Colloidal dispersions of sodium and potassium phosphates in a hydrocarbon medium have been synthesized by reacting, under specific conditions, aqueous sodium or potassium hydroxyde with tetraphosphorous decasulfide in hydrocarbon solvent in the presence of a surfactant such as alkylarylsulfonic acid. The resulting products can be defined as a distribution of inorganic particles stabilized by sodium or potassium alkylaryl sulfonate in a reverse-micelle type association. The chemical structures of the mineral cores are determined using 31P NMR, potentiometric titration and elemental analysis. The core particles were found to be respectively a mixture of sodium (poly)phosphates and a mixture of potassium (poly)phosphates. Inorganic core and organic surfactant balances were determined using thermogravimetric analysis. The weight ratio of mineral core part to organic surfactant part is found about to be 1.6 for Na derivative and 2.4 for K derivative. The morphological characterization of the colloidal dispersion has been investigated using Small Angle X-ray Scattering, Transmission Electron Microscopy and Wide Angle X-ray Scattering. The inorganic particles appear as cristallized particles with diameters ranging from 50 to 360 Angstrom.