Which method is used to create a fine powder from a solid substance in pharmacy?

Trituration is the correct method for creating a fine powder from a solid substance in the pharmacy field. This process involves the mechanical grinding of a solid drug or ingredient using a mortar and pestle or similar tools to achieve a uniform and fine particle size. Trituration is essential for ensuring that the solid is adequately reduced to a fine powder, which can lead to improved dissolution and bioavailability when the medication is prepared for administration.

In contrast, mixing typically refers to combining various ingredients to ensure an even distribution but does not specifically imply the reduction of particle size. Blending is similar to mixing but often pertains to the mixing of powders to achieve a specific homogeneity and is less focused on the size reduction aspect. Filtration, on the other hand, is a process used to separate solids from liquids, not for size reduction of solids. Thus, trituration is the specialized technique primarily used for the purpose of creating fine powders in pharmaceutical applications.