Thermodynamic data of the NZP compounds family

Summary The thermodynamic data for NZP compounds MZr₂(PO₄)₃ (M=Na, K, Rb, Cs, Zr_0.25) and Na₅D(PO₄)₃ (D=Ti, Zr) are reported. The heat capacities of the phosphates were measured between T=7 and T=640 K. The standard enthalpies entropies, and Gibbs functions of formation at T=298.15 K were derived. The obtained thermodynamic characteristics of phosphates of the NZP type structure and literature data are summarized. Thermodynamic functions of reactions of solid-state synthesis were calculated and the usability of ceramic technology for obtaining NZP compounds was proved.     

量热法测定氯化钐与甘氨酸配合物的标准生成焓

稀土在生命科学领域的研究日益受到人们关注,稀土化合物所具有的抑菌、抑癌、消炎等作用及其作用机理的探讨已有报道［１～３］。最近几年稀土在生物领域中的研究又有了新的突破和进展,从稀土与氨基酸、蛋白质、膜脂及膜蛋白的作用到其对ＤＮＡ。ＲＮＡ的影响［１,４］,从稀土的分子水平、细胞及亚细胞水平到动物整体实验的系统研究［５,６］等,分别从不同的层次、不同的水平研究了稀土的生物效应。但至目前为止,稀土的生物效应机理及其对人体的影响尚未得到令人满意的解释。由于氨基酸是构成人体蛋白质的基本单位,故研究稀土与氨基…     

Conductometric and DSC evidence for a high temperature phase transition in cobalt dibromide

A solid-state phase transition in cobalt dibromide at 647 K has been revealed by three different alternative current techniques. A small thermal effect of (181±18) J mol⁻¹ corresponding to the enthalpy of the transition has been determined by differential scanning calorimetry. The effect was observed on cooling and on heating as well.     

The molar formation enthalpy of nano-SiO<Subscript>2</Subscript> with different surface area

Three samples of silicon dioxide were syhthesized and their surface areas were measured. A thermo-chemical cycle was designed to calculate the molar formation enthalpy. The molar formation enthalpy, Δ_f H _m^Φ, for three amorphous silica with the Langmuir surface area 198.0854, 25.1108 and 11.9821 m² g⁻¹ gave −895.52, −910.86 and −915.67 kJ mol⁻¹, respectively. With the increasing surface area, the values of Δ_f H _m^Φ increased accordingly. The results suggest that the silica with larger surface area is more unstable. The wetting heat was also measured by adding the silica powder into water. With the rehydration of the more SiOH groups on the surface, the larger surface areas of silica lead to the more wetting heat. A smaller particle has the more unstable hydroxyl groups and surface energy.     

Excess molar enthalpies of binary mixtures containing poly(ethylene glycol) 200+four cyclic ethers at (288.15, 298.15 and 313.15) K and at atmospheric pressure

Excess molar enthalpies, H_m^E, of binary mixtures containing poly(ethylene glycol) (PEG) 200+1,3-dioxolane, PEG 200+1,4-dioxane, PEG 200+oxolane and PEG 200+oxane were determined using a flow microcalorimeter at (288.15, 298.15 and 313.15) K and at atmospheric pressure. The H_m^E curves are always positive, with maxima varying from 393 J mol⁻¹ (1,3-dioxolane) to 658 J mol⁻¹ (oxolane), showing asymmetrical trends. The effect of the temperature is well marked on the calorimetric data that increase as the temperature is increased. The Redlich-Kister polynomial was used to estimate the binary fitting parameters. Root-mean-square deviations from the regression lines are reported.     

Excess enthalpies of binary solvent mixtures of N,N-dimethylacetamide with aliphatic alcohols

The excess enthalpies H _m ^E of binary solvent mixtures of N,N-dimethylacetamide with methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and t-butanol have been measured with a flow microcalorimeter at 40°C. The excess enthalpies increase as the length of the alkyl chain of the primary alcohol increases. The values for methanol are negative, those for ethanol change sign, and those for 1-propanol, and more clearly those for 1-butanol, are positive. The mixtures of the secondary and the tertiary alcohol exhibit mainly positive values of H _m ^E . Solute-solute and solute-solvent interactions in these mixtures are discussed on the basis of the results.     

高氯酸钆与脯氨酸形成配合物的反应热化学研究

稀土氨基酸配合物具有许多特殊的性能,1975年Anghileri等报到了氯化镧与甘氨酸的配合物具有抗肿瘤作用^[1],此后人们又陆续发现这类配合物在医药,防腐剂,动物饲料,农用微肥,钙离子探针,羊毛染色等方面具有广泛的实用价值[2,3],因而引起人们对研究稀土氨基酸配合物的兴趣。但目前这类配合物的制备和性质报道较多^[4,5],基础热化学的研究尚待展开^[6]。     

A solution-reaction isoperibol calorimeter and standard molar enthalpies of formation of Ln(hq)2Ac (Ln = La, Pr)

An on-line solution-reaction isoperibol calorimeter has been constructed. The performance of the apparatus was evaluated by measuring the molar enthalpy of solution of KCl in water at 298.15 K. The uncertainty and the inaccurary of the experimental results were within ±0.3% compared with the recommended reference data. Using the calorimeter, the molar enthalpies of reaction for the following two reactions: LaCl₃·7H₂O(s)+2Hhq(s)+NaAc(s)=La(hq)₂Ac(s)+NaCl(s)+2HCl(g)+7H₂O(l) and PrCl₃·6H₂O(s)+2Hhq(s)+NaAc(s)=Pr(hq)₂Ac(s)+NaCl(s)+2HCl(g)+6H₂O(l), were determined at T=298.15 K, as −(78.3±0.6) and −(97.3±0.5) kJ mol^−l, respectively. From the above molar enthalpies of reaction and other auxiliary thermodynamic quantities, the standard molar enthalpies of formation of La(hq)₂Ac and Pr(hq)₂Ac, at T=298.15 K, have been derived to be −(1535.5±0.7) and −(1536.7±0.6) kJ mol^−l, respectively.