Benzene is very volatile and thus rarely used as a clearing agent, but one advantage when it is used is that it evaporates rapidly from paraffin at its melting point, so waxes don't need to be changed on processor. Which statement is true about benzene in clearing?

• A. It is widely used due to safety
• B. It evaporates slowly from paraffin at the melting point
• C. It evaporates rapidly from paraffin at the melting point, reducing the need to change wax
• D. It is used to stain tissues

Answer: (C)

The key idea is how the clearing agent interacts with paraffin and how its volatility affects the embedding process. Clearing agents must be miscible with both alcohol and paraffin, and an agent that evaporates away as the wax is heated helps keep the embedding wax clean and reduces how often you have to change or refresh the wax. Benzene is very volatile, so it tends to evaporate from the paraffin at the wax’s temperature, leaving less solvent behind in the wax. That means you’d need fewer changes of the embedding wax during processing, which is the practical advantage described.

Despite that benefit, benzene is rarely used today because of safety concerns—it is carcinogenic and toxic—so labs prefer safer clearing agents like xylene or its substitutes. It does not stain tissues or confer any staining advantage, and it does not evaporate slowly in this context, so those options don’t fit.