The solubility of carbon dioxide in aqueous solutions of piperazine was determined at low gas loadings (stoichiometric molar ratios of carbon dioxide to piperazine between about 0.05 and 0.95) and temperatures between (313 and 393) K by means of headspace gas chromatography. The stoichiometric molality of piperazine amounted to about (1 and 2) mol center dot(kg of water)(-1) {mass fraction of piperazine approximate to (8 and 15) %} at T approximate to 313 K and to about (2 and 4) mol center dot(kg of water)(-1) {mass fraction of piperazine approximate to (15 and 26) %} at T approximate to (353 and 393) K. The partial pressure of carbon dioxide was between about (0.1 and 95) kPa. A thermodynamic model for describing the vapor-liquid equilibrium (which applies Pitzer's molality scale based equation for describing the Gibbs excess energy of the aqueous phase) is revised and extended using the new data.