in the best Guati- 
mala indigo, and the foreign matters much 
