Rosenstiel School of Marine and Atmospheric Chemistry, University of Miami, Miami, Florida 33149, USA.
J Phys Chem B. 2010 Dec 16;114(49):16099-104. doi: 10.1021/jp101766v. Epub 2010 Jul 27.
The apparent molal volume V(ϕ) and adiabatic compressibility κ(ϕ) of H(3)PO(4), NaH(2)PO(4), Na(2)HPO(4), and Na(3)PO(4) have been determined from density and sound speed measurements in 0.725 m NaCl solutions at 25 °C. The partial molal volumes V(i)* and compressibilities κ(i)* have been determined by extrapolating the values of V(ϕ) and κ(ϕ) to infinite dilution in the NaCl media. The results have been compared to earlier measurements made on a number of electrolytes in NaCl media. The phosphate results showed correlations between the values of V(i)* and κ(i)* as found for other electrolytes. The values for the volume ΔV(i) and compressibility Δκ(i) changes for the dissociation of H(3)PO(4) in 0.725 m NaCl have been calculated from the measurements. The calculated values of ΔV(i) and compressibility Δκ(i) have been used to estimate the effect of pressure K(P)/K(0) on the dissociation of H(3)PO(4) in the oceans using RT ln[K(P)/K(0)] = -ΔV(i)P + 0.5Δκ(i)P(2), where P is the applied pressure in bars. The results are in reasonable agreement with directly measured values.
在 25°C 下，通过在 0.725 m NaCl 溶液中测量密度和声速，确定了 H(3)PO(4)、NaH(2)PO(4)、Na(2)HPO(4)和 Na(3)PO(4)的表观偏摩尔体积 V(ϕ)和绝热压缩率 κ(ϕ)。通过将 V(ϕ)和 κ(ϕ)的值外推至 NaCl 介质中的无限稀释，确定了偏摩尔体积 V(i)*和压缩率 κ(i)*的值。将这些结果与在 NaCl 介质中对许多电解质进行的早期测量进行了比较。磷酸盐的结果表明，与其他电解质一样，V(i)*和 κ(i)*的值之间存在相关性。根据测量结果，计算了 H(3)PO(4)在 0.725 m NaCl 中离解的体积变化 ΔV(i)和压缩率变化 Δκ(i)的值。使用 RT ln[K(P)/K(0)] = -ΔV(i)P + 0.5Δκ(i)P(2)，其中 P 是以巴为单位的施加压力，计算了压力 K(P)/K(0)对海洋中 H(3)PO(4)离解的影响，从而估算了计算出的 ΔV(i)和压缩率 Δκ(i)值。结果与直接测量值相当吻合。
