Apparent molar heat capacities and apparent molar volumes ofY2(SO4)3(aq),La2(SO4)3(aq),Pr2(SO4)3(aq),Nd2(SO4)3(aq),Eu2(SO4)3(aq),Dy2(SO4)3(aq),Ho2(SO4)3(aq), andLu2(SO4)3(aq)atT =  298.15 K andp =  0.1 MPa

✍ Scribed by Robert A. Marriott; ; Andrew W. Hakin; ; Joseph A. Rard

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 526 KB
• Volume: 33
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.2000.0792

✦ Synopsis

The apparent molar heat capacities C • p,φ and apparent molar volumes V • φ of Y 2 (SO 4 ) 3 (aq), La 2 (SO 4 ) 3 (aq), Pr 2 (SO 4 ) 3 (aq), Nd 2 (SO 4 ) 3 (aq), Eu 2 (SO 4 ) 3 (aq), Dy 2 (SO 4 ) 3 (aq), Ho 2 (SO 4 ) 3 (aq), and Lu 2 (SO 4 ) 3 (aq) were measured at T = 298.15 K and p = 0.1 MPa with a Sodev (Picker) flow microcalorimeter and a Sodev vibratingtube densimeter, respectively. These measurements extend from lower molalities of m = (0.005 to 0.018) mol• kg -1 to m = (0.025 to 0.434) mol•kg -1 , where the upper molality limits are slightly below those of the saturated solutions. There are no previously published apparent molar heat capacities for these systems, and only limited apparent molar volume information. Considerable amounts of the RSO + 4 (aq) and R(SO 4 ) - 2 (aq) complexes are present, where R denotes a rare-earth, which complicates the interpretation of these thermodynamic quantities. Values of the ionic molar heat capacities and ionic molar volumes of these complexes at infinite dilution are derived from the experimental information, but the calculations are necessarily quite approximate because of the need to estimate ionic activity coefficients and other thermodynamic quantities. Nevertheless, the derived standard ionic molar properties for the various RSO + 4 (aq) and R(SO 4 ) - 2 (aq) complexes are probably realistic approximations to the actual values. Comparisons indicate that V • φ {RSO + 4 , aq, 298.15 K} = -(6 ± 4) cm 3

• mol -1 and V • φ {R(SO 4 ) - 2 , aq, 298.15 K} = (35 ± 3) cm 3

• mol -1 , with no significant variation