In this paper, the Henry law (Philos. Trans. R. Soc. London 1803, 93, 29), the Turkdogan rule (J. Iron Steel Inst., London 1955, 179, 39, 155), and two extended Turkdogan rules of Wang (Acta Metall. Sin. (Chin. Ed.) 1980, 16, 195; Ber. Bunsen-Ges. 1998, 102, 1045) are presented in a unified way. Similar to the Henry law, which was first noted empirically from the solubility measurements of gases in water, the Turkdogan rule for carbon-saturated Fe-based liquid alloys can be extended to every kind of liquid and solid solutions such as organic mixtures, aqueous and nonaqueous electrolyte and nonelectrolyte solutions, liquid and solid alloys, molten salt mixtures, slags, and nonstoichiometric solid solutions, resulting in two extended Turkdogan rules of Wang. One solution, {B + C + ... + Z}, obeying the Henry law (or the related classically dilute solution model) may mix with many pure component A to form the solutions {A + B + C + ... + Z} following the first extended Turkdogan rule of Wang (or the related partial dilute solution model) or mix with much more nonideal solutions {A1 + A2 + ... + Aq} to form the solutions {A1 + A2 + ... + Aq + B + C + ... + Z} obeying the second extended Turkdogan rule of Wang (or the related dilute-like solution model). This would indicate that the Turkdogan rule and its extended forms are as important as the Henry law for multicomponent systems.