What is pertaining to, or designating, a complex nitrogenous acid (C4H5N3O4) not known in the free state, but obtained, in combination with its salts, by a slow oxidation of uric acid, to which it is related called?

oxonic — Pertaining to, or designating, a complex nitrogenous acid (C4H5N3O4) not known in the free state, but obtained, in combination with its salts, by a slow oxidation of uric acid, to which it is related. (Webster's 1913.)

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