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
Acid–base reaction electrochemistry of molten salts. This definition describes an acid as an oxide ion () acceptor and a base as an oxide ion donor. For example: This theory is also useful in the systematisation of the reactions of noble gas compounds, especially the xenon oxides, fluorides, and oxofluorides. Mikhail Usanovich developed a general theory that does not restrict acidity to hydrogen-containing compounds, but his approach, published in 1938, was even more general than Lewis theory. Usanovich's theory can be summarized as defining an acid as anything that accepts negative species or donates positive ones, and a base as the reverse. This