ISSN:
1572-8927
Keywords:
Lanthanum sulfate
;
magnetic float densimeter
;
sound velocimeter
;
density
;
apparent molal volume
;
adiabatic apparent molal compressibility
;
ion pair
;
electrostriction
;
hydration number
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The apparent molal volumes (φv) and adiabatic compressibilities [φK(S)] of La2(SO4)3 solutions have been determined from density and sound speed data at 25°C. The large positive deviations of φv and φK(S) of La2(SO4)3 from the limiting law have been attributed to the formation of the ion pair LaSO 4 + . The observed values of φv and φK(S) have been used to estimate the change in the apparent molal volume and adiabatic compressibility for the formation of LaSO 4 + from $$\Delta \phi (LaSO_4^ + ) = [\phi (obs.) - \phi (2La^{3 + } ,3SO_4^{2 - } )]/\alpha$$ where ϕ(2La3+, 3SO 4 2− ) is the apparent molal volume or adiabatic compressibility of the free ions, and α is the degree of association. The value of $$\Delta \phi _v^o (LaSO_4^ + ) = \Delta \bar V^o (LaSO_4^ + ) = 22.8 \pm 1cm^3 - mole^{ - 1}$$ and $$\Delta \phi _{K(S)}^o (LaSO_4^ + ) = \Delta \bar K_S^o (LaSO_4^ + ) = 85 \pm 20 \times 10^{ - 4} cm^3 - mole^{ - 1} - bar^{ - 1}$$ at infinite dilution are in reasonable agreement with the values determined from the high-pressure conductance data of Fisher and Davis. The number of hydrated water molecules (ca. 11) associated with the formation of LaSO 4 + determined from the volume and compressibility data are in good agreement.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00655373
