When solubility is expressed in USP terms, which description is generally used?

When solubility is expressed in USP terms, which description is generally used?

• A. g of solute soluble in 1 mL of solvent
• B. g of solute soluble in 100 mL of solvent
• C. mL of solvent required to dissolve 1 g of solute
• D. mL of solvent required to dissolve 100 g of solute

Answer: (C)

In USP terms, solubility is described as the volume of solvent required to dissolve 1 g of solute. This format directly shows how much solvent a fixed amount of solute needs, making it easy to compare solubilities. For example, if 3 mL of solvent is needed to dissolve 1 g, the solubility is 3 mL per gram. The smaller this value, the more soluble the substance; larger values mean lower solubility. While other systems express solubility as grams of solute per a set volume of solvent (like per 100 mL), that isn’t the USP convention. Temperature is usually specified because solubility changes with temperature.

In USP terms, solubility is described as the volume of solvent required to dissolve 1 g of solute. This format directly shows how much solvent a fixed amount of solute needs, making it easy to compare solubilities. For example, if 3 mL of solvent is needed to dissolve 1 g, the solubility is 3 mL per gram. The smaller this value, the more soluble the substance; larger values mean lower solubility. While other systems express solubility as grams of solute per a set volume of solvent (like per 100 mL), that isn’t the USP convention. Temperature is usually specified because solubility changes with temperature.