What is luminol? How to make luminol at home

Some substances, participating in chemical reactions, have the ability to emit light. Every chemist-lover at least once produced a luminous liquid. This article will talk about what is luminol, how to cook it at home.

What is chemiluminescence?

Many reactions in chemistry take place with the release of energy. In most experiments, energy is released as heat. During the interaction of alkalis and acids, the solutions are heated. There are cases when the energy can appear in the form of an electric current (experiments with galvanic cells). When the reactants burn, the energy is converted into heat and light.

But there are reactions under which light is emitted, but there is no increase in temperature. This phenomenon is called chemiluminescence. The most striking example is the cold glow of phosphorus. It should be noted that in most chemical reactions with the release of "cold light" organic compounds are oxidized . Oxidizers are usually oxygen or hydrogen peroxide.

In nature, there are many substances that can emit light. But most often the luminescence turns out to be very weak and it can be detected only with the help of special equipment.

A relatively small group of organic and inorganic compounds is capable of bright and beautiful chemiluminescence. Examples include: luminol, siloxene, lofin, lucenigen and diphenyl oxalate.

What is luminol?

Luminol was synthesized in Germany in 1902, but received its real name later. It is a crystal of white or light yellow color, readily soluble in polar organic solvents. In water, luminol is completely insoluble.

It is an organic substance capable of releasing light when combined with hydrogen peroxide or other oxidizing agents. In neutral and slightly acid liquids, when illuminated with ultraviolet light, it fluoresces with a light blue light. In alkaline solutions (hydrogen peroxide), where the reaction takes place in the presence of catalysts - compounds of phosphorus, metal salts, hemin and hemoglobin - the luminescence turns out to be more saturated and bright.

The process consists of 2 stages. The acid is heated with hydrazine in an organic solvent with a high boiling point (3-ethylene glycol). As a result of condensation, a heterocyclic system of 5-nitrophthalylhydrazide is obtained. This compound is reduced with ammonium sulfide, resulting in the formation of luminol. With his hands, it can be obtained in laboratory conditions by synthesis from 3-nitro-phthalic acid.

Where is luminol used

The substance under consideration reacts remarkably with iron, which is part of the hemoglobin of the blood. Therefore, it is widely used by forensic experts in detecting traces of blood and fingerprints left at the crime scene. Luminol is used by scientists in carrying out various biological studies to detect iron, copper and cyanides.

Where to buy luminol solution

The cost of luminol is high enough. It can be searched at chemical forums, special bases or in pharmacies. If you do not know where to take luminol, then you can buy at the pharmacy "Galavit", which is available in tablets, ampoules and suppositories. The tablet contains 25 mg of the sodium salt of luminol. For 50 ml of 1% solution, 20 tablets are needed (package). The tablets are ground into a powder, and then water is added to it.

Luminous liquid with hydrogen peroxide

There are recipes for preparing luminous liquid from improvised means. But for the preparation of a solution it is best to use luminol, because it gives a smooth and soft bluish light. Before starting work, always protect open areas of the body with a dense cloth, and put gloves on your hands.

We prepare luminol at home under the classic (first) recipe:

• Luminol - 2-3 grams.
• Water - 0,1 liters.
• A solution of hydrogen peroxide (3%) - 0.08 liters.
• Sodium is 0.01 liters.
• Copper sulfate - 3 grams.
• Dyes (chopped, brilliant green or any other).
• Glassware (flasks or jars).

Cooking process:

• Pour water into the glass container and add luminol. We carefully mix the crystals in water so that they dissolve as much as possible in it.
• Add hydrogen peroxide to the resulting solution.
• In the resulting composition, add copper sulfate. Replace vitriol can be ferric chloride or blood salt.
• The most recent add to the composition of caustic sodium.
• In the room turn off the light. The resulting composition should radiate a bright blue glow. If you need a different color, then add the desired fluorescent dye to the solution.

The second option:

• The solution of luminol (3%) was 5 ml.
• Hydroperite (3%) - 10 ml.
• Washing powder with water - 20 ml.
• Potassium permanganate.
• Any glass jar or jar.

Stages of work:

• In a container we pour solutions of luminol, washing powder and hydrogen peroxide.
• Gently rub several crystals of potassium permanganate and add it to the total composition.
• To see what luminol is and how it will manifest its properties, turn off the light in the room. The liquid will emit a beautiful glow. If the solution is stirred periodically, a sparking foam will appear on its surface.

Preparation of a solution with dimethylsulfoxide

A more interesting option would be the oxidation of luminol by air oxygen in a dimexide medium. The glow appears on the interface between the air and the water.

For the preparation of the composition we will need:

• Luminol - 0.15 grams.
• Dimexide (dimethylsulfoxide) - 30 ml.
• Dry alkali - 35 grams.
• Any fluorescent dye.
• High glassware.

Stages:

• Thoroughly mix in the flask dimexide, luminol and alkali.
• Close the flask tightly with a lid.
• In the room turn off the light.
• Flask slightly shake until a bluish glow. To change the color, add a fluorescent dye.
• If the glow has lost its brightness, then you can open the capacitance. When the air enters the flask, the solution again becomes bright and saturated.

Cooking tips

A lot of alkali in the solution is not recommended, because it dissolves very poorly and turns the liquid into a thick porridge. A suspension of luminol, dimexide and alkali can be stored for a rather long time. When adding an oxidizer, the glow will be uniform. Its duration depends on the amount of hydroperite and luminol and can reach 40 minutes. But from the overabundance of luminol, the luminescence becomes weaker.

It should be noted that the brightness and duration of the luminescence will also depend on the concentration of luminol. Strongly diluted solutions give a weak but prolonged glow. The high concentration of the substance forms a strong brightness of the entire solution. The color of the glow can vary from blue to green. In more saturated formulations containing a high concentration of blood salt, a green glow is obtained.

Is it possible to replace luminol?

There are situations when it is necessary to prepare a luminous liquid without luminol. To do this, take boric acid and a few drops of fluorescein. These substances must be mixed and heated on a metal plate. The liquid will glow in the dark for about a minute.

To understand what luminol is, it's best to try to get it yourself. As they say, it's better to see once than hear a hundred times. But do not forget that any experiments involve interaction with corrosive and harmful substances. Therefore, it is necessary to comply with safety regulations.