1070-4272/01/7411-1793$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 11, 2001, pp. 1793!1796. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 11,
2001, pp. 1741!1744.
Original Russian Text Copyright + 2001 by Morachevskii, Bykova.
OF SYSTEMS AND PROCESSES
Thermodynamic Analysis of Component Interaction
in Liquid Alloys of the Potassium!Indium System
A. G. Morachevskii and M. A. Bykova
St. Petersburg State Technical University, St. Petersburg, Russia
Received July 10, 2001
Abstract- The thermodynamic properties of K3In liquid alloys were compared and discussed. The alternat-
ing positive and negative deviations from the ideal behavior were observed in the system.
Markedly different data are presented in the litera-
ture on the phase diagram of the potassium3indium
system . According to Thummel and Klemm ,
potassium and indium form the congruently melting
(mp 745 K) and incongruently melt-
ing compound KIn
, with the peritectic horizontal
lying at 698 K. In the composition range 503
90 mol % potassium the liquidus line is nearly hori-
zontal, i.e., a tendency to separation is probable. Ac-
cording to Yatsenko et al. , the system has the
phase separation region, and the compound K
melts congruently at 753 K and has a very narrow
homogeneity region. The composition KIn
ported in that work for the incongruently melting
compound. The presence of the homogeneity region
in the system was confirmed by differential thermal
 and magnetochemical  analyses and by elec-
trical resistance measurements . However, data on
the upper critical temperature differ essentially. Bush-
manov  reported 731 K, whereas Melekhov ,
818 K. In Yatsenko’s monograph , the immiscibil-
ity region is presented according to . According to
the later data [8, 9], the incongruently melting com-
pound has the composition K
melting point is 751+6 K, and the upper critical tem-
perature of separation does not exceed this value.
Thermodynamic properties of liquid K3In alloys
were studied for the first time by the emf method
using potassium glass (3.8 wt % K
O) as solid cation-
conducting electrolyte (0.016 < x
< 0.815, 15 com-
positions, 7203810 K) . It was found that the
activity isotherm of potassium at 750 K has alternat-
ing deviations from the ideal behavior, and the corre-
sponding curve for indium is located in the region
of negative deviations from Raoult’s law (Fig. 1).
The integral molar excess Gibbs energy DG
tive over the entire composition range (Fig. 2), with
the curve extremum lying in the region of formation
of intermetallic compounds.
More recently, Dergacheva et al.  studied,
also by the emf method, the thermodynamic properties
Fig. 1. Potassium activity a
in K3In liquid alloys. (x
tassium mole fraction; the same for Figs. 234. Reference,
T (K): (1) , 750; (2) , 753; and (3) , 773; the
same for Fig. 2.
Fig. 2. Integral molar excess Gibbs energy DG
position in the K3In system.