Which chemical is known for its accurate detection of blood but is avoided due to toxicity?

Benzidine is a chemical that has been historically used in forensic science for the detection of blood. It reacts with hemoglobin, producing a characteristic color change, which allows forensic scientists to confirm the presence of blood at a crime scene. However, benzidine is highly toxic and has been linked to serious health risks, including cancer. Because of its toxicity, its use has significantly declined, and safer alternatives are now commonly used for blood detection in forensic applications.

The other options do not serve the same dual purpose of detection and toxicity in the context of forensic science. Hemoglobin is a protein found in blood but does not possess the same properties for active detection methods. Chloroform and formaldehyde are chemicals used in various laboratory applications but are not specifically employed for blood detection like benzidine.