Which instrument is typically used to compound suspensions?

• A. Beaker and stir rod
• B. Spatula and mortar
• C. Mortar and pestle
• D. Scale and balance

Answer: (C)

Reducing particle size and achieving a uniform blend is crucial when making suspensions. A mortar and pestle are designed specifically to grind and triturate powders into a fine, homogeneous powder. This size reduction helps the solid distribute more evenly in the liquid vehicle and improves wetting, so the particles don’t settle out too quickly and can remain suspended more effectively.

Beaker and stir rod are great for mixing liquids, but they don’t reliably break down solid particles to a fine, uniform size. Spatula and mortar might help with transferring or rough mixing, but the essential grinding action is provided by the mortar and pestle. Scale and balance are for weighing ingredients, not for mixing or preparing the suspension.