Ballerat-Busserolles Karine, Sedlbauer Josef, Majer Vladimir
Laboratoire de Thermodynamique des Solutions et des Polymères, Université Blaise Pascal Clermont-Ferrand/CNRS, 63177 Aubière, France.
J Phys Chem B. 2007 Jan 11;111(1):181-90. doi: 10.1021/jp064650m.
The densities and heat capacities of solutions of phosphoric acid, 0.05 to 1 mol kg-1, were measured using flow vibrating tube densitometry and differential Picker-type calorimetry at temperatures up to 623 K and at pressures up to 28 MPa. The standard molar volumes and heat capacities of molecular H3PO4(aq) were obtained, via the apparent molar properties corrected for partial dissociation, by extrapolation to infinite dilution. The data on standard derivative properties were correlated simultaneously with the dissociation constants of phosphoric acid from the literature using the theoretically founded SOCW model. This made it possible to describe the standard thermodynamic properties, particularly the standard chemical potential, of both molecular and ionized phosphoric acid at temperatures up to at least 623 K and at pressures up to 200 MPa. This representation allows one to easily calculate the first-degree dissociation constant of H3PO4(aq). The performance of the SOCW model was compared with the other approaches for calculating the high-temperature dissociation constant of the phosphoric acid. Using the standard derivative properties, sensitively reflecting the interactions between the solute and the solvent, the high-temperature behavior of H3PO4(aq) is compared with that of other weak acids.
使用流动振动管密度计和微分Picker型量热法，在温度高达623 K和压力高达28 MPa的条件下，测量了浓度为0.05至1 mol kg⁻¹的磷酸溶液的密度和热容。通过对部分解离校正后的表观摩尔性质外推至无限稀释，获得了分子H₃PO₄(aq)的标准摩尔体积和热容。利用理论上建立的SOCW模型，将标准导数性质的数据与文献中磷酸的解离常数同时进行关联。这使得能够描述分子态和离子态磷酸在温度至少高达623 K和压力高达200 MPa时的标准热力学性质，特别是标准化学势。这种表示方式使得人们能够轻松计算H₃PO₄(aq)的一级解离常数。将SOCW模型的性能与计算磷酸高温解离常数的其他方法进行了比较。利用能灵敏反映溶质与溶剂之间相互作用的标准导数性质，将H₃PO₄(aq)的高温行为与其他弱酸的高温行为进行了比较。
