Gold parting valens") could be made by the distillation of saltpetre (KNO) with alum (KAl(SO)) or vitriol (FeSO) with water. 2KNO + HO + FeSO → FeO + KSO + 2HNO Nitric acid, after distillation to increase the acid strength, is capable of dissolving the silver but it will not (by itself) dissolve the gold. However, nitric acid is not able to (fully) extract silver and other impurities from an alloy with a high content of gold. Therefore, one part of scrap gold was typically alloyed with three parts of copper (quartering) before parting with nitric acid. Another method uses Sterling silver
Brønsted–Lowry acid–base theory conjugate acid of the base in the first reaction and the conjugate base of the acid. In the above example, acetate is the base of the reverse reaction and hydronium ion is the acid. The power of the Brønsted–Lowry theory is that, in contrast to Arrhenius theory, it does not require an acid to dissociate. The essence of Brønsted–Lowry theory is that an acid only exists as such in relation to a base, and "vice versa". Water is amphoteric as it can act as an acid or as a base. In the image shown at the right one molecule of