The number of parts by weight of an element or compound which will combine with or replace, directly or indirectly, 1.008 parts by weight of hydrogen, 8.00 parts of oxygen, or the equilvalent weight of any other element or compound. The term equivalent weight comes from the law of equivalent proportions, which states that the weights of two elements A and B which combine separately with identical weights of another element C are either the weights in which A and B combine together, or are related to them in the ratio of small whole numbers. A standard weight of 8.000 parts is chosen for oxygen. For all elements, the atomic weight is equal to the equivalent weight times a small whole number, called the valence of the element.