  Studying the global evolution of spiral galaxies requires determining their
overall chemical compositions. However, since spirals tend to possess gradients
in their chemical compositions, determining their overall chemical abundances
poses a challenge. In this study, the framework for a newly proposed method for
determining the overall oxygen abundance of a disk is established. By
separately integrating the absolute amounts of hydrogen and oxygen out to large
radii, the cumulative oxygen abundance is shown to approach an asymptotic
value. In this manner, a reliable account of the overall chemical state of a
disk is revealed.
