Note 2 — Chapter XXIV · COPPER, SILVER, AND GOLD

Cupric sulphate contains 5 molecules of water, CuSO4,5H2O, and the isomorphous mixtures with ZnSO4,7H2O contain either 5 or 7 equivalents, according to whether copper or zinc predominates (Vol. II. p. 6). If there be a large proportion of copper, and if the mixture contain 5H2O, the form of the isomorphous mixture (triclinic) will be isomorphous with cupric sulphate, CuSO4,5H2O, but if a large amount of zinc (or magnesium, iron, nickel, or cobalt) be present the form (rhombic or monoclinic) will be nearly the same as that of zinc sulphate, ZnSO4,7H2O. Supersaturated solutions of each of these salts crystallise in that form and with that amount of water which is contained in a crystal of one or other of the salts brought in contact with the solution (Chapter XIV., Note 27).