Why peroxide bubbles

This relied on the chemistry of phenolphthalein, well-known today to students as an acid-base indicator. Phenolphthalein is colourless in acid but turns a deep pink in a basic solution. In this case, though, the important feature is that phenolphthalein can be reduced with zinc into colourless phenolphthalin, which along with a base is present in the test reagent. In the usual process, a drop of alcohol is added to an unknown stain to dissolve any hemoglobin that may be present, followed by rubbing with a swab that has been treated with the Kastle-Meyer reagent.

A drop of hydrogen peroxide is then applied to the swab. If hemoglobin is present, the hydrogen peroxide decomposes to yield oxygen that in turn oxidizes the phenolphtalin to phenolphthalein. Since the solution is basic, a pink colour develops indicating the presence of blood. The test is very sensitive, but is not specific for human blood. Animal blood will also yield a positive reaction as will oxidizing agents such as some metal ions.

The technique is to spray the suspect area with a solution of luminol and hydrogen peroxide. If blood is present, the peroxide will yield oxygen that then reacts with luminol to produce a blue glow.

This reaction was first noted in by the German chemist H. Albrecht and was put into forensic practice in by forensic scientist Walter Specht. Even dried and decomposed blood gives a positive reaction with the blue glow lasting for about 30 seconds per application. The glow can be documented with a photo but a fairly dark room is required for detection. The reaction is so sensitive that it can reveal blood stains on fabrics even after they have been laundered.

Blood and cells in the human body contain an enzyme called catalase. Damage to tissue releases the catalase, which catalyzed the decomposition of hydrogen peroxide. Catalase supports up to , reactions per second. Iron from the hemoglobin in blood also catalyzes peroxide decomposition. So, blood packs a double whammy when it comes to peroxide bubbling because it contains both iron and catalase from damaged blood cells.

Sometimes minor bubbling occurs because skin naturally hosts Staphylococcus bacteria, which produce catalase. Simply splash a small amount into a sink and look for bubbles near the drain. Metals catalyze peroxide decomposition much like catalase. Another simple test is splashing peroxide onto a cut potato. Once the catalase is all used up, the organism's defense system is gone and is fully exposed to the destructive effects of the peroxide. And since hydrogen peroxide possesses a non-discriminating ability to kill, it's not recommended to use on open wounds.

It kills healthy cells, and damages platelets and connective tissues, and as a result can severely inhibit the body's ability to repair itself.

It's also really important to remember that just because you don't see foaming, it doesn't mean that hydrogen peroxide isn't killing, or that germs aren't present. It just means that there is no catalase. Some cells and most viruses don't produce catalase, but that doesn't mean that hydrogen peroxide is not actively killing them.

It just means that they don't have the ability to fight the peroxide off. Looking for a great cleaner with powerful hydrogen peroxide and amazing scents?

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