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8152200 
Journal Article 
The solubility of calcium hydroxide in aqueous salt solutions 
Johnston, J; Grove, C 
1931 
Yes 
Journal of the American Chemical Society
ISSN: 0002-7863
EISSN: 1520-5126 
53 
11 
3976-3991 
English 
1. Calcium hydroxide of a high degree of purity in the form of well defined crystals has been prepared by a diffusion method. The solubility of this calcium hydroxide was measured at 25° in pure water and in solutions of various strengths of sodium chloride, potassium chloride, lithium chloride, cesium chloride, strontium chloride, barium chloride, sodium bromide, potassium bromide, sodium iodide, sodium nitrate, sodium nitrite, sodium chlorate, sodium perchlorate, and sodium acetate. 2. A new type of solubility apparatus in which the solid is held rigidly in place and the solution to be saturated flows over it has been developed and used in this work. 3. The solubility of crystalline calcium hydroxide in pure water at 25° has been found to be 19.76 millimoles per 1000 g. of solvent. 4. The solubility of calcium hydroxide in solutions of neutral salts goes through a maximum unless limited by the solubility of the salt and then decreases to a point which may be less than that of the compound in pure water. 5. The change in the solubility and in the activity coefficient of the hydroxide with change in the ionic strength follows, to a greater or less extent, values calculated by the use of equations of the type suggested by Hückel but employing empirical constants. Agreement of calculated and observed values is usually better in solutions of salts with low activity coefficients than in solutions of those with high coefficients. The constants for each salt which when introduced into the Hückel equation describe the change of the activity coefficient of calcium hydroxide with change of the ionic strength are given. 6. In a series of salts with a common anion, the activity coefficient of the calcium hydroxide is higher in the salt of lower activity coefficient, while in a series of salts with a common cation, the activity coefficient of the calcium hydroxide is higher in the salt with higher activity coefficient. Uni-univalent hydroxides have the higher activity coefficient in solutions of salts with lower activity coefficients in all cases. This unusual behavior is presumably due to the greater specific sensitivity of the bivalent calcium ion to changes in anion. © 1931, American Chemical Society. All rights reserved.