Extinction of dust mixed with molecular gas as a function of . The H₂ column densities were determined from UV observations toward stars, and the A_V(H₂) were determined from the nonlinearities of the E(B − V) versus N_H I relation (Eq. (3)). Green stars identify outlying points that were not considered in the fitting. At high column densities, A_V(H₂) is strongly correlated with , indicating that the nonlinear increase in dust reddening with respect to N_H I is induced by the presence of molecular gas. The orange curves were randomly sampled from the posterior distribution of the Markov chain Monte Carlo fitting, representing the fitting uncertainties. The green curve corresponds to the mean posterior profile that we employ to convert A_V(H₂) to (Eq. (6)).