Note 28 — Chapter XIV · THE VALENCY AND SPECIFIC HEAT OF THE METALS. MAGNESIUM. CALCIUM, STRONTIUM, BARIUM, AND BERYLLIUM
George Kamensky translation
Graham even distinguished the last equivalent of the water of crystallisation of the heptahydrated salt as that which is replaced by other salts, pointing out that double salts like MgK2(SO4)2,6H2O lose all their water at 135°, whilst MgSO4,7H2O only parts with 6H2O.