temperatures. Apart from its immediate importance in 
desalination nelated *situdies >) the datacane bikely to be 
wserul fLomethe tcaliculbation of Change vot free energy tof sea 
water with temperature and for variation of activity coef- 
18 LCaLOINTES) « 
The relative enthalpies of sea salt solutions at 25°C 
G\imand at S0CG (2) have tbeen reported im canlierspubla- 
caittonse he results ait 73°C vare sunmarizedgin this report. 
Measurements at 3°C are in progress and will be presented 
in a subsequent publication. 
Some effort has also been devoted to the development 
of a suitable mathematical expression for the relative 
enthalpies of sea salt solutions. The Debye-Htickel theory 
seems to be a reasonable starting base. Lange (5) has 
shown that the Debye-Htickel theory represents the heat of 
Ghivithtitom data eneasonablymwell ror sl 1) al—=25 62-15 1-3, and 
tAesales sim ethe 20/001 mollal to 0:01 molal range. To extend 
its validity to higher concentration ranges, many other 
approaches have been published which either had to do with 
the problem of finding a more exact expression for the 
coulombic interactions or which tried to include the other 
effects as well. These "extended" theories invariably 
introduced additional empirical parameters. In principle, 
Similar results can be obtained mathematically by adding a 
power series to the expression derived from Debye-Htckel 
thconyes Although taipossibletphysical significance isihost; 
the experimental data can be correlated more easily. One 
such "extended model" has been developed and used in this 
work. 
At stl higher ‘concentrations, even’ the "extended" 
theories fail to correlate (the data satisfactorily. 9 tthe 
Debye-Htickel theory considers only the long range inter- 
actvonsof ons. At Thigher concentrations, “ion solvent 
interactions and short range interactions become far more 
Significant, necessitating the development of an entirely 
Gitte rent model Miperhiaps sof va (cell vorelatticertype structure, 
using the fused salt as the upper limit of concentration. 
Leitzke, Stoughton and Fouss (6) have suggested a weighted 
Contribution Of the two Significant structures in the form: 
IP (UG). 180) 38 (UC cae 12 ((e2)) fb 36 UC) (ay) 
where P(C) is the value of a given property at concen- 
tration C, P(0) is the Debye-Huckel description of that 
property and P(~) represents the concentrated solution 
OS) 
