Experimental determination of solubility and metastable zone width of ammonium dihydrogen phosphate in (NH4)2SO4Â + water and NH4FÂ + water systems

The solubilities of ammonium dihydrogen phosphate (MAP) were determined by dynamic method in the systems of (NH4)2SO4 + water and NH4F + 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 NH4F, and decreased with the adding of (NH4)2SO4 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 (NH4)2SO4 impurity and NH4F impurity on the supercooling temperature ΔTmax of MAP were studied. The MSZW of MAP were moved and enlarged by the two kinds of impurities mentioned above with different approaches.