In a eutectic mixture, what happens when camphor and menthol are incorporated into an ointment base?

• A. They dry out and become powdery
• B. They react to form a new compound
• C. They crystallize into larger crystals
• D. They liquefy to form a liquid phase in the base

Answer: (D)

When camphor and menthol are together, they can form a eutectic, which means the two solids melt at a lower temperature than either one alone. In an ointment base, this depressed melting point causes part of the camphor–menthol mixture to liquefy at room or skin temperature, creating a liquid phase within the semi-solid base. This helps with spreading and release of the actives. It isn’t about drying into powder, forming a new chemical compound, or crystallizing into larger crystals—the key effect is the formation of a liquid phase due to the lowered melting point of the eutectic mixture.