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Assuming that in the atmospheres of low-mass, metal-poor red giant stars, 1-Dmodels based on LTE accurately predict the abundance of iron from Fe II, wederive a globular cluster metallicity scale based on the equivalent widths ofFe II lines measured from high resolution spectra of giants in 16 key clusterslying in the abundance range -2.4 < [Fe/H]II < -0.7. We base the scale largelyon the analysis of spectra of 149 giant stars in 11 clusters by the Lick-Texasgroup supplemented by high-resolution studies of giants in five other clusters.We also derive ab initio the true distance moduli for M5, M3, M13, M92, and M15as a means of setting stellar surface gravities. We find that [Fe/H]II iscorrelated linearly with <W'>, the reduced strength of the near infra-red Ca IItriplet defined by Rutledge et al, although the actual correlation coefficientsdepend on the atmospheric model employed. We also discuss how to estimate[X/Fe]-ratios. We suggest that C, N, and O, as well as elements appearing inthe spectrum in the singly ionized state, e.g., Ti, Sc, Ba, La and Eu, shouldbe normalized to the abundance of Fe II. Other elements, which appear mostly inthe neutral state, but for which the dominant species is nevertheless theionized state, are probably best normalized to Fe I, but uncertainties remain.Comment: 23 pages + appendix + 4 figures + 17 tables = 61 pages; accepted by  PAS

A Globular Cluster Metallicity Scale Based on the Abundance of Feii