Which of the following describes an oleaginous base?

The definition of an oleaginous base is indeed encapsulated in the statement that it is an ingredient used in compounding that does not dissolve in water. Oleaginous bases are typically derived from oils or fats, which are hydrophobic, meaning they repel water. This property makes them suitable for specific formulations, such as ointments and creams, where a water-resistant barrier is desired.

In pharmaceutical compounding, oleaginous bases can be effective in enhancing the stability and absorption of active ingredients while providing emollient properties to the skin. The inability of these bases to dissolve in water allows them to form a protective layer on the skin, making them ideal for topical applications.

Other potential answers do not capture this critical characteristic of oleaginous bases. For instance, the notion of dissolving in water pertains instead to aqueous bases or hydrophilic compounds, while the mention of liquid formulations does not specifically denote the oleaginous nature of the base. Additionally, volatile compounds are more closely related to extraction processes rather than the characteristics of oleaginous bases used in compounding.