INDIGO

is a dye-stuff which exists in the leaf of plants of genus In dig of era, natural order Legumin ose, as a glucoside indican, Ci4H1706N3H20. An enzyme in the leaf acting on a water extract of the colorle glucoside in presence of atmospheric oxygen gives indigo tine, the coloring matter of indigo. About one-half per cent indigo is obtained from leaves and after evaporation sold as 3-in. cubes. A 20 per cent paste made by melting the carboxylic acid of phenyl glycocoll with caustic alkalies has supplanted the natural Indian product.