CESARESIKISTRI
1600
Vol. 66
were found to b e linear in displacement within a few per cent, except when the heavy phase of system IV was in the cell. Even then the conductance was linear alt,hough the ca, acitance was st,rongly non-linear. We have not establisfed whether this is due to the error in cell design, to extreme electrode polarization effects, or to the intrinsic behavior of the heavy phase. The last possibilities arise because in the bridge the voltage across the cell depends somewhat on the current hhrough the cell. Materials.-A11 operations with these materials were performed with rigorous exclusion of moisture. Reagent grade diethyl ether was used without, further purification. hmmonium chloroferrate was prepared from FeC13 and NHaCl by first drying these materials separately by refluxing with freshly distilled SOClz, then mixing and filtering off the SOCL. Last traces of SOClz were removed by pumping to low4mm. overnight a t room temperature and then for 1 hr. a t GO". The product was cooled in liquid nitrogen while ether was added and then the mixture was allowed t o warm slowly to room tempemture with occasiona.1stirring. It was then stirred for several hours and finally filtered to yield a green 2.3 M solution of NHaFeC1.$and a solid residue consisting mostly of "&I, which had been in twofold excess. If the cooling step is omitted when the ether is added, local hent'ing produces undesirable side reactions. Analyses.-Samples of the ether solutions were taken volumetrically and analyzed for iron either gravimetrically (Fed&) or volumetrically (titration with Hg,(
Some of the solutions were analyzed for chloride gravimetrically. In the 2.3 M stock solution the atom ratio Cl/Fe was found t o be 4.00. In several cases the coexisting liquid phases a t room temperature (23.4 =k 0.2') were analyzed. The chloroferrate molarities found are (light phase/dense phase) : 0.182/--,0.147/0.804,O.lGl/O .817. After considering the details of these experiments it was concluded that the phase equilibrium is slowly attained and that the second determination is the most reliable. This measurement was part of an attempt to determine the coexistencr curve but the miscibility gap is only widened to 0.13/0.96 when the temperature is lowered to -80' and the method employed was not accurate enough to follow such small changes in detail. Stability of Solutions.-The stock solution decomposed slightly during the course of a week, depositing a small amount of XHICl. The properties of a solution derived from the week-old stock solution (Fig. 3, hexagon) were consistent with the main series of measurements (Fig. 3, circles) which were made during the first day after making the stock solution. Some results with a series of solutions prepared and handled in another less satisfactory way also are included in Fig. 3 (squares) to show that the properties of interest here are not largely determined by traces of impurities. Densities.-In the range c < 0.17 M the densities (g,/ml,) a t 23.4" are given by p = 0.710 0.2~.Hence the molality is given by m = c [ l 0.02c]/0.710.The density of a 0.817 AI solution was found to be 0.85 g./ml.
(24) I. M. Kolthoff a n d P. J. Elving, "Treatise on Analytical Chemistry," Vol. 3, Interscience Publishers, New York, N. Y.,1961, Part 11, p. 310.
Acknowledgment.-The author expresses his appreciation to T. Sun for the analyses.
+
+
TRANSPORT SUIMBERS IS PURE FUSED SALTS BY
C E S s R E SINISTRI
Istituto di Chimica Fisica dell' Uniaersitd, Pavia, Ita1y Received January 17, 196%
The significance of cationic and anionic transport numbers of a pure fused salt is discussed, and particularly the importance of the reference system is pointed out. It is shown that in a pure fused salt the transport numbers are arbitrary quantities, which become defined automatically when the reference frame for velocities is fixed.
The significance of transport numbers in pure fused salts and the possibility of direct experimental measurement of them have been discussed for some years. However, very little attention has been given to the formalism of the reference frame, which is an important aspect of the problem. Therefore, it may be worthwhile to reconsider the whole matter from first principles. Definitions.-Let us consider a salt C, A,formed with V+ cationic constituents1 of valency z+ and molar volume concentration c+, and with v- anionic ronstituents of valency z- (z- < 0) and concentration c-. For the electroneutrality of the system, the following equation holds
z+c+
+ x-c-
=
0
(1)
The transport numbers are defined by means of the ratios of the partial electrical flows
