Aqueous Salt Solutions

 

The NaCl-K2SO4-H2O reciprocal salt system

In the quaternary (Na+,K+)-(Cl-,SO42-)-H2O system at 100°C, the following solid phases appear:

The phase diagram below shows the concentration ranges in which the various solid phases appear. The concentration unit is charge fraction, which corresponds to equivalent fraction. The water contents of the saturated solutions are indicated by the numbers given at the grid intersections as mass percent water.

Janecke diagram for the NaCl - K2SO4 - H2O reciprocal salt system at 100°C

Each corner of the phase diagram represents a binary solution, and each of the four sides a ternary solution. The lower left corner of the figure to the right represents a KCl solution, the lower right corner a K2SO4 solution. Correspondingly, the upper corners represent a NaCl and a Na2SO4 solution.

A contour chart of the same system is shown below to the left. This diagram does not show the phase diagram lines, but only the water content in each part of the diagram. The water content is indicated by colors as shown in the legend, where the numbers are mass% water. The brown color indicates a high water content and the dark blue a low water content.

Below to the right is a 3-D plot of the same diagram. It uses the same color scheme as the contour plot to indicate the water level. The phase diagram lines can be seen in the 3-D plot as the lines corresponds to the "valleys" in the 3-D plot. The low water content at the phase diagram lines is indicative of the common tendency of salting in.

Contour plot for the reciprocal salt system NaCl - K2SO4 - H2O 3D plot of the reciprocal salt system NaCl - K2SO4 - H2O at 100°C