# equivalent weight

Equivalent weight is the weight of an element or compound which
combines with or displaces the equivalent weight of any other element or
compound; for an element, for an element it equals the relative
atomic mass (atomic weight) divided by the valence.
This presupposes the **law of equivalent proportions**, which
states that the ratio of the weights of two elements *A* and *B* which combine with the same weight of an element *C*, is the same
as the ratio of the weights of *A* and *B* which combine with
each other, or a small integral multiple of it. Since an element may have
more than one valence, and a compound may react in more than one way, they
may have more than one equivalent weight. The **normality** of a solution is its concentration in gram-equivalent weights per liter;
a solution whose normality is 1 is called normal.