CHEMISTRY: HARKINS, HALL, AND ROBERTS 
643 
temperature readings to 0.00005°, the work was carried out by the 
freezing-point method. 
Freezing-point determinations at various concentrations were made 
upon solutions of mannite, erythrite, potassium iodate, sodium iodate, 
magnesium sulphate, potassium sulphate, barium chloride, and cobalt 
chloride, and upon mixtures of potassium chloride and potassium ni- 
trate, potassium chloride and mannite, potassium and sodium sulphates, 
and of potassium and sodium iodates. The method used was similar 
to that of Adams, and the same apparatus was used. Most of the anal- 
yses for the determination of the concentration of the solutions, were 
made by the use of a Haber-Rayleigh-Zeiss water-interferometer. 
The results are expressed most clearly in the form of curves, which 
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1 2 5 10 20 50 100 200 500 
FIG. 1 
are presented in figures 1-3. These figures show the values of the 
freezing-point lowerings divided by the equivalent concentrations 
(AT/N) on the Y-axis, and the logarithms of the concentrations in milli- 
equivalents per liter on the X-axis. Figure 1 gives the set of curves for 
potassium nitrate, potassium chloride, and their equimolal mixture. 
The curve for the mixture will be seen to lie about half-way between 
those which represent the salts separately. Figure 2 gives the results 
for sodium iodate, a uni-univalent salt, and for magnesium sulphate, a 
bi-bivalent salt. Potassium iodate, and an equimolal mixture of it 
with sodium iodate were also studied, but the two curves are not given 
as they are almost coincident with that for sodium iodate. Figure 3 
gives those for potassium sulphate, barium chloride, and cobaltous 
