Abstract: In order to find an economical way to prepare sodium nitrate studies have been carried out on the reciprocal system Na⁺-NH₄⁺-Cl^--NO₃^--H₂O.Though the salt-pair of NaNO₃-NH₄Cl is a stable one,as the phase diagram shows, it is difficult to obtain pure NaNO₃ and NH₄Cl from it,for the solubilities of NaNO₃ and NH₄Cl vary with temperature almost in the same extent. A certain sort of optimum conditions has been approached at which the crystal of NaNO₃ is more heavy with that of NH₄Cl suspending in the solution, thus NaNO₃ can be easily separated from NH₄Cl.

Key words: sodium nitrate, common salt, double decomposition, transformation