This volume contains evaluated data on the solubility of beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide and barium hydroxide in water and in a number of electrolyte and nonelectrolyte solutions in water. The alkaline earth hydroxides can be divided into two groups depending on the hydration of the solid. First, the sparingly soluble anhydrous beryllium, magnesium and calcium hydroxides, whose freshly precipitated solids are poorly crystalline and show decreasing solubility with aging, and whose solubility in water decreases with increasing temperature. Second, the soluble strontium and barium hydroxide octahydrates that form crystalline precipitates which do not show changes in solubility on aging, and whose solubility in water increases with increasing temperature.