Comparison of chemical abundances as a function of H₂ column and number density. All plots are in log-log scales, and the symbol key is identical to that of Fig. 4. The solid lines indicate the least-squares fits to the data. Left: x(NH₃) versus N(H₂). The dashed line indicates the relationship found by Friesen et al. (2009, 2010) for Oph B2. Middle: x(NH₃) versus n(H₂). Right: NH₃/N₂H⁺ column density ratio versus N(H₂).