Take 16 pounds of coarsely ground indigo, and
4 pounds of sulphuret of arsenic; dissolve 22 pounds of sulphate
of iron in 6 gallons of water; introduce these three matters into the
indigo mill, and grind them for three days. If it be wished to have a
thickened blue, this mixture must have pounded gum added to it, but if
not, 5 gallons of water are added. This colour may be called blue No.
1.