The kinetics and the position of the equilibrium of the reaction Co2(CO)8+H2⇄2 HCo(CO)4 were studied in the range of 80–160 °C and 50–100 atm. by means of in situ IR spectroscopy. The reaction is reversible first order with respect to CO2(CO)8 and HCo(CO)4 and the energies of activation of the forward and the reverse reaction are found to be 17,3 cal/mole, and 11.0 kcal/mole resp. The reaction is slightly endothermic with ΔH=6.6 kcal/mole and ΔS=14.6 e.u. The heat of formation of HCo(CO)4 and the bond strength between hydrogen and cobalt in HCo(CO)4 were found to be—146.1 kcal/mole and 54.7 kcal/mole resp.