The interfacial tensions have been measured in the region of three-liquid-phase equilibrium in the system ammonium sulfate + water + ethanol + benzene for various overall compositions at several temperatures from 21 to 46 °C. The three-phase equilibrium terminates in a tricritical point at 49 °C. The variation of the interfacial tensions along either of two different paths of approach to the tricritical temperature , is well described by the power law (T, -T)1•9 **°15. This is in agreement with the ( , -T)2 prediction from theory. The measured variations of the capillary constants and density differences between the phases along these paths are also presented.

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A novel semiorganic nonlinear optical (NLO) crystal, bis(thiourea) barium nitrate (BTBN) was synthesized and grown by slow evaporation method. Structure of the new crystalline compound was confirmed by single crystal X-ray diffraction analysis and it showed that BTBN belongs to orthorhombic crystal system. The crystalline nature of the BTBN was confirmed by powder X-ray diffraction study. Important functional groups of BTBN were identified by FT-IR spectroscopic analysis. UV-Vis-NIR spectral study showed that the grown crystal is transparent in the entire visible region with low cut off wavelength of 304 nm. BTBN exhibits a SHG efficiency which is nearly 2.38 times higher than that of KDP. The BTBN crystal has high mechanical strength and belongs to soft category, which was confirmed by micorhardness study. The thermal stability of BTBN was determined from TGA and DTA thermal study which revealed that the BTBN crystal has thermal stability up to 243.1 °C. The surface properties and presence of elements was analyzed by SEM and EDAX study, respectively.

The Langer-Schwartz model of nucleation and growth has been extended to include the presence of dislocations. The increased nucleation rate of precipitates lying on dislocations, the growth rate of these ellipsoidal precipitates and the effects of heterogeneous site saturation have been included in the model. It is shown that the presence of dislocations can have a large effect on the overall phase separation kinetics at low initial supersaturations, but it is concluded that heterogeneous nucleation cannot account for the observed discrepancies between the Langer-Schwartz theory and previously reported data on the Al-Zn system.