Circumstances affecting the solubility of a solid. The solubility of a solid in a liquid depends upon several factors.
1. Nature of the solid. Other conditions being the same, solids vary greatly in their solubility in liquids. This is illustrated in the following table:
Table of Solubility of Solids at 18°
| 100 cc. of water will dissolve: | |
| Calcium chloride | 71.0 g. |
| Sodium chloride | 35.9 |
| Potassium nitrate | 29.1 |
| Copper sulphate | 21.4 |
| Calcium sulphate | 0.207 |
No solids are absolutely insoluble, but the amount dissolved may be so small as to be of no significance for most purposes. Thus barium sulphate, one of the most insoluble of common substances, dissolves in water to the extent of 1 part in 400,000.
2. Nature of the solvent. Liquids vary much in their power to dissolve solids. Some are said to be good solvents, since they dissolve a great variety of substances and considerable quantities of them. Others have small solvent power, dissolving few substances, and those to a slight extent only. Broadly speaking, water is the most general solvent, and alcohol is perhaps second in solvent power.
3. Temperature. The weight of a solid which a given liquid can dissolve varies with the temperature. Usually it increases rapidly as the temperature rises, so that the boiling liquid dissolves several times the weight which the cold liquid will dissolve. In some instances, as in the case of common salt dissolved in water, the temperature has little influence upon the solubility, and a few solids are more soluble in cold water than in hot. The following examples will serve as illustrations: