Carbonic acid thermodynamic data

[linas]

I am looking for the heat of formation and Gibbs free energy of formation for carbonic acid (H2CO3) for both liquid and gas phase.

I couldn't find it in the CRC handbook of Chemistry.

I estimated the Gibbs free energy of formation of H2CO3 using the equilibrium constant for the hydration reaction: CO2(g) + H2O(l) --> H2CO3(l). But I would like to get the value from some theoretical/empirical data.

Thanks.