Low-temperature heat capacities of a solid complex Zn(Val)SO4·H2O(s) were measured by a precision automated adiabatic calorimeter over the temperature range between 78 and 373 K. The initial dehydration temperature of the coordination compound was determined to be, TD=327.05 K, by analysis of the heat-capacity curve. The experimental values of molar heat capacities were fitted to a polynomial equation of heat capacities (Cp,m) with the reduced temperatures (x), [x=f (T)], by least square method. The polynomial fitted values of the molar heat capacities and fundamental thermodynamic functions of the complex relative to the standard reference temperature 298.15 K were given with the interval of 5 K.
Enthalpies of dissolution of the [ZnSO4·7H2O(s)+Val(s)] (ΔsolHm,l0) and the Zn(Val)SO4·H2O(s) (ΔsolHm,20) in 100.00 mL of 2 mol dm−3 HCl(aq) at T=298.15 K were determined to be, ΔsolHm,l0=(94.588±0.025) kJ mol−1 and ΔsolHm,20=–(46.118±0.055) kJ mol−1, by means of a homemade isoperibol solution–reaction calorimeter. The standard molar enthalpy of formation of the compound was determined as: ΔfHm0 (Zn(Val)SO4·H2O(s), 298.15 K)=–(1850.97±1.92) kJ mol−1, from the enthalpies of dissolution and other auxiliary thermodynamic data through a Hess thermochemical cycle. Furthermore, the reliability of the Hess thermochemical cycle was verified by comparing UV/Vis spectra and the refractive indexes of solution A (from dissolution of the [ZnSO4·7H2O(s)+Val(s)] mixture in 2 mol dm−3 hydrochloric acid) and solution A’ (from dissolution of the complex Zn(Val)SO4·H2O(s) in 2 mol dm−3 hydrochloric acid).
1 Mahmoud, M., Abdel-Monem, S. and Paul, M., U.S. Pat. US 4 039 681, 1977-08-02, Chem. Abstr. 1977, 87, 15196.
2 Taguchi, S., Inokuchi, M., Nakajima, N., Inomata, M. and Natitoh, Y., WO Pat. 10 178, 1992-06-25, Chem. Abstr. 1992, 117, 258218.
3 Harvey, H. and Ashmed, U. K., U.S. Pat. US 4 830 716, 1989-05-16, Chem. Abstr. 1989, 110, 219070.
4 Zhang, XY Yang, XW Jia, Y Gao, SL 2000 Chin. J. Appl. Chem. 17 850-854.
5 Jiang, HY Ren, DH Xie, HF 1986 Chin. J. Northwest Uni. (Natural Science Edition) 22 1.
6 Tan, ZC Xue, B Lu, SW Meng, SH Yuan, XH Song, YJ 2001 J. Therm. Anal. Cal. 63 297 .
7 X.Wang, S Tan, ZC Di, YY Xu, F Wang, MH Sun, LX Zhang, T 2004 J. Therm. Anal. Cal. 76 335 .
8 Ditmars, DA Ishihara, S Chang, SS Bernstein, G West, ED 1982 J. Res. Natl. Bur. Stand. 87 159.
9 Di, YY Tan, ZC Sun, XH Wang, MH Xu, F Liu, YF Sun, LX Zhang, HT 2004 J. Chem. Thermodyn. 36 79 .
10 Di, YY Tan, ZC Gao, SL Wang, SX 2004 J. Chem. Eng. Data 49 965 .
11 D.Wagman, D Evans, WH Parker, VB Schumm, RH Halow, I Bailey, SM Churney, KL Nuttall, RL 1982 Phys. Chem. Ref. Data 11 (suppl. 2) 38, 140.
12 Hutchens, JO Cole, AG Stout, JW 1963 J. Phys. Chem. 67 1128 .
13 Dean, JA et al. 1991 Lange’s Handbook of Chemistry, 13th Ed. Sci. Press Beijing 1986 Translated by Shang, J. F., Cao, S. J., Xin, W. M. and Wei, J. F..