buffer, solution that can keep its relative acidity or alkalinity constant, i.e., keep its p H constant, despite the addition of strong acids or strong bases. Buffer solutions are frequently solutions that contain either a weak acid and one of its salts or a weak base and one of its salts. Many acid-base reactions take place in living organisms. However, for organisms to perform certain vital functions, the body fluids associated with these functions must maintain a constant p H. For example, blood must maintain a p H of close to 7.4 in order to carry oxygen from the lungs to cells; blood is therefore a powerful buffer.

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