That comparative quantity by weight of an element which possesses the same chemical value as other elements, as determined by actual experiment and reference to the same standard. Specifically: (a) The comparative proportions by which one element replaces another in any particular compound; thus, as zinc replaces hydrogen in hydrochloric acid, their equivalents are 32.5 and 1. (b) The combining proportion by weight of a substance, or the number expressing this proportion, in any particular compound; as, the equivalents of hydrogen and oxygen in water are respectively 1 and 8, and in hydric dioxide 1 and 16.
Compare with normality. The amount of substance that gains or loses one mole of electrons in a redox reaction. The amount of substances that releases or accepts one mole of hydrogen ions in a neutralization reaction. The amount of electrolyte that carries one mole of positive or negative charge, for example, 1 mole of Ba2+(aq) is 2 equivalents of Ba2+(aq).