Solubility of Common Calcium Salts

Most calcium salts are almost insoluble in water, or have very low solubility. Only some inorganic and organic calcium salts have relatively high solubility in water. In water treatment, we often utilize the insolubility of inorganic calcium to remove phosphorus. In water-soluble fertilizers, we often utilize the solubility of calcium to increase the absorption of aluminum by crops from ionic calcium. Water-soluble organic ionic calcium can be used to produce compound fertilizers with high phosphorus and high calcium content. Potassium phosphite can be compounded with some organic ionic calcium without precipitation. Therefore, the solubility of calcium is of great significance in different chemical synthesis processes. What are the characteristics and patterns of the solubility of different calcium salts? What are the differences in solubility between organic and inorganic calcium? Below, we will explain the solubility of common calcium salts in detail.

1. Soluble calcium salts (at room temperature 20-30℃, 100ml purified water, unit: g)

Calcium chloride: 74.5

Calcium hypophosphite: 16.7

Calcium hydrogen phosphite: 5

Calcium nitrate: 129

Calcium bromide: 143

Calcium iodide: 209

Calcium bicarbonate: 1.66

Calcium dihydrogen phosphate: 1.8

Calcium hydrogen maate: 8.5 (45℃); 32 (57℃)

2. Insoluble or poorly soluble calcium salts (at room temperature 20-30℃, 100ml purified water, unit: g)

Calcium sulfate: 0.29

Calcium phosphite: sparingly soluble

Calcium phosphate: 0.002

Calcium citrate: 0.08

Calcium maate: 0.8

Calcium tartrate: 0.02

Calcium oxalate: insoluble

Tricalcium phosphate: insoluble

Generally speaking, the solubility of common calcium salts follows certain patterns. Generally, water-soluble calcium salts contain hydrophilic ions such as chloride, bromine, and nitrate, while insoluble or poorly soluble calcium salts contain weakly hydrophilic ions such as phosphate, sulfate, and carbonate. The lower the pH and the stronger the acidity, the higher the solubility of calcium salts. Higher temperatures also increase solubility. Alkaline environments and low temperatures lead to decreased solubility. The dissolution process is generally exothermic, with a greater tendency for spontaneous reaction, making calcium salts readily soluble in water. Conversely, the dissolution process is generally endothermic, requiring the absorption of heat from the environment, with a less spontaneous tendency for spontaneous reaction, making calcium salts less soluble.