The reaction between solid lead and chlorine gas

When lead reacts with a chlorine atmosphere the reaction rate shows a logarithmic rate law followed by a parabolic one. Both reaction rates can be explained by assuming that electron holes in the reaction product are rate-determining. In the beginning, the reaction of holes with lead (I) ions on lead ion lattice sites in PbCl₂ is the rate-determining step; later, the transport of holes by diffusion through the growing PbCl₂ layer becomes rate-determining.An oxide layer on the lead before chlorination retards the reaction, while, on the contrary, traces of oxygen in the chlorine gas accelerate the reaction. Both phenomena can be explained by assuming that a mixed compound PbO_1?xCl_2x is formed. It is concluded that the presence of impurities in the system may influence the reaction rate drastically.