Is iodine flammable corrosive or combustible? (A review)

This article will answer the following question: “Is iodine flammable corrosive or combustible?”. We will explain if iodine can catch fire, if it’s a corrosive agent, and if it is a combustible molecule.

Is iodine flammable corrosive or combustible?

Iodine is not flammable, and neither is combustible. Although, it’s a very corrosive substance and an oxidizing agent that can promulgate fire.

What is Iodine?

Iodine is a chemical element.

It is the fourth halogen, a member of group 17 in the periodic table. It’s the heaviest member of its group, and also the heaviest essential mineral nutrient for our bodies.

It exists in many forms. We usually don’t encounter it in its pure form, only in salts or in a liquid solution. Commercially available forms of iodine are not pure forms of it.

Iodine is solid and has the formula I2 in its pure crystalline form, but it can also be gas and present the same formula. It also exists as Iodide (I), iodate (IO3), some kinds of acid, and periodate anions (IO4, IO6−5, and others).

Iodine’s primary use is in our nutrition. We require Iodine in our bodies so it can synthesize thyroid hormones. The lack of it may lead us to disinvolve goiter disease and prejudice the central nervous system development in fetuses and infants.

Knowing that iodine deficiency is prejudicial, some governments oblige manufacturers to supplement kitchen salt with iodine. Around 88% of all households worldwide use iodized salt, but it’s still a problem in some underdeveloped countries.

Some forms of salts considered gourmets, such as Himalayan Pink Salt, Kosher salt, Smoked salts, and others, may not have iodide added to their formulation.

If you mainly consume a salt that doesn’t contain iodine, consider speaking to a doctor about starting iodine supplementation.

Industrially, iodide anion is used as a catalyst in the production of acetic acid, and in organic chemistry to synthesize certain polymers.

Iodine properties

  • State: solid
  • Melting point: (I2) 386.85 K ​(113.7 °C, ​236.66 °F)
  • Boiling point: (I2) 457.4 K ​(184.3 °C, ​363.7 °F)
  • Density: 4.933 g/cm3
  • Triple point: 386.65 K, ​12.1 kPa
  • Critical point: 819 K, 11.7 MPa
  • Heat of fusion: (I2) 15.52 kJ/mol
  • Heat of vaporisation: (I2) 41.57 kJ/mol
  • Molar heat capacity: (I2) 54.44 J/(mol·K)
  • Natural occurrence: primordial
  • Crystal structure: ​face-centered or orthorhombic
  • Thermal conductivity: 0.449 W/(m⋅K)
  • Electrical resistivity: 1.3×107 Ω⋅m (at 0 °C)
  • Magnetic ordering: diamagnetic
  • Molar magnetic susceptibility: −88.7×10−6 cm3/mol (298 K)
  • CAS Number: 7553-56-2
  • Oxidation states: −1, +1, +3, +4, +5, +6, and +7

What are iodine sources?

The biggest sources of natural iodine are in seaweed foods such as kelp, nori, kombu, and wakame. Eggs and dairy products are also good sources.

Although, the amount of iodine in natural foods depends on the animals, especially when it comes to dairy products. Seaweed normally doesn’t vary much.

Other important sources of iodine are infant milk formulas and human breast milk.

Bread, fruits, vegetables, pasta, hamburger buns, hot dog buns, soy milk, and apple juice are examples of bad sources of iodine.

Is iodine combustible?

No. Combustibles are molecules that can ignite and generate heat by doing so. Normally, combustible sources are fuels. Iodine is not an organic compound.

Nearly anything that’s made from organic compounds (which essentially means, it’s made of carbon and hydrogens above all) can eventually catch fire.

A fire is a result of the combustion reaction between a fuel and oxygen. Combustion is one type of thermal decomposition.

There are three ways in which the thermal decomposition of organic matter happens: oxidation, pyrolysis, and evaporation/ vaporization.

In a wood fire, we can see many yellow and red flames, smoke, fumes, and all kinds of byproducts from incomplete combustion. This happens because the chemical reactions are much more complex since the fuel has a very different composition.

When wood burns, the solid material is constantly being stimulated to a vapor-like state and suffers all kinds of breakdowns before finally reacting with oxygen (combustion). All these chemical reactions lead to many byproducts, many of which are toxic to us.

Iodine, although, doesn’t suffer a reaction with oxygen like that. But similarly to fuels, iodine can assume a vapor state of matter, become airborne and cause harm to our health.

We can say that iodine presents some level of thermal decomposition, but no fires.

Is Iodine flammable?

No. In order for iodine to become flammable, first, it has to be combustible, which is not true.

Iodine is an inorganic compound that can’t react with the air’s oxygen to produce a flame.

Combustible or flammable?

