The structure of x%Na 2 O·(100−x)%SiO 2 glasses and melts (x=33, 40, 50, 55, 60, 67) was studied by in-situ Raman spectroscopy at temperatures from 293 to 1462K. The curve-fitting procedure was applied for data analysis taking into account the second coordination sphere of Si atoms. To obtain a correct interpretation of all bands in Raman spectra, additional types of structural units Q 12 , Q 21 and Q 32 were introduced into a description of the glass and melt structures. The conversion coefficients from characteristic Raman bands to concentrations of the corresponding structural units a 3 =1, a 2 =1.26, a 1 =1.53 and a 0 =2.56 are allowed in the determination of Q n -abundance in sodium silicate melts in the range from 0 to 67mol% Na 2 O. From these data the dependence of the equilibrium constants k n of the reactions 2Q n ↔Q n−1 +Q n+1 was determined. It was found that equilibrium constants for di- and metasilicate glasses, k 3 =0.015 and k 2 =0.07 are in close agreement with NMR studies. The k 3 and k 2 increase with increasing temperature up to 0.046 at 1243K and 0.14 at 1462K, respectively, which indicates an increase of the system disorder. The equilibrium constant of the reaction 2Q 1 ↔Q 2 +Q 0 was found to be 0.13±0.03.