The Freezing Points of Very Dilute Solutions of Electrolytes

Abstract

This communication is an abstract of a thesis submitted by Frank Hovorka in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at the University of Illinois.

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

“…Equations (24) to (27) give the relations between the experimental values of C p,φ (m) and the equilibrium molalities of the various ions present in these solutions, and will allow values of the standard molar heat capacity changes for each reaction i, ri (15) and (16). (47) As mentioned in the Introduction, activity results for R 2 (SO 4 ) 3 (aq) are very limited.…”

“…(47) As mentioned in the Introduction, activity results for R 2 (SO 4 ) 3 (aq) are very limited. (26)(27)(28)(29) Although these experimental results can be analyzed to yield mean activity coefficients of La 2 (SO 4 ) 3 (aq) and Lu 2 (SO 4 ) 3 (aq), they are not extensive enough to yield experimentally based estimates of the activity coefficients for the individual ions. Thus, it is necessary to estimate the ionic activity coefficients.…”

Isopiestic determination of the osmotic coefficients of Lu2(SO4)3(aq) and H2SO4(aq) at the temperatureT= 298.15 K, and review and revision of the thermodynamic properties of Lu2(SO4)3(aq) and Lu2(SO4)3·8H2O(cr)a

“…Unfortunately, only four of the five freezing temperature measurements of Hovorka and Rodebush (4) are sufficiently precise to yield reliable values of f, and these values are limited to the molality range of (0.001 to 0.01) mol·kg −1 . (2) There is a gap in molality between the upper limit of 0.01 mol·kg −1 for the freezing temperature results and the lower limit of 0.12382 mol·kg −1 for the isopiestic results, in which the values of f drop rapidly from 0.455 to 0.312.…”

“…The only results prior to those studies that yield water activities for these solutions are freezing temperature depression studies for La 2 (SO 4 ) 3 (aq) and Nd 2 (SO 4 ) 3 (aq), (3)(4)(5) but only one set of the freezing temperatures (4) for La 2 (SO 4 ) 3 (aq) was determined with sufficient precision for calculation of reliable osmotic coefficients at the freezing temperatures. (2) To convert these osmotic coefficients at the freezing temperature to a constant temperature such as T=298.15 K requires enthalpies of dilution and, for higher accuracy, heat capacities.…”

The Crystallographic Dependence of the OxidationPotential of Solid Copper

“…Each value represents the mean of at least 12 readings taken, in general, at 15-min intervals with an average deviation of 0.04 my as can be seen in Table II which Because of the inherent unreliability of emf measurements at low electrolyte concentrations, highly dilute solutions were not used in this experiment and the Lewis and Randall (18) method of extrapolating a function of E to infinite dilution to obtain the standard potential was not employed. It appeared that the value of the normal potential could be derived most satisfactorily from freezing point depression measurements (19), and relative partial molar heat content values (20) in the manner outlined by Wetmore and Gordon (21). The assumption was made that a function which empirically represented the freezing point data, j = Amx, where x = 0.423 and A = 1.718, could be extended without significant error to include 0.01447M, the lowest concentration.…”