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Thermoelastic surface properties of seawater in coastal areas of the Baltic Sea

Boniewicz-Szmyt K., Pogorzelski S. J.

Oceanologia

2016

No. 58 (1)

25--38

Correlations and data for the thermoelastic surface properties of seawater were determined by means of surface tension-temperature and surface pressure-area isotherm measurements performed in Baltic Sea coastal waters (Gulf of Gdańsk, Poland). Thermodynamic surface parameters examined include: surface free energy-γ, entropy, enthalpy, surface specific heat of air-seawater (AW), air-crude oil (AO) and crude oil-seawater (OW) interfaces, and the surface elasticity was quantified in terms of complex viscoelasticity modules with relaxation times of the transition processes. The spatial and temporal evolution of the parameters differed significantly from the literature data for seawater since the effect of surface active substances of natural and municipal origin was likely to be present in these coastal waters. The seawater surface turned out to have the viscoelastic 2D character as well as other interfacial systems AO and OW where three crude oils in contact with the seawater were studied for comparison. The dilational elasticity modules were found to follow the sequence EAW > EOW > EAO. Composite oil lens-covered seawater exhibited a significant drop of E from EAW (crude oil free surface) even for low oil coverage fraction F0. The obtained surface and interfacial tension-temperature dependences allowed to correct the spreading coefficient (S = γAW − γAO − γOW) to the desired temperature range, for example. The latter parameter with the sea surface elasticity data allows one to test the modified model of crude oil spreading proposed by the authors (Boniewicz-Szmyt and Pogorzelski, 2008), for spreading kinetics phenomenon at the surface-tension regime.

Solubility of a pharmacological intermediate drug Isatin in different solvents at various temperatures

Baluja S., Bhalodia R., Bhatt M., Vekariya N., Gajera R.

International Letters of Chemistry, Physics and Astronomy

2013

Vol. 12

36--46

The solubility of isatin in different solvents was studied by a gravimetrical method from (298.15 to 318.15) K under atmospheric pressure and the solubility data were correlated against temperature. The solvents selected for the present study are: water, methanol, ethanol, 1-butanol, dichloromethane, dichloroethane, chloroform and carbon tetra chloride. Among chlorinated solvents, solubility is observed to be maximum in 1, 2-dichloroethane and minimum in dichloromethane whereas in alcohols, maximum solubility is observed in methanol. In water, solubility is found to be minimum. Further, some thermodynamic parameters such as Gibb’s energy (ΔGsol), heat of solution (ΔHsol) and entropy of solution (ΔSsol) have also been evaluated.