Critical re-examination of the reaction Cl + H2 ⇌ HCl + H

Recent data on the system Cl + H₂

HCl + H indicate that the rate constant ratio k₁/k₂ is a factor of two smaller than the equilibrium constant K. Two earlier explanations of this discrepancy are shown to be compatible with recent experimental and theoretical work. As an alternative explanation we suggest that flow tube measurements, ostensibly of k₂, actually determine 2k₂, due to Cl + H recombination on the walls of the flow tube. After correcting for this factor of two, all kinetic studies on this system are reconciled.