The properties of atmospheric aerosol organic compounds are often simulated in models by arbitrarily choosing model compounds which have, in most cases, little contact with the physical reality. We propose here a proce-dure with which to derive a simplified model of the water sol-uble organic fraction of the atmospheric aerosol. Quantita-tive measurements of organic carbon concentration and pro-ton concentration of the main functional groups contained in the aerosol water soluble organic compounds (WSOC) mix-ture are used to formulate a set of a few model compounds, representative of the whole WSOC mass, which can simu-late in models the chemical and physical properties of aerosol WSOC.