Vapor Pressures of the Polychlorinated Naphthalenes

The vapor pressures of the supercooled liquid P L for 17 polychlorinated naphthalene congeners were determined as a function of temperature with a gas chromatographic retention time technique. The method was calibrated with vapor pressure data for polychlorinated biphenyls (PCBs) which had been measured by other techniques. These data were employed to predict temperature-dependent vapor pressures for all polychlorinated naphthalenes (PCNs) from a regression with published retention time indices. Enthalpies of vaporization Δ VAP H and activity coefficients in 1-octanol were calculated for the PCNs and compared with those for polychlorinated biphenyls. Data analysis suggests that the dependence of P L and Δ VAP H on molecular size, as well as the partitioning behavior into 1-octanol of the PCNs, is very similar to that of coplanar PCBs, i.e., those congeners with no or only one chlorine substitution in the ortho positions. The affinity of these chemicals to 1-octanol increases with the degree of chlorination.