9.4. (NH4)2HPO4 - NH4NO3 - H2O
There are two reports of the temperature and composition of the invariant points in the title system.2,4 However, while these two reports agree with respect to the temperatures of the invariant points, they do not agree about the compositions. For the invariant point at about 301.8 K they even disagree with respect to the nature of the equilibrium solid phase. In view of the region of existence of (NH4)2HPO2·2H2O (see p. 14) it is probable that the correct composition of the solid is that reported by Bergman and Velikanova,2 but additional experimental work is needed before any recommendation can be made about the composition of the invariant solutions. The isotherms measured at 323 K1 and 283 K3 cannot help to solve this problem.
References:
1
Kuznetsov, D. I.; Kozhukhovskiy, A. A.; Borovaya, F. E.; Zh. Prikl. Khim. 21, 1278 (1948).
2
Bergman, A. G.; Velikanova, L. V.; Zh. Neorg. Khim. 11, 2370 (1966).
3
Belyaev, I. N.; Sigida, N. P.; Stepanenko, T. D.; Zh. Prikl. Khim. 43, 178 (1970).
4
Torokhtey, L. P.; Ganz, S. N.; Braginskaya, R. I.; Izv. Vissh. Ucheb. Zaved.; Khim. Khim. Tekhnol. 15, 320 (1972).