Patent ID: 6869731

Claim:
An electrolytic solution comprising an electrolyte which is an organic or inorganic acid, an additive which is a water-soluble N-containing heterocyclic compound, and a solvent which is water, wherein said water-soluble N-containing heterocyclic compound is at least one compound selected from imidazole and the derivatives thereof represented by the following formula (1); triazoles and the derivatives thereof represented by the following formula (2) or (3); and pyrazole and the derivatives thereof represented by the following formula (4): where R represents individually and independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an amino group, a carboxyl group, a nitro group, a phenyl group, a vinyl group, a halogen atom, an acyl group, a cyano group, a trifluoromethyl group, an alkyl sulfonyl group, or a trifluoromethylthio group.