The rate of solution measures how much time a solvent needs to dissolve a certain substance, while solubility expresses the composition of a saturated solution.
Hence, the rate of solubility is measured in Kg/ units, while solubility is measured in g/(100 mL) of solvent. Solubility may be seen as property of a substance and it is of great help in the process of separation of mixtures.
The majority of solubility data provides information regarding solubility of organic compounds in water. The database that contains values regarding solubility of substances in non-aqueous solvents is under construction, still.