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reducing agent

1. n. [Enhanced Oil Recovery]
A chemical added to an acid to stabilize iron. The injected acid dissolves iron from rust, millscale, iron scales or iron-containing minerals in the formation. Iron can exist as ferric iron [Fe+3] or ferrous iron [Fe+2]. If the iron is not controlled, it will precipitate insoluble products such as ferric hydroxide and, in sour environments, ferrous sulfide [FeS], which will damage the formation. Reducing agents change or reduce Fe+3 to Fe+2 to avoid precipitation. Erythorbic acid is an effective reducing agent.