Which chemical is commonly used as a clearing agent in histology?

Xylene is commonly used as a clearing agent in histology due to its effectiveness in removing alcohol from tissue samples during the preparation process for embedding in paraffin. After tissues are fixed in formalin, they are usually dehydrated through a series of alcohol solutions. The subsequent clearing step is crucial, as it prepares the tissue for infiltration by molten paraffin wax, which does not mix with alcohol.

Xylene achieves this by acting as a solvent that displaces the alcohol, making it easier for paraffin to penetrate the tissue sections smoothly. Its low boiling point also allows for easy removal during the embedding process, which is essential for producing high-quality histological slides.

Other substances, such as formalin and paraformaldehyde, are fixatives used to preserve tissue architecture and cellular detail prior to processing, rather than clearing agents. Alcohol is involved in the dehydration process but does not serve as a clearing agent in the sense required for the transition to paraffin embedding.