Woollen goods are first dyed blue with indigo, and afterwards with sumac, logwood, and green or blue copperas.
|blue vitriol |
A blue, crystalline compound of copper sulfate. Blue vitriol is soluble in water, and is a very important industrial salt of copper. It is used in insecticides and germicides, in electrolytes for batteries, and in electroplating baths. Chemical formula: CuSO4·5H2O.