KC24was reacted with dehydrated benzene for a week at room temperature and then for a month at 70°C. The ternary K-Bz-GIC obtained at room temperature decomposed very slowly, when the sample was immersed in water. In case the ternary compound was heat treated at 70°C, the stability in water was very high. This unusual stability is due to the oligomerization of benzene, and hence we abbreviate the heat treated ternary compound as K-(Bz)n-GIC. The thermostability of K-(Bz)n-GIC was evaluated by XRD measurements and elemental analyses; the sample decomposed partly at 200°C and thoroughly decomposed to graphite at 200–400°C. The reaction of K-(Bz)n-GIC with NH3and Cl2gas are also discussed.