How to use Luminol

Details:

Luminol, commonly known as luminol, is a mixture of luminol and hydrogen peroxide used in criminal investigation. There is iron in the blood. Iron will accelerate the oxidation process of luminol and hydrogen peroxide. However, during the oxidation reaction, part of the energy released will exist in the form of photons, which can continuously emit fluorescence for 30 seconds in the dark.

How sensitive is luminol in detecting blood

Luminol detection of blood is very sensitive, even if a drop of blood drops into a large bathtub, it can also be detected. It is necessary to wash the scene to the level that luminol can not detect, unless it is not detected, as long as it is detected, there is basically no possibility that it can not be detected.

How do forensic doctors detect luminol

In a dark room, the luminescent ammonia is evenly sprayed on the surface of an object, and a small amount of active oxidant will make the luminescent ammonia emit visible blue light. The glow lasts only about 30 minutes, but investigators can record the effect with long exposure photos. Crime scene investigators must spray luminol evenly to avoid misleading results, because traces of blood appear to be more concentrated in more areas sprayed with luminol. The luminescent intensity of luminol does not indicate the amount of blood or other activators, but only the distribution of these substances in the explored area.

Dry or putrid blood can make luminol glow more strongly

In 1937, German forensic scientist spercht carried out extensive research on the detection of blood at the crime scene. In 1939, two American Pathologists made three important observations on luminol ammonia: Although luminol ammonia test is not certain, it can rapidly detect large areas with suspicious materials; Compared with fresh blood, dry blood or rotten blood can make luminol more intense; If the luminescence disappears, a fresh luminescent ammonia hydrogen peroxide solution can be used to reconstruct the luminescence, so that the dry bloodstain can emit light repeatedly.

The disadvantage of luminol in blood test

Some shortcomings of luminol limit its utility in crime scene investigation. In addition to blood, other substances (such as copper and copper containing compounds) and optical bleaching agents also make luminescent ammonia glow. Therefore, if someone has washed the crime scene with bleach, the bleach residue will cause the whole crime scene to emit blue light, which will cover up the effective evidence at the scene

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