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Abstract  

The phase diagram for the AgNO3−KNO3 system has been determined using differential scanning calorimetry (DSC). Eutectic point has been found at 391 K andX Ag=0.580 mole fraction AgNO3. The DSC curves indicate the existence of an intermermediate compound (AgNO3·KNO3) in the KNO3-rich region of the phase diagram. This compound was identified in the solid phase by X-ray diffraction. The melting and the crystallization processes were followed with the aid of a hot stage microscope, too.

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Abstract  

DSC purity analysis is based on thermodynamic phase diagrams for substances (purity ≥98%) which undergo a melting point. Impurities which have eutectic behaviour with the analyte are determined together. DSC purity analysis obtained from a single melting event of a 1–2 mg sample is, therefore, extremely attractive for the global assessment of eutectic impurities. The main advantages in early development lie in the very small amount of material necessary and the very fast analysis time. However, the DSC purity analysis cannot replace chromatographic methods which deliver specific individual levels of impurities. Furthermore, a complete validation of a DSC purity method is difficult and time consuming. Despite these limitations, DSC is the best support for the development of chromatographic methods, for purity profile and stability assessment during pharmaceutical development. Parameters of purity determination and validation aspects are discussed. Examples of use in pharmaceutical development are given.

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the thermal events rises when approaching to the eutectic point. In this study the thermal effect corresponding to the eutectic reaction was noticeable on DSC curves for all the mixtures examined ( Figs. 4 , 5 , and 6 ). Fig. 5

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faster release of the drug present in the carrier [ 3 ]. The general method of preparing the samples, running through the Differential Scanning Calorimetry (DSC), and interpreting the results to obtain the eutectic point is labor-intensive and

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observed. The DSC measurements indicate a simple eutectic point for the mixture, and this makes the binary mixture suitable for different applications. Comparing the experimental phase diagram and the ideal phase diagram, the system deviation from the ideal

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determined at 444 and 447 °C are small in comparison to the ternary eutectic peak determined at 403 °C. This confirms the close proximity of the ternary eutectic point. The microstructure of the AZS12 sample consists of a large fraction of the ternary

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Abstract  

The phase diagrams of nifedipine-polyethylene glycol (PEG) 4000 and nifedipine-mannitol systems have been determined. Heating experiments on thermodynamically equilibrated co-melts revealed eutectic behaviour for nifedipine-PEG 4000 mixtures, with the composition of the eutectic point between 40 and 45%w/w of nifedipine. These observations were supported by optical and hot stage microscopy. Nifedipine and mannitol were negligibly miscible in the solid-state, behaving as a binary system with monotectic characteristics. Application of phase diagrams to the production of solid dispersions is shown to be rational, since they provide valuable information on the state of the binary systems under preparation.

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Abstract  

The solid—liquid equilibria of the ternary system H2O—Al(NO3)3—Mg(NO3)2 were studied at –30, –20, –10 and 0°C by using a synthetic method which allows to detemine all the characteristic points of isothermal sections. The stable solid phases which appear are respectively: ice, Al(NO3)3·9H2O, Mg(NO3)2·9H2O and Mg(NO3)2·6H2O. Neither double salts nor mixed crystals are observed in the temperature and composition field studied. Polytherm diagram layout show two invariant transformations correspond with an eutectic point and a peritectic point.

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Abstract  

Liquid-liquid structural transitions have been investigated by means of the emanation method in Fe–S, Co–S, Ni–S melts near the eutectic point. Both polythermal and isothermal conditions were used in the experiments. The superheating values were 0–300 ° above the melting temperature. In order to calculate the diffusion coefficient of220Rn in melts a model connecting the emanation level with the diffusion coefficient of radon was employed. Using the diffusion coefficient vs. viscosity relationship /the Stokes-Einstein relation/ the viscosity of melts as a function of the composition and temperature was obtained. Cluster-formation in sulphide melts was estimated theoretically, the particle number in a cluster as a function of the composition was determined, and a correlation was established between viscosity and particle number in clusters vs. composition.

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