2 March 2024

the lugol It is a solution of molecular iodine I2 and potassium iodide KI in distilled water. This mixture is used as an antiseptic and disinfectant, and as a reagent for the iodine test. Its origin dates from 1829, and it was invented by the French doctor Jean Guillaume Auguste Lugol, from whom it receives its name.

This product has a variable concentration of iodine and potassium, which is expressed in percentages. The characteristics of this solution reveal a dark brown color and a specific odor of iodine. It is a mixture that has multiple applications in chemistry and medicine, which we will explain below.

Who discovered the lugol?

Lugol’s discovery was made by Jean Guillaume Auguste Lugol, a french doctor born in Montauban in 1786. Lugol was interested in chemistry from a young age and carried out several studies on chlorine, bromine and iodine. In 1819 he published his doctoral thesis on the effects of chlorine in tuberculosis.

The French chemist dedicated himself to the treatment of infectious diseases, especially those of parasitic origin. In 1829 he first prepared the solution that bears his name, with the intention of using it as a remedy against syphilisscurvy and goiter.

Lugol was also a pioneer in public hygiene and the prevention of epidemics. He was also a member of the French National Academy of Medicine and received various decorations for his services. He died in Paris in 1851.

In what year was this iodine solution first prepared?

The iodine solution we know as Lugol’s was prepared for the first time in 1829 by the Frenchman Jean Guillaume Auguste Lugol. This prominent chemist published his formula in an article titled “Memoir on a New Iodine Preparation” in the Journal de Pharmacie et des Sciences Accessoires.

Lugol described his method for obtaining a stable solution of molecular iodine I2 in distilled water, by adding a suitable quantity of potassium iodide KI. The chemist explained that this solution had advantages over other ways of administering iodine, such as alcohol or ether, since it was more soluble, less irritating, and cheaper.

Lugol also detailed the chemical properties, physical and therapeutic of its dissolution, as well as the recommended doses for different diseases. The chemist claimed that his solution was effective in treating goitersyphilis, scurvy, ulcers, inflammations, bleeding and other conditions.

What is a dissolution?

A solution is a homogeneous mixture of two or more substances and is made up of a solute and a solvent. The solute is the substance that dissolves in the smallest amount, while the solvent is the substance that dissolves in the largest amount.

We understand that the lugol is a solution of iodine I2 (solute) and distilled water (solvent), and the solute and solvent therefore, they can be solid, liquid or gas. For example, air is a solution of gases such as nitrogen, oxygen, and carbon dioxide.

Solutions are characterized by having a variable composition, that is, they can be prepared with different proportions of solute and solvent. On the other hand, the concentration of a solution is the amount of solute in a given amount of solution or solvent. This concentration can be expressed in units such as grams per liter (g/L), moles per liter (M), or percentages.

What is the difference between a solution and a solution?

The terms solution and solution are often used interchangeably in common parlance, but they have different meanings in the scientific field. A solution is a homogeneous mixture of two or more substances, while a solution is a particular case of solution in which the solvent is a liquid.

For example, the lugol is a solution, since the solvent is water. However, air is not a solution, but rather a solution, since the solvent is a gas. Other common solutions are salt water, vinegar, or milk.

What is the lugol used for?

The lugol is very useful in various application areas. It is often used as disinfectant and antisepticfor water purification and in laboratory and medical analysis as a reagent for the iodine test.

It is a chemical mixture that serves to detect the presence of starch in food, since it reacts with it producing a violet color. It is also used as a stain for cells, and as a visual contrast in parasitology. However, lugol does not react with simple sugars such as glucose or fructose.

This dissolution used in medical tests for the detection of proteins and polysaccharides. It is also used as a nutritional supplement in order to cover iodine deficiencies, since the body needs this chemical element to produce thyroid hormones. Also, the iodine it is essential for the proper development and growth of children, and its deficiency can have serious consequences for their health.

In health, the lugol can be used to detect certain diseases, such as cervical cancer and some thyroid disorders.

