cripitation equation shown above. Alternatively, nitrogen dioxide is formed when concentrated nitric acid is added to copper turnings; in this case, substantial nitric oxide can also be produced. In either case, the resulting nitrogen dioxide exists in equilibrium with its dimer, dinitrogen tetroxide:2 NO2 ⇌ N2O4In order to remove either impurity, the gas mixture is condensed and fractionally distilled to give a mixture of NO2 and N2O4.[7] As the dimerisation is exothermic, low temperatures favour N2O4 as the dominant form.To improve the leaching process in the gold cyanidation, lead(II) nitrate solution is added. Although a bulk process, only limited amounts (10 to 100 milligrams lead(II) nitrate per kilogram gold) are required.[21][22] Both the cyanidation itself, as well as the use of lead compounds in the process, are deemed controversial due to the compounds' toxic nature.In organic chemistry, lead(II) nitrate has been used as an oxidant, for example as an alternative to the 