Final answer:
The chemical used to detect wiped-away blood that becomes luminous in the dark is luminol. Luminol reacts with the iron in hemoglobin, producing light and making the blood glow in the dark. This reaction is commonly used in forensic investigations.
Step-by-step explanation:
The chemical used to detect wiped-away blood that becomes luminous in the dark is luminol. Luminol is a compound that reacts with the iron in hemoglobin, which is found in blood. When luminol comes into contact with blood, it undergoes a chemical reaction that produces light, making the blood glow in the dark. This reaction is often used in forensic investigations to detect traces of blood at crime scenes.