摘要
The phase diagram of system Na<sub>2</sub>O-Al<sub>2</sub>O<sub>3</sub>-H<sub>2</sub>O has been investigated by many authors. The left part （Al<sub>2</sub>O<sub>3</sub>·3H<sub>2</sub>O as solid phase） of the diagram of Na<sub>2</sub>O-Al<sub>2</sub>O<sub>3</sub>-H<sub>2</sub>O system is of no problem, but the right part （hydrated sodium aluminates as solid phases） is in controversies. Jucaitis concluded that there were two hydrated sodium aluminates, i.e. Na<sub>2</sub>O·Al<sub>2</sub>O<sub>3</sub>·2.5H<sub>2</sub>O and 3Na<sub>2</sub>O·Al<sub>2</sub>O<sub>3</sub>·6H<sub>2</sub>O. Kuznetsov suspected the existence of the latter and believed that it was actually a mixture of Na<sub>2</sub>O·Al<sub>2</sub>O<sub>3</sub>·2.5H<sub>2</sub>O
