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Lugols Iodine: Everything You Need To Know

Lugol’s iodine has been in use for almost two centuries, valued for its versatility in both laboratory and practical applications. Whether used as a reagent, disinfectant, or emergency purifier, it remains one of the most recognisable iodine solutions. This guide explains what Lugol’s iodine is, how it works, where it is used, and how to handle it safely.

Brief History

Lugols Iodine in multiple pack sizes

Lugol’s iodine was first formulated in 1829 by the French physician Jean Guillaume Auguste Lugol. His intention was to create a stable iodine preparation that could be used in medicine, particularly for the treatment of tuberculosis and other conditions at the time. While medical understanding has advanced, the solution that bears his name has remained a standard reagent for nearly two centuries.

Throughout history, Lugol’s iodine has found varied uses:

19th and early 20th centuries – Widely used in medicine as a general antiseptic and as a way to deliver dietary iodine before modern iodised salt became common.
Microscopy and laboratory science – Adopted as a key staining reagent for identifying starch and highlighting cell structures.
Public health and emergencies – During nuclear accidents such as the Chernobyl disaster in 1986, iodine solutions including Lugol’s were distributed in some regions to saturate the thyroid with stable iodine and reduce uptake of radioactive iodine isotopes.
Food testing – Long established as a simple method of detecting starch in grains and vegetables, remaining useful for both science education and practical applications.

Why is Lugol’s Iodine Brown?

The distinctive brown colour of Lugol’s iodine comes from the chemistry of the solution itself. Iodine on its own is only a little bit soluble in water, but when combined with potassium iodide it forms triiodide ions (I₃⁻). These ions dissolve more readily and give the solution its deep brown appearance.

The shade varies with concentration: weaker solutions appear amber, while higher concentrations approach dark brown or almost black. Lugol’s iodine is also well known for its reaction with starch. When it binds to the helical structure of amylose in starch, the solution shifts dramatically to a blue–black colour.

Common Applications

Lugols in a beaker

Lugol’s iodine has a wide range of uses, both in scientific settings and practical environments:

Laboratory reagent – Frequently used for starch testing and as a staining solution in microscopy, particularly for identifying cell structures.
Antiseptic and disinfectant – Applied for cleaning surfaces and instruments in situations where its antimicrobial action is needed.
Water purification – In emergency situations, diluted Lugol’s iodine can be used to make contaminated water safer to drink.
Veterinary and aquaculture uses – Occasionally used to control microbial growth and maintain hygiene.
Educational demonstrations – Its starch reaction makes it a staple for teaching basic chemistry and biology.

Safety and Handling

Lugol’s iodine should always be handled with care, particularly at higher concentrations.

Protective equipment: Wear gloves and goggles to prevent skin or eye irritation.
Storage: Keep the solution in a cool, dry place, tightly sealed and away from direct light.
Handling: Work on a stable surface and avoid spills or splashes.
Concentration check: Always confirm the strength of the solution before use, as 3% and 15% solutions behave very differently.
Disposal: Follow local chemical disposal regulations rather than pouring into drains.

By following these guidelines, Lugol’s iodine can be used safely in laboratories, classrooms, and practical settings.

Concentrations Guide: Choosing the Right Strength

Lugol’s iodine is supplied in a range of concentrations, each suited to particular laboratory and practical applications. Selecting the correct strength ensures safe and effective use.

Concentration	Description and Typical Uses
Microscopy Solution	Specially prepared for use in staining and microscopic analysis. Commonly applied in cell biology for highlighting structures such as starch granules or nuclei.
3% Solution	A mild preparation suitable for educational demonstrations, starch testing, and general laboratory use. Its lower iodine content makes it easier to handle for routine experiments.
7% Solution	An intermediate strength, often used where a more concentrated reagent is needed for laboratory or research applications. Provides stronger staining and wider antiseptic action than lower concentrations.
12% Solution	Higher concentration solution suitable for more demanding tasks. Applied in laboratories for diagnostic staining, iodine–starch testing, and microbial inhibition.
15% Solution	The strongest Lugol’s iodine offered. Commonly used as a disinfectant and antiseptic, in Gram staining, histological work, contrast imaging, thyroid testing, and microbial control. Provides the deepest staining effect in chemical and biological tests.

Conclusion

Lugol’s iodine remains one of the most versatile and widely used iodine solutions. From its role in laboratory experiments to its effectiveness as a disinfectant and reagent, it continues to be a reliable choice.

APC Pure supply Lugol’s iodine in a range of concentrations and available in various pack sizes. Our solutions are manufactured with quality assurance and compliance in mind, making them suitable for laboratory, educational, and general chemical use.