Aliphatic hydrocarbons are classified as which type?

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

Answer: (B)

Clearing is the function being tested. After dehydration, tissues are filled with alcohol, which is not compatible with embedding media like paraffin. Clearing agents are nonpolar hydrocarbon solvents that are immiscible with water but miscible with paraffin, so they replace the alcohol and render the tissue transparent while preparing it for infiltration with embedding medium. Because aliphatic hydrocarbons are nonpolar solvents, they fit this role as clearing agents. They don’t remove water (that’s what dehydrants do), and they aren’t the embedding medium themselves. The idea of a universal solvent is not the primary classification here; the key role of these agents is clearing.