Fundamental evolution characteristics of alkali metal compounds, especially sodium compounds in coal combustion/gasification were experimentally studied using a rapidly heated batch reactor under a wide range of temperature conditions. Six types of coal with different properties were reacted in the reactor. The evolution characteristics of sodium compounds obtained experimentally were compared with those predicted using both coal properties of cross-correlation coefficient between sodium and silicon in the raw coal and the fraction of condensed sodium aluminosilicates in the residue, calculated by the thermochemical equilibrium theory. The reason why the two indices were selected is that the sodium aluminosilicates was detected by X-ray diffraction analysis in the residue. The cross-correlation coefficient between sodium and silicon in the raw coal is calculated using two digital images of sodium and silicon distributions obtained by the Energy dispersed X-ray (EDX) analysis at the cross-section of raw coals. On the other hand, the chemical equilibrium calculation is performed by prescribing the experimental conditions and ultimate analysis data and ash compositions of the coal. The results predicted correlated well with the experimental data even when the evolution characteristics of sodium was dependent on the coal type and when the experimental conditions were varied widely. The coal with low cross-correlation coefficient between sodium and silicon and low fraction of condensed sodium aluminosilicates in the residue was found to release sodium compounds. Both of the two indices proposed can contribute to the prediction of fundamental evolution characteristics of alkali metal compounds in the coal combustion/gasification.