Separation in two solid phases on freezing could be expected for binary eutectics compounds, but the specific arrangement of the two phases in the solid is unknown. The problem is more complexly exciting when the sample is a composite, elaborated by graphite and an inorganic salt.

Energy dispersive x-ray microanalysis (EDS) based on scanning electron microscopy (SEM), SEM/EDS, allowed the observation in depths of 1-2 microns. The backscattered electrons, emitted from the depth of a sample illustrated readily the chemical phase difference between particles and the composite (BEI image, red pointer, Table 4.). Evidently, some small crystallites of single K and Na components of the salt avoided the melting process and formed solidified mechanical mixtures.