Note 3 — Chapter XIII · POTASSIUM, RUBIDIUM, CÆSIUM, AND LITHIUM. SPECTRUM ANALYSIS
George Kamensky translation
The method of separating sodium chloride from potassium chloride has been described in Chapter I. On evaporation of a mixture of the saturated solutions, sodium chloride separates; and then, on cooling, potassium chloride separates, owing to the difference of rate of variation of their solubilities with the temperature. The following are the most trustworthy figures for the solubility of potassium chloride in one hundred parts of water (for sodium chloride, see Chapter X., Note 13):—
10° 20° 40° 60° 100°
32 35 40 46 57
When mixed with solutions of other salts the solubility of potassium chloride naturally varies, but not to any great extent.