Papers by Keyword: Solubility Product

Abstract: In this paper, the theophylline(TP)-nicotinamide(NCT) cocrystal was chosenas an example for studying the preparation analysis-identification and thermodynamic analysis of cocrystal systems. TP-NCT cocrystal was prepared by the methods of grinding, gringding, slurry and evaporation crystallization respectively. The dependence of the cocrystal solubility on the concentration of cocrystal components in solution were measured and correlatedby cocrystal solubility product. The results indicatethatTP and NCT do not ionize or form complexes in ethanol, and with the temperature increasing, both the solubility of theTP-NCTcocrystal and the solubility product increase.Finally, the ternary phasediagrams for the system of TP-NCT-ethanol at (298.15 and 308.15) K, which can provide the theoretical basis forcrystallization processes, are presented.

Abstract: In this paper, firstly, the equilibrium solubility product formula of MoC with NaCl type cubic crystal structure in ferrite has been deduced by thermodynamic method, according to the free energy change of molybdenum and carbon dissolved in ferrite and the formation energy of MoC. On the basis of deducing activity coefficients of Mo in iron, the solubility product formula of MoC in austenite has been obtained according to the relationship of solubility product of MoC in austenite and ferrite. Finally, the solubility products for MoC and NbC in iron are compared. The solubility product formulae of MoC deduced would play an important role in related theoretical research and practical production.

Abstract: An electrochemical sensor based on the silver sulphide precipitate was fabricated in the laboratory and characterized by x-ray diffraction, SEM equipped with EDAX, and electrochemical techniques. Ion selective electrode (ISE) was found to be sensitive enough to sense the sulphide ion concentration from 10-1 to 10-5 M in alkaline medium. The change in electrode potential per decade change in sulphide ion concentration was found to be 31.5 mV at laboratory temperature indicating adherence of the ion selective electrode to Nernst’s equation. The sensor have been successfully used for the quantitative determination of thiamine in pharmaceutical preparations, hydrogen sulphide in cigarette smoke and determination of solubility products of sparingly soluble silver salts. A trace amount of hydrogen sulphide, a toxic gas, is present in the cigarette smoke. The quantitative estimation of hydrogen sulphide in cigarette smoke is a challenging task to analytical chemist. Hydrogen sulphide in cigarette smoke had been determined by absorbing the cigarette smoke in 0.1 M sodium hydroxide and the resulting solution was analyzed using silver sulphide based ion sensor by standard addition technique using modified Gran plot. The average amounts of hydrogen sulphide produced by a stick of cigarette in 8 different brands of Nepalese cigarette ware found to range from 0.0332 mg to 0.0766 mg. The sensitivity and reliability of these home made ion sensors were excellent and in par with commercial electrodes. For developing countries like Nepal, who can not afford to procure high cost commercial ion selective electrodes, these home made ion sensors are especially appealing since the sensor can be fabricated with ease from the materials that are readily available in the chemistry laboratory and the sensor is quite sensitive and gives reproducible results which are sufficiently accurate for the analysis with ion selective electrodes.