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I am trying to locate the lowest-melting mixture in a system of three nitrate salts: sodium, potassium, and calcium nitrate. I have the relevant ternary phase diagram, but I am unsure exactly about interpreting it because of the "doubled" stoichiometry of the sodium and potassium salts on the plot.

Ternary phase diagram

I posit that along the drawn-in red line, there is a 50/50 molar mixture of Ca(NO3)2 and (KNO3)2. At the zero NaNO3 limit, this would give 0.5 mol Ca(NO3)2 and 1 mol KNO3, so I understand the composition to be 33.3 mole percent Ca(NO3)2 and 66.7 mole percent KNO3. Is my interpretation correct?

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    $\begingroup$ An interesting way to portray the ternary, but really no weirder than some others. Looks like they wanted to focus/normalize on the (NO3). Given that, yes, I think your interpretation is correct. You might wish to look at the KNO3-Ca(NO3)2 binary and confirm your supposition. $\endgroup$
    – Jon Custer
    Commented Mar 23, 2022 at 20:24
  • $\begingroup$ Ha, unfortunately the same source (Phase Diagrams for Ceramists) gives the same double stoichiometry for each of the applicable binary diagrams! I suppose I will go back and follow the original references in that compilation to see how they're plotted there, but that requires me a physical trip back to the library. $\endgroup$
    – Anger Density
    Commented Mar 25, 2022 at 19:00

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