The reaction behavior of sodium chloride socialite Na-8[AlSiO4](6)Cl-2 in ammonium chloride solution has been investigated under mild hydrothermal conditions (T = 473 K) for reaction times up to 72 h. Reactions under weak acid conditions led to an amorphous aluminosilicate phase comparable to a leaching process. This material forms an amorphous layer around the sodalite grains, preventing the framework from further decomposition. About 52% of sodalite was damaged by acid leaching after I I hours and this amount remains nearly constant even at longer reaction periods up to 72 hours. Cation exchange was observed in sodalite only on a very low level (< 10%). Beside these reactions under acid conditions (pH = 5) some additional experiments in alkaline solutions were done to improve ion exchange of sodalite. Thus an ammonium/ammonia buffer solution was used (pH approximate to 9) at various temperatures in a range of 353 - 473 K. Neither cation exchange nor decomposition of the sodalite was obtained at 353 and 393 K after 72 hours. Formation of amorphous material started at 433 K. In contrast to the acid conditions a total transformation of sodalite into a crystalline ammonium aluminosilicate phase was observed at 473 K.