Fixatives containing chromate salts usually require which washing step before processing?

• A. Washing in water
• B. Washing in 70% ethanol
• C. Rinsing with saline
• D. No washing is required

Answer: (A)

Washing in water is needed because fixatives containing chromate salts leave water-soluble chromium compounds in the tissue. If these salts aren’t removed, they can continue to react during processing, potentially causing over-fixation and artifacts such as crystal formation during dehydration and clearing. Water effectively dissolves and carries away these salts, stopping their action before processing. Washing with ethanol wouldn’t remove the water-soluble chromate adequately and can introduce other issues, while rinsing with saline leaves salts behind and may promote unwanted deposits. Skipping a wash allows residual chromate to interfere with subsequent steps and staining.