This substance is also known by the names, “Blue Vitriol” and “Blue
Stone.” It is a combination of sulphuric acid with oxide of copper,
and may be made by uniting those substances; but what is used on a
large scale for commercial purposes is obtained from the waters which
flow into copper mines where “copper pyrites” abound; this water
is evaporated, and the sulphate of copper crystallizes. Sulphate of
copper has of late been in great demand for the electro-deposition
of copper.