Determination of the metastable zone and induction time of thiourea for cooling crystallization

The solubility,metastable zone width(MSZW),and induction time of thiourea for cooling crystallization were experimentally determined in the temperature range of 283-323 K.The solubility data could be well described by the Apelblat equation model as lnx=-99.55+1071.66/T+16.27 lnT.The determinations of the effects of various stirring and cooling rates indicated that the MSZW increased with increasing and decreasing cooling and stirring rates,respectively.Furthermore,the induction times at various temperatures and supersaturation ratios were also measured.The results indicated that homogeneous nucleation could occur at high supersaturation,whereas heterogeneous nucleation was more likely to occur at low supersaturation.Based on the classical nucleation theory and induction period data,the calculated solid-liquid interfacial tensions of thiourea in deionized water at 302.46 and 312.58 K were 2.86 and 2.94 mJ·m^(-2),respectively.

Solubility and metastable zone width measurement of 2,4-diaminobenzenesulfonic acid in(H_(2)SO_(4)+H_(2)O)system

The equilibrium solubility of 2,4-diaminobenzenesulfonic acid and super solubility as well as metastable zone width were measured in(H_(2)SO_(4)+H_(2)O) system by the laser dynamic method at elevate temperature range from 298.15 K to 338.15 K.2,4-Diaminobenzenesulfonic acid solubility dependence on the temperature and solvent composition were correlated by the modified Apelblat equation,(CNIBS)/Redlich-Kister model and Jouyban-Acree model.The correlated results by three correlation models were in good accord with the experimental values according to relative average deviations(RD),root-mean-square deviations(RMSD),and correlation coefficients(R^(2)).The metastable zone width increased with temperature and sulfuric acid content.The dissolution enthalpy,dissolution entropy and the Gibbs energy were calculated from the experimental values,which indicated that dissolution process of the 2,4-diaminobenzenesulfonic acid was endothermic.The solubility and calculation models of 2,4-diaminobenzenesulfonic acid in(sulfuric acid+water)system could provide the basic data to the crystallization and purifying of the 2,4-diaminobenzenesulfonic acid.

A Kinematic Thermal Model for Descending Slabs with Velocity Boundary Layers:A Case Study for the Tonga Subducting Slab

For the purpose of investigating the influence of metastable olivine（MO） phase transformations on both deep seismicity and stagnation of slabs,we constructed a 2-dimensional finite element thermal model for a 120 Ma-old 50°dipping oceanic lithosphere descending at 10 cm/yr with velocity boundary layers,which would mitigate the interference of constant velocity field for the slab. The resulting temperatures show that most of intermediate and deep earthquakes occurring within the Tonga slab are occurring inside the 800℃and 1200℃isotherm,respectively.The elevation of olivine transformation near～410 km and respective persistence of metastable olivine and spinel within the transition zone and beneath 660 km would thus result in bimodal positive,zonal,negative density anomalies,respectively.These results together with the resulting pressure anomalies may reflect the stress pattern of the Tonga slab：（i） slab pull force exerts above a depth of～230 km;（ii） MO existence changes the buoyancy force within the transition zone and facilitates slab stagnation at a depth of 660 km;（iii） as the subducting materials accumulated over 660 km,deepest earthquakes occur due to MO transformation;（iv） a flattened‘slab’ may penetrate into the lower mantle due to the density increment of Sp transformation.

Insight into the role of ethylene glycol on thermodynamics and nucleation kinetics of dimethyl terephthalate in mixed solvent system

Dissolution and nucleation are two essential processes for industrial crystallization.This paper in-vestigates the effect of ethylene glycol addition on the crystallization behavior of dimethyl terephthalate(DMT)in solution.The DMT solubility in mixed solvent system(methanol-ethylene glycol)was deter-mined by isothermal satiation approach,and the solubility was associated using seven models.The model fitting results were consistent with the experimental values.Based on the results,the metastable zone width(MSZW)of DMT was detected by the polythermal approach;the modified Sangwal's theory was used to investigate the nucleation behavior,which can provide a new way of thought for better analysis of the crystallization behavior.The results demonstrated that MSZW was associated with various elements,such as cooling rate,saturation temperature and mass fraction of ethylene glycol.The addition of ethylene glycol slowed down the nucleation rate as shown by the broadening of MSZW.We derive the solid-liquid interface energy,the nucleation driving force,the critical nucleation size and the critical Gibbs free energy according to the classical nucleation theory.It is demonstrated that the nucleation driving force and the solid-liquid interface energy are dependent and jointly influence the MSZW.

Kinetic study of complicated anti-solvent and cooling crystallization of disodium 5′-ribonucleotide

Disodium 5′-ribonucleotide,which is composed of disodium 5′-inosine(IMP)and disodium 5′-guanosine(GMP),is an important food additive.The lack of kinetic studies of it causes a lack of clarity in understanding the complicated multi-solute crystallization of IMP+GMP in ethanol-water.In this work,process analytical technology tools were used to obtain the thermodynamics and kinetic data from the experiments,the kinetic parameters of anti-solvent and cooling crystallization were investigated.The crystal form of IMP+GMP mixed crystal was determined,which was consistent with the IMP whether crystallized from pure water or ethanol-water.The effects of different anti-solvent addition rates and cooling rates on the metastable zone widths were studied,and the opposite effect on metastable zone width was found.The modified exponential empirical function was developed to correlate nucleation and growth kinetic equations under different conditions.The kinetic data were well fitted with adjusted correlation coefficient(adj-R^(2)>0.7),which is sufficient to provide a valid reference for process design and control.

Effects of a structurally related substance on the crystallization of paracetamol

Paracetamol （PCM） was crystallized from an isopropanol （IPA） solution containing various small amounts of metacetamol as an additive. The effect on the nucleation kinetics was studied by measuring the induction time to nucleation and the metastable zone width using focused beam reflectance measurements （FBRM） and attenuated total reflectance （ATR-UV/Vis） spectroscopy. Both the induction time and the metastable zone width were expressed as functions of the additive concentration. Small amounts ofmetacetamol （1-4 tool-%） were found to cause significant inhibition to the nucleation by extending both the induction time and the metastable zone width. A progressive change in the morphology of the paracetamol crystals from tabular to columnar habit was observed with increasing metacetamol concentration. The solvent also had a significant effect on the size of the paracetamol crystals as smaller crystals were obtained in IPA than in aqueous solution. The dissolution rate of paracetamol was improved by the incorporation of metacetamol with 4 tool-% having the most effect. A supersaturation control （SSC） approach was implemented for the PCM-IPA system with and without metacetamol in an attempt to control and obtain larger metacetamol-doped paraeetamol crystals.