Note 9 — PART II.
Reading edition
Mr. T. P. Shepard gives in his valuable “Receipts for Calico Printing,” published in 1872, the following:—
NO. 52. INDIGO PRECIPITATE FOR FAST BLUE AND GREEN.
10 pounds quicklime, slacked with
6½ gallons water; then
2 pounds ground indigo finely rubbed in water are stirred in; then add
6 pounds copperas dissolved in 5 gallons of water; then add
5 gallons hot water and
15 gallons cold water.
Stir well from time to time, until the liquid has assumed a yellow color and deep blue veins or streaks appear on its surface. When this moment arrives, draw off the clear liquor, and precipitate every ten quarts of it with
½ pound tin crystals, dissolved in ½ pound muriatic acid.
To the remainder of the mixture of lime and indigo, 15 gallons of water may be added, and the whole stirred; and when settled, the indigo may be precipitated from the clear liquor as before. This operation may be repeated a second time before all the indigo is exhausted.
The indigo precipitate is to be collected on a muslin filter, and well squeezed out.