· For mixtures of solids and semisolids, percent weight in weight;
· For solutions or suspensions of solids in liquids, percent weight in volume;
· For solutions of liquids in liquids, percent volume in volume;
· For solutions of gases in liquids, percent weight in volume.
For example, a 1 percent solution is prepared by dissolving 1 g of a solid or semisolid, or 1 mL of a liquid, in sufficient solvent to make 100 mL of the solution.