Some substances, participating in chemical reactions, have the ability to emit light. Every amateur chemist at least once made a luminous liquid. This article will discuss what luminol is, how to prepare it at home.
What is chemiluminescence?
Many reactions in chemistry proceed with the release of energy. In most experiments, energy is released in the form of heat. When alkalis and acids interact, the solutions heat up. There are cases when energy can manifest itself in the form of an electric current (experiments with galvanic cells). When reactants burn, energy is converted into heat and light.
But there are reactions in which light is emitted, but no increase in temperature is observed. 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. The oxidizing agents are usually oxygen or hydrogen peroxide.
There are many substances in nature that can emit light. But most oftenthe glow is very weak and can only be detected using special equipment.
A relatively small group of organic and inorganic compounds are capable of bright and beautiful chemiluminescence. Examples include: luminol, siloxene, lofin, lucegenin and diphenyl oxalate.
What is Luminol?
Luminol was synthesized in Germany in 1902, but got its real name later. It is white or light yellow crystals, readily soluble in polar organic solvents. Luminol is completely insoluble in water.
This is an organic substance capable of emitting light when combined with hydrogen peroxide or other oxidizing agents. In neutral and slightly acidic liquids, when illuminated with ultraviolet light, it fluoresces with light blue light. In alkaline solutions (hydrogen peroxide), where the reaction proceeds in the presence of catalysts - phosphorus compounds, metal s alts, hemin and hemoglobin - the glow is more saturated and bright.
The process consists of 2 stages. The acid is heated with hydrazine in a high boiling point organic solvent (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 your own hands, you can get it in the laboratory by synthesis from 3-nitro-phthalic acid.
Where is luminol used
The substance in question 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 various biological studies to detect iron, copper and cyanide.
Where to buy luminol solution
The cost of luminol is quite high. You can search for it on chemical forums, special databases or in pharmacies. If you do not know where to get luminol, then you can buy it at the Galavit pharmacy, which is available in tablets, ampoules and suppositories. The tablet contains 25 mg of luminol sodium s alt. For 50 ml of a 1% solution, 20 tablets (package) are required. Tablets are crushed into powder, and then water is added to it.
Glowing liquid with hydrogen peroxide
There are recipes for making a luminous liquid from improvised means. But for the preparation of the solution, it is best to use luminol, because it gives an even and soft bluish light. Before starting work, be sure to protect exposed areas of the body with a thick cloth, and put on gloves on your hands.
Let's prepare luminol at home according to the classic (first) recipe:
- Luminol - 2-3 grams.
- Water - 0.1 liters.
- Hydrogen peroxide solution (3%) - 0.08 liters.
- Caustic sodium - 0.01 liters.
- Copper vitriol - 3grams.
- Dyes (chopped, brilliant green or any other).
- Glassware (flasks or jars).
Cooking process:
- Pour water into a glass container and add luminol. Thoroughly mix the crystals in water so that they dissolve as much as possible in it.
- Add hydrogen peroxide to the resulting solution.
- Add copper sulfate to the resulting composition. You can replace vitriol with ferric chloride or blood s alt.
- The last thing we add to the composition is sodium hydroxide.
- Turn off the lights in the room. The resulting composition should emit a bright blue glow. If a different color is needed, then add the desired fluorescent dye to the solution.
Second option:
- Luminol solution (3%) - 5 ml.
- Hydroperite (3%) - 10 ml.
- Water Laundry Detergent - 20 ml.
- Potassium permanganate.
- Any glass vessel or jar.
Steps of work:
- Pour solutions of luminol, washing powder and hydrogen peroxide into the container.
- Gently grind a few 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 periodically stirred, a sparkling foam will appear on its surface.
Preparing a solution with dimethyl sulfoxide
A more interesting option would beoxidation of luminol with atmospheric oxygen in a dimexide medium. Glow occurs at the interface between air and water.
To prepare the composition we need:
- Luminol - 0.15 grams.
- Dimexide (dimethyl sulfoxide) - 30 ml.
- Dry alkali - 35 grams.
- Any fluorescent dye.
- Tall glassware.
Steps:
- Thoroughly mix dimexide, luminol and alkali in a flask.
- Close the flask tightly with a lid.
- Turn off the lights in the room.
- Shake the flask slightly until a bluish glow is obtained. To change the color, add a fluorescent dye.
- If the glow has lost its brightness, then you can open the container. When air enters the flask, the solution becomes bright and saturated again.
Cooking Tips
It is not recommended to add a lot of alkali to the solution, because it dissolves very poorly and turns the liquid into a thick porridge. A suspension of luminol, dimexide and alkali can be stored for quite a long time. When an oxidizing agent is added, the glow will be uniform. Its duration depends on the amount of hydroperite and luminol and can reach 40 minutes. But from an excess of luminol, the glow becomes weaker.
It should be noted that the brightness and duration of the glow will also depend on the concentration of luminol. Highly dilute solutions give a weak but long-lasting glow. A large concentration of a substance forms a strong brightness of the entire solution. The glow color can change from blue to green. In moresaturated compounds containing a high concentration of blood s alt, a green glow is obtained.
Can I 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 is better to try to get it yourself. As the saying goes, it's better to see once than hear a hundred times. But do not forget that any experiments involve interaction with caustic and harmful substances. Therefore, safety precautions must be observed.
