Which dehydrating agent is used for urgent biopsies within 2 hours?

Acetone is the correct choice for a dehydrating agent used for urgent biopsies within a time frame of 2 hours. It is a highly effective solvent that can rapidly dehydrate tissues, making it particularly useful in situations where quick processing is essential, such as for urgent biopsies.

Acetone's ability to dissolve organic materials quickly aids in swift tissue preparation, allowing for faster embedding and sectioning, which is vital in urgent clinical settings where results are needed promptly. Its low boiling point also facilitates rapid evaporation, which contributes to efficient dehydration without damaging the tissue structure.

In contrast, while other agents like alcohol and dioxane can also serve as dehydrating agents, they typically require longer periods for effective tissue processing. Alcohol is commonly used but usually necessitates a longer exposure time to produce adequate dehydration compared to acetone. Paraffin, though essential for embedding, is not a dehydrating agent and is used in the later stages of tissue processing. Thus, acetone stands out as the optimal choice for rapid dehydration in urgent biopsy scenarios.