| Abstract: | An experimental study is presented concerning solubility and primary nucleation kinetics of monohydrate citric acid from pure and selectively impure (KH2PO4, MgSO4 · 7H2O and FeSO4 · 7H2O) aqueous solutions. The metastable range of pure solutions is wide, ranging from 6 to 14°C, and the order of primary nucleation, equal to 2.51, is quite low. The addition of the tested impurities, which are usual fermentation aids, at concentrations lower than wt. 1%, produces negligible effects on the solubility and slightly enhances the primary nucleation rate. However, the presence of these compounds modifies the crystal habit at birth: in particular, the addition of MgSO4 · 7H2O and FeSO4 · 7H2O makes these crystals more elongated, but this effect diminishes as the crystals grow. |
