The current discussion about a unified scale of nuclidic masses and atomic weights * grew out of a desire to correct the indefiniteness of the chemical scale of atomic weights which results from variations in the isotopic composition of natural oxygen. Oxygen, with a defined atomic weight of 16, has been the universally accepted reference element for atomic weights since early in the present century. Earlier many chemists favored a scale based on hydrogen, with a definite atomic weight of unity. The hydrogen scale originated with Dalton and doubtless enjoyed support on the basis of Prout's hypothesis that the hydrogen atom is the structural unit in the atoms of all other elements. However, the operational advantages of oxygen in stoichiometric determinations of atomic weights offset the logical arguments for hydrogen and in time brought about the general acceptance of the oxygen scale. It was natural to assign a whole number, sixteen, to oxygen, rather than the nonintegral number representing its atomic weight on the hydrogen scale. Thus the unit of atomic weight became one‐sixteenth the weight of an atom of oxygen.