PIV measurements in a liquid-liquid system at volume percentages up to ten percent dispersed phase

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Primary nucleation of salicylamide: the influence of process conditions and solvent on the metastable zone width

The onset of nucleation of salicylamide in organic solvents has been measured for a total of 2911 nucleation experiments at a constant cooling rate. The experiments are divided into series of different experimental conditions and for each series, the mean values and distributions of the nucleation events have been recorded. Generally, a significant spread in the onset of nucleation among identical repeated experiments was observed. The solvent and the cooling rate were found to be the factors exerting the greatest influence on the onset of nucleation, whereas the expected effects of the solution volume and the saturation temperature were largely absent. A correlation is observed between the supersaturation ratio at the average onset of nucleation and a group of parameters extracted from the pre-exponential factor in the classical nucleation rate equation, which is in agreement with the concept that a higher attachment frequency facilitates nucleation. It is also found that there can be a profound difference in the metastable zone width between experiments in open and closed crystallizers

Thermodynamics and nucleation kinetics of m-aminobenzoic acid polymorphs

The polymorphism of m-aminobenzoic acid has been investigated, Two polymorphs have been identified and characterized by X-ray powder diffraction (XRPD). Fourier transform IR (FTIR), microscopy, and thermal analysis. The melting properties and isobaric heat capacities of both polymorphs have been determined calorimetrically and the solubility each polymorph in several solvents at different temperatures has been determined gravimetrically. the solid-state activity i.e., the Gibs free energy of fusion) of each polymorph has been determined through a comprehensive heterodynamic analysis based oil experimental data. It is found that the polymorphs are enantiotropically related, with a stability transition temperature of 1-56.1 degrees C. Thc published crystal Structure belongs to the polymorph that is metastable at room temperature. Energy-temperature diagrams of both polymorphs have been established by determining the free energy. enthalphy, and entropy of fusion as a function of temperature. A total of 300 cooling crystallizations have been carried out at constant cooling rate using different saturation temperatures and solvents. and the visible Onset of primary nucleation was recorded. The results show that for this Substance the polymorph that will nucleatic depends chiefly on the solvent. In water and Methanol solutions the stable form I was obtained in all experiments, whereas in acetonitrile, a majority of nucleation experiments resulted in the isolation of the metastable form II. It is shown how this call be rationalized by analysis Of Solubility, solution speciation. and nucleation relationships. The importance of carrying out multiple experiments at identical conditions in nucleation Studies of polymorphic systems is demonstrated

Thermodynamics and nucleation of the enantiotropic compound p-aminobenzoic acid

In this work, the thermodynamic interrelationship of the two known polymorphs of p-aminobenzoic acid has been explored, and primary nucleation in different organic solvents investigated. The solubility of both polymorphs in several solvents at different temperatures has been determined and the isobaric solid-state heat capacities have been measured by DSC. The transition temperature below which form alpha is metastable is estimated to be 16 degrees C by interpolation of solubility data and the melting temperature of form beta is estimated to be 140 degrees C by extrapolation of solubility data. Using experimental calorimetry and solubility data the thermodynamic stability relationship between the two polymorphs has been estimated at room temperature to the melting point. At the transition temperature, the estimated enthalpy difference between the polymorphs is 2.84 kJ mol(-1) and the entropy difference is 9.80 J mol(-1) K-1. At the estimated-melting point of form beta the difference in Gibbs free energy and enthalpy is 1.6 kJ mol(-1) and 5.0 kJ mol(-1), respectively. It is found that the entropic contribution to the free energy difference is relatively high, which explains the unusually low transition temperature. A total of 330 nucleation experiments have been performed, with constant cooling rate in three different solvents and with different saturation temperatures, and multiple experiments have been carried out for each set of conditions in order to obtain statistically significant results. All performed experiments resulted in the crystallization of the high-temperature stable alpha-polymorph, which is kinetically favoured under all evaluated experimental conditions. The thermodynamic driving force required for nucleation is found to depend chiefly on the solvent, and to be inversely correlated to both solvent polarity and to solubility