Densities for dilute aqueous solutions of N,N-dimethylethanolamine (DMEA) and N,N-dimethylethanolammonium chloride (DMEAH⁺Cl^–) were measured relative to water at 283.15 K ≤ T ≤ 363.15 K and 0.1 MPa using vibrating tube densimeters. Volumetric heat capacities of the same solutions were measured at 283.15 K ≤ T ≤ 393.15 K and 0.4 MPa using twin fixed-cell, power-compensation, differential-temperature scanning nanocalorimeters. From these measurements, apparent molar volumes, V_ϕ, and heat capacities, C_p,ϕ, were calculated and corrected for speciation to obtain standard partial molar properties V° and C_p^°, for the species DMEA(aq) and DMEAH⁺Cl^–(aq). The experimental values for V° and C_p^°, measured in this work were combined with high temperature values reported by Bulemela and Tremaine (J. Phys. Chem. B2008, 112, 5626–5645) over the range 423.15 to 598.15 K to derive parameters for the semiempirical “density” model that expresses the standard partial molar thermodynamic properties of aqueous species as a function of temperature and solvent density. The fitted parameters were combined with critically evaluated literature values for the standard molar Gibbs energy and enthalpy of reaction at 298.15 K to obtain values for the ionization constant of N,N-dimethylethanolamine from 283.15 to 598.15 K at steam saturation pressure.

中文翻译：

---

N,N-二甲基乙醇胺和 N,N-二甲基乙醇氯化铵水溶液的标准偏摩尔热容量和体积从 283.15 到 393.15 K，电离常数达到 598.15 K

使用振动管密度计在 283.15 K ≤ T ≤ 363.15 K 和 0.1 MPa 下相对于水测量N , N -二甲基乙醇胺 (DMEA) 和N , N -二甲基乙醇胺(DMEAH ⁺ Cl ^– )稀水溶液的密度。在 283.15 K ≤ T ≤ 393.15 K 和 0.4 MPa 条件下，使用双固定电池、功率补偿、差温扫描纳热量计测量了相同溶液的体积热容量。根据这些测量，表观摩尔体积V _ϕ和热容C _{p ,ϕ}, 计算并校正物种形成以获得标准部分摩尔特性V ° 和C _p ^°，对于物种 DMEA(aq) 和 DMEAH ⁺ Cl ^– (aq)。在这项工作中测量的V ° 和C _p ^°的实验值与 Bulemela 和 Tremaine 报告的高温值相结合 ( J. Phys. Chem. B 2008 , 112, 5626–5645) 在 423.15 到 598.15 K 的范围内推导出半经验“密度”模型的参数，该模型将水性物质的标准偏摩尔热力学性质表示为温度和溶剂密度的函数。拟合参数与标准摩尔吉布斯能和 298.15 K 反应焓的批判性评估文献值相结合，以获得蒸汽饱和压力下N，N-二甲基乙醇胺的电离常数值，范围为283.15 至 598.15 K。