<P> Glass rods can also be used to induce crystallization in a recrystallization procedure, when they are used to scratch the inside surface of a test tube or beaker . </P> <P> They can also break up an emulsion during an extraction . </P> <P> It is recommended that the rod be cleaned after each use to avoid contamination . Glass rods can normally be cleaned simply by placing them in a beaker of clean water and stirring . </P> <P> These are two classic experiments performed using glass rods . </P>

A stirring rod is used to do which of the following