Levigating agents are chosen based on base type: mineral oil is used for hydrocarbon bases and glycerin for water-removable bases.

Levigating agents are chosen based on base type: mineral oil is used for hydrocarbon bases and glycerin for water-removable bases.

• A. Mineral oil for hydrocarbon bases and glycerin for water-removable bases
• B. Water for hydrocarbon bases and ethanol for water-removable bases
• C. Glycerin for hydrocarbon bases and mineral oil for water-removable bases
• D. Propylene glycol for all bases

Answer: (A)

The concept being tested is matching the levigating agent to the base type so it aids grinding without dissolving the base. For hydrocarbon (oil-based) bases, the levigating agent should be immiscible with the base to create a separate phase that helps disperse the solid particles—mineral oil fits this role well. For water-removable (hydrophilic) bases, a water-miscible agent like glycerin blends with the aqueous phase, improving wetting and facilitating incorporation into the base. Therefore, mineral oil for hydrocarbon bases and glycerin for water-removable bases is the best pairing. Water would not wet or disperse hydrocarbons well and would disrupt the base; ethanol isn’t the standard levigating agent for water-removable bases in this context. Glycerin for hydrocarbon bases is inappropriate due to poor immiscibility, and using mineral oil for a water-removable base wouldn’t aid wetting. Propylene glycol is sometimes used, but it isn’t universally appropriate for all bases.

The concept being tested is matching the levigating agent to the base type so it aids grinding without dissolving the base. For hydrocarbon (oil-based) bases, the levigating agent should be immiscible with the base to create a separate phase that helps disperse the solid particles—mineral oil fits this role well. For water-removable (hydrophilic) bases, a water-miscible agent like glycerin blends with the aqueous phase, improving wetting and facilitating incorporation into the base. Therefore, mineral oil for hydrocarbon bases and glycerin for water-removable bases is the best pairing.

Water would not wet or disperse hydrocarbons well and would disrupt the base; ethanol isn’t the standard levigating agent for water-removable bases in this context. Glycerin for hydrocarbon bases is inappropriate due to poor immiscibility, and using mineral oil for a water-removable base wouldn’t aid wetting. Propylene glycol is sometimes used, but it isn’t universally appropriate for all bases.