The abundances of He, N, Ne, Ar and Cl

The author examines various aspects of the abundance of the elements He, N, Ne, Ar and Cl. Results from forthcoming papers are summarized. There are two parts to this work. First is the examination of N/O and He/H ratios which show variations among nebulae. Second is the study of the element ratios Ne/O, Ar/O, Cl/O for which no, or infrequent variation would be expected. The unifying theme in this discussion is the examination of various ion ratios in planetaries as a function of nebular excitation or central star temperature. Though this means statements can be made regarding the kind of nebulae in which nitrogen enhancement occurs, the completeness of ionization of helium, and mean values for Ne/O, Ar/O and Cl/O. The method used avoids the problem of unobserved ions, and leads to what appears to be the quite accurate Ne, Ar and Cl abundances. (Auth.)