ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Preparation and Thermal Chemical Properties of Compounds of Zinc Nitrate with Valine

S. Gao, S. Chen, X. Yang, and Q. Shi

Department of Chemistry, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Northwest University, Xi’an, 710069, P. R. China

E-mail: gaoshli@nwu.edu.cn

Received: 12 August 2002

Abstract: The solubility property of the Zn(NO3)2—Val—H2O system at 25°C in the whole composition range has been investigated by the semimicrophase equilibrium method. The corresponding phase diagrams and refractive index diagrams were constructed. From the phase equilibrium results, the incongruently soluble compounds Zn(Val)(NO₃)₂ ·2H₂O, Zn(Val)₂(NO₃)₂ ·H₂O, and Zn(Val)₃(NO₃)₂·H₂O were synthesized and characterized by IR, XRD, TG—DTG, as well as chemical and elemental analyses. The constant-volume combustion energies of the compounds, Δ_cE, determined by a precision rotating bomb calorimeter at 298.15 K, were (−10064.24 ± 5.41) J g⁻¹, (−13523.98 ± 7.54) J g⁻¹, and (−16116.13 ± 7.58) J g⁻¹, respectively. The standard enthalpies of combustion for these compounds, Δ_cH, were calculated to be (−3442.21 ± 2.25) kJ mol ⁻¹, (−5971.2 ± 3.32) kJ mol⁻¹, and (−9007.26 ± 4.24) kJ mol⁻¹ while the standard enthalpies of formation were (−1017.34± 2.00) kJ mol⁻¹, (−1742.93 ± 3.61) kJ mol⁻¹, and (−2245.70 ± 4.73) kJ mol⁻¹. The enthalpies of solution in condition of simulating human gastric juice (37°C, pH = 1, the solution of hydrochloric acid), which were also measured by a microcalorimeter, were (22.17 ± 0.05) kJ mol⁻¹, (14.89 ± 0.04) kJ mol⁻¹, and (6.85 ± 0.07) kJ mol⁻¹, respectively.

Full paper in Portable Document Format: 582a87.pdf

Chemical Papers 58 (2) 87–92 (2004)