Flammable is usually a term used to denote a compound that’s capable of igniting easily and burning quickly.

Combustible, although, is simply something that can catch fire.

These are general definitions. To correctly assess the information about how flammable a substance is, much more context and research are required. 

There are many scenarios in which the same compound could behave differently when it comes to combustion.

Is iodine corrosive?

Yes, iodine is very corrosive.

The thermal decomposition of iodine yields corrosive vapors that can be really dangerous.

The international pictogram for corrosive substances.

Besides, iodine can be corrosive to our skin by the touch.

At the same time, a small amount of iodine can be beneficial to our body, it can serve as iodine supplementation.

Corrosive compounds are things that can react chemically, destroy or dissolve other substances. This destruction happens in minutes.

It’s common that highly oxidative substances are also corrosive. 

Corrosive also can be called caustic or irritant. Different from a poison, corrosive compounds are substances that immediately become dangerous for living tissues.

Iodine’s medical use

Iodine can mostly be used to treat iodine deficiency, which can lead to goiter, and as an antiseptic.

Iodine and iodophor are widely used worldwide as antiseptics. Its medicinal use is so important that is part of the World Health Organization’s List of Essential Medicines.

Thyroid issues

Iodine is an essential component in the production of thyroid hormones, it can regulate many biochemical reactions in our body, including protein synthesis and enzymatic activity.

The thyroid’s primary function is to regulate the thyroid-stimulating hormone, which is secreted by the pituitary gland.

Nutrient deficiency

There are many foods that are good sources of iodine. Even so, many soils worldwide contain variable iodine contents, so nutrient deficiency can strike people from those regions.

For this reason, salt iodization programs had being implemented in many countries, which have dramatically reduced the prevalence of iodine deficiency worldwide.

The daily intake recommendation of iodine varies according to a person’s age, but it stabilizes from 18 years old on. Although, it is higher for pregnant and lactating women of all ages.

Radioactive iodine

The “131I” isotope of iodine is commonly produced in fission nuclear plants, it’s created inadvertently in nuclear reactors by the decay of the “132Te” isotope.

The half-life of this Tellurium compound is around 3 days, which may not look much, but it’s more than enough to cause serious problems during nuclear accidents. But our body can’t distinguish between Iodine atoms. 

Our thyroid will consume the radioactive atom unwillingly, which can cause many problems. To prevent that, Iodine supplements are given to populations that suffer from radiation emergencies, to reduce the uptake of radioactive iodine.

At the same time, high intakes of harmless iodine compounds can cause some of the same symptoms as iodine deficiency.

Is iodine flammable? Is it a fire hazard?

No. Any pure form of iodine is not flammable.

Part of the reason that makes a fuel catch fire is the combustion reaction. When something reacts with oxygen, and this reaction liberates energy from beneath the fuel chemical bondings, the fire appears as a combination of heat and light.

This same reaction can also have another name: oxidation.

Although it’s not like any other oxidation, it’s a reaction that happens in a gas state. Even if the fuel is liquid, it gotta become airborne so the reaction can happen.

But iodine is already an oxidation agent, it already acts chemically similar to oxygen. This means that a reaction between iodine and the air’s oxygen wouldn’t happen normally and that no energy would be generated by it.

Summarizing: iodine can’t catch fire because the chemical reaction that generates the flames can’t happen. Iodine and oxygen gas can’t react with each other under normal circumstances.

Iodine can still become airborne by reaching a vapor form if it’s heated. It doesn’t generate flames but unleashes toxic vapors.


Iodine is considered to be corrosive, especially when in a gas form. Iodine is not considered combustible, nor flammable. Although, since it’s a strong oxidizer, iodine can enhance the combustion of sources of fuel, during an eventual fire.

Frequently Asked Questions (FAQS): Is iodine flammable corrosive or combustible?

Does iodine corrode metal?

Iodine does present some corrosiveness against metal if in an aqueous form but is not a strong corrosion agent in this case.

When it comes to live tissues, iodine is considered corrosive, especially in vapor form.

Is iodine toxic to humans?

Humans do require some concentration of iodine in their diet, but an excess can be equally dangerous.

The correct daily intake of iodine is easily achievable thanks to salt iodization programs that oblige table salt manufacturers to add iodine in their formulations.

Is iodine good for covid?

Iodine as an antiseptic agent can be good to eliminate Covid on surfaces, but not on our bodies.

By ingesting iodine, it won’t get in contact with the Covid virus in our cells (assuming that the person is infected), so it will not do any good. It also wouldn’t serve as prophylactic medicine.

Iodine is a great oxidizing agent, it reacts with organic compounds.

The antimicrobial action of iodine is certain, but its specific mode of action is unknown. We can assume that it attacks some amino acids, nucleotides, and fatty acids, resulting in cell death.


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