Knowledge of phase equilibria in the Na₂O–SiO₂ system at elevated temperatures is important for mastering the metallurgical process and for the glass and ceramic industries. The phase diagram at metasilicate and silica saturations in the Na₂O–SiO₂ system between 1173 and 1873 K has been investigated by quenching and phase analyses. The experimental technique involved equilibration of high purity oxide mixtures at sub-liquidus temperatures, rapid quenching in cold water and followed by compositional measurement of the phases using electron probe X-ray microanalyser. The phases stable in the equilibrium assemblages have been characterised over a wide range of compositions and temperatures. The results were compared with previous experimental data and an optimised phase diagram.