Experimental determination of solubility and metastable zone width of ammonium dihydrogen phosphate in (NH4)2SO4 + water and NH4F + water systems.

The solubilities of ammonium dihydrogen phosphate (MAP) were determined by dynamic method in the systems of (NH 4 ) 2 SO 4 + water and NH 4 F + water at the temperatures of 293.2–343.2 K at an atmospheric pressure, and the experimental data was fitted by the modified Apelblat equation. The result showed that the solubilities of MAP increased with temperature and the adding of the NH 4 F, and decreased with the adding of (NH 4 ) 2 SO 4 within the measurement range. The metastable zone width (MSZW) of MAP was measured by the focused beam reflectance measurement (FBRM) during cooling crystallization process. The effects of the (NH 4 ) 2 SO 4 impurity and NH 4 F impurity on the supercooling temperature ΔT max of MAP were studied. The MSZW of MAP were moved and enlarged by the two kinds of impurities mentioned above with different approaches. [ABSTRACT FROM AUTHOR]