Studies on the vapor behavior of selected polychlorinated biphenyls

The vapor loss of several PCB isomers from stainless steel planchets surfaces has been studied. Experiments were carried out under two different conditions. In one case, the vapor loss was observed from 2 molecular layers of PCB, while in the other series, the loss from approximately 200 molecular layers was observed. In both cases the loss of PCB from the surface was substantial, although the controlling mechanism of vapor loss was different. In the first case, the transport was approximated by a simple first order rate law, whereas in the latter case, it was a diffusion controlled process. In general, the vapor loss decreased with increasing number of chlorine atoms present in the isomer. The 4,4(1)-dichlorobiphenyl showed a deviation as compared to others indicating that such factors as the electronic distribution, position of chlorine atom on the biphenyl ring and symmentry of the molecule are also important in discussing the vapor transport.