Which of the following compounds acts as both a fixative and a dehydrating agent?

Acetone is a compound that serves as both a fixative and a dehydrating agent in histopathology. As a fixative, it preserves tissue by denaturing proteins and coagulating cellular components, which helps maintain the structure of the tissue for microscopic examination. Simultaneously, acetone acts as a dehydrating agent by removing water from the tissues. This dual function makes it particularly valuable in histological preparations where maintaining cellular integrity while preparing samples for embedding in paraffin or other materials is essential.

In the context of histopathology, the other options perform specific functions but do not fulfill both roles simultaneously. Formaldehyde is primarily used as a fixative for preserving cellular structures but does not dehydrate tissues effectively. Absolute ethanol is very effective as a dehydrating agent and is often used in the dehydration step of tissue processing, but it is not typically considered a primary fixative. Xylene is primarily used as a clearing agent after dehydration and does not function effectively as a fixative.

In summary, acetone's ability to both fix and dehydrate tissues makes it a unique and useful compound in histopathological techniques.