Toluene is classified as which type?

• A. Dehydrant
• B. Clearing
• C. Infiltration/embedding
• D. Dehydrant and clearing aka universal solvent

Answer: (B)

Toluene is classified as a clearing agent. In tissue processing, after dehydration, a clearing agent replaces the dehydrant (usually alcohol) and makes the tissue transparent while also being miscible with paraffin to allow infiltration. Toluene fits this role because it bridges ethanol and paraffin, preparing the tissue for embedding. It is not a dehydrant, since it does not remove water, and it is not used for infiltration/embedding by itself. While some sources may refer to clearing agents as universal solvents, the primary histology use of toluene is as a clearing agent.