  • Cervical cancer: Lugol’s iodine-iodinated solution used to detect hidden lesions. In normal cases, the cervical tissue sample that is placed in the solution should stain dark brown. If no staining occurs, it is considered to be a sign that abnormal cells are present in the tissue.
  • Thyroid disorders: This solution can also be used to assess thyroid function and diagnose conditions such as goiter, which is an enlargement of the thyroid gland.
  • Thyroid nodules: It is used to identify the nodules that produce too much or too little iodine. The normal thyroid will absorb iodine and will therefore turn dark in Lugol’s solution. If there is no iodine absorption, this may be a sign of hypothyroidism or thyroid cancer.

In this sense, the lugol has various uses in the areas of chemistry and medicinewhich we can group into three basic categories:

  • Disinfectant and antiseptic.
  • Iodine supplement.
  • Reagent.

Below we detail the utility of the lugol according to its category, in each of the application areas.

Uses of lugol’s in chemistry

This product It is used in the area of ​​chemistry with different objectivesbeing an excellent reagent and an oxidizing agent.

  • Reagent: to detect the presence of starch, glycogen and other substances containing hydroxyl groups. Lugol reacts with these compounds forming a dark blue or violet complex. This reaction is called the iodine test and is used to identify polysaccharides in food, plant, or biological samples.
  • Oxidizing agent: gives iodine atoms to other substances that are reduced. This product can oxidize alcohols, aldehydes, phenols, and other organic compounds. It can also be reduced to iodide when it reacts with reducing agents such as ascorbic acid or sodium thiosulfate.

Uses of lugol in medicine

In the area of ​​medicine, the lugol also has multiple uses. These range from medicinal to antiseptic, disinfectant, reactive and protective.

  • Disinfectant and antiseptic: eliminates or prevents the growth of pathogenic microorganisms such as bacteria, fungi or viruses. It is applied to the skin or mucous membranes to treat infections, wounds, burns or ulcers and is used to disinfect drinking water or medical instruments.
  • Iodine supplement: It provides the essential iodine for the functioning of the organism.
  • Regulator: It is necessary for the synthesis of thyroid hormones, which regulate metabolism, growth and development.
  • Reagent: to carry out diagnostic or therapeutic tests.
  • Medical treatments: Taken by mouth to prevent or treat goiter, hypothyroidism, cretinism, or iodine deficiency.
  • in laboratories: It is used to stain cells or tissues and make them more visible under a microscope or endoscope.
  • Protective: It is used to modify thyroid function or to protect it against exposure to ionizing radiation.

Uses of lugol’s as a reagent

Lugol’s is used as a reagent to perform various tests or experiments in the laboratory or in the classroom. Some examples are:

  • starch test: It is used to detect the presence of starch in foods such as potatoes, bread or bananas. By applying a drop of Lugol’s on the food and observing if it changes color.
  • glycogen test: to detect the presence of glycogen in biological samples such as liver or muscles. It works by placing a small portion of the sample in a test tube and adding lugol. It is then observed whether a red or brown precipitate forms.
  • amylase test: can demonstrate the activity of amylase, an enzyme that breaks down starch into glucose. Starch is mixed with saliva or pancreatic juice in a test tube and heated in a water bath. Lugol is then added and observed for color change.
  • Schiller’s test: Helps identify abnormal or cancerous tissue on the cervix. When the product is applied to the cervix through a colposcopy, it is observed if there are areas that do not stain brown.
  • gram testIt is used to differentiate Gram-positive from Gram-negative bacteria. To do this, a bacterial sample is fixed on a slide and stained with crystal violet. Then, lugol is added and washed with alcohol to observe under the microscope if the bacteria retain the violet color (gram-positive) or lose it (gram-negative).

Lugol’s reaction with other components

Lugol reacts with some components that contain polysaccharides, such as starch, glycogen and certain dextrins. These components form an inclusion complex with iodine which produces a blue-violet coloration.

This solution also reacts with the crystal violet stain, forming a water-insoluble complex that is used in the Gram stain. However, it does not react with simple sugars, such as glucose or fructose.

Components that react with lugol:

  • Polysaccharides: a reddish-brown coloration is produced.
  • Starch: a dark blue coloration is produced.

Components that do not react with Lugol:

  • Lipids and proteins: no staining occurs.

It’s important to put attention on the lugol should not be used to detect the presence of simple carbohydrates, such as glucose. This is only capable of detecting the presence of polysaccharides and starch.

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