Is potassium iodide flammable? (A 5-point Guide)

This article will answer the following question: “Is potassium iodide flammable?”. We will explain what the chemical compound is, what it is used for and the hazards related to handling and ingesting it.

Is potassium iodide flammable?

No. Potassium iodide (KI) can’t catch fire. KI is an inorganic salt that’s considered non-combustible. It can catch fire, will not ignite, won’t enhance a fire if tossed into one, and no flames would arise from it.

What is potassium iodide?

Potassium iodide (KI) is a form of salt. It’s commercialized as a chemical compound, medication, and dietary supplement.

As a medication, it is used to treat hyperthyroidism and goiter, in radiation emergencies, and to protect the thyroid gland in the treatment of certain types of cancer.

The supplementation of KI must be allowed by a doctor because potassium iodide overtake can be as harmful as the lack of it. Use KI only if instructed to do so.

Knowing that iodine deficiency can be easily avoided, some governments request manufacturers to supplement table salt with iodine. Around 88% of all households worldwide use iodized salt, but it’s still a problem in some places.

Iodine chemistry

Iodine is a big chemical element. 

It has 53 protons in its nucleus. The biggest a nucleus is, the higher the number of isotopes a chemical element has. You can check more atomic information in the picture below.

Isotopes and radioactivity

There are 37 iodine isotopes known by mankind, but only one of them is stable, the “127I”. This number is the weight each atom has. This is the one iodine atom we can find in iodophor solutions, supplements, and any other commercially available form.

Other iodine isotopes are radioactive, have a short life and suddenly are torn apart to produce lighter compounds such as Antimony and Tellurion.

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

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 in accidental environmental contaminations. 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 close to radioactive contaminations, to reduce the uptake of radioactive iodine.


I2 in its elemental form is barely soluble in water.

To dissolve one gram in water is required 3450ml (116.6 fl oz, or 3.45 liters) of pure water, at 50ºC. Although, the compound is more soluble in organic solvents such as hexane and tetrachloride.

Potassium iodide, although, is highly soluble in water, like other iodide salts. 1ml (0.000290 fl oz) of water can solubilize 1760mg of it, at 60 °C (140 °F).

What is a salt?

Salt is a chemical compound that has an ionic form, it’s made of a cation and an anion, which respectively have positive and negative electrical charges.

Normally, in order for salt to become stable, the charges must cancel each other, so there are no net electrical charges.

Salts can present many physical forms, different solubilities, odors, tastes, melting points, and conductivity.

When a salt has a high solubility in water it is considered a strong salt. It happens because its electrolytes can easily achieve an ionic form in a water solution, which also means that they’re stable.

Iodide salts are highly water-soluble. This is the main reason why potassium iodide is much more used than elemental iodine (barely soluble in water). It’s much easier to handle a compound if it dissolves in water.

Is potassium iodide flammable?

Potassium iodide is normally commercialized in a powdery form.

At first, it may look that any solid material is flammable when crushed into thin particles, but this is not true.

It is true that when in a powder form, a compound has a higher contact surface, so the particles can participate in chemical reactions more easily, but the compound must be reactive to do so.

Potassium iodide can’t burn because it is an inorganic compound. But what does that means?

Well, the difference between something organic and inorganic relies on carbon. Carbon atoms have diverse chemistry that allows them to form many types of molecules, and all forms of fuel we know.

Fire may seem like a synonym for heat, but heat is just a part of the fire. We will discuss more of that in another topic below. 

What matters for now is the following: potassium iodide it’s not flammable because it’s not even combustible. It can’t catch fire. Even if was tossed into flames, it wouldn’t make the fire grow.

And iodine flammable? Is it a fire hazard?

No. Any pure form of iodine is not flammable. The iodine in potassium iodide is also 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. No matter if the fuel is liquid or solid, it gotta become airborne so the reaction can happen.

But iodine is 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.

Resuming: 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. 

But iodine is an oxidizing agent, it might interact with the fuel during a fire, so it’s possible that by tossing pure iodine into the fire it would grow even bigger. But this isn’t true for potassium iodide.

Potassium iodide, although, is not considered a good oxidizing agent.

Ok then. What is fire?

Fire is something intrinsically related to life.

Fire is not an element, like the other things in the periodic table. Fire is a consequence of how organic matter burns.

Fire is something that started on our planet only after the plants settled on the land, which occurred more or less 400 million years ago. Before that, any place on earth hasn’t ever seen a fire.

But how about meteors? Volcanic Eruptions? How could they not be related to fire?

Well, they are not. Anything can heat and have its temperature felt risen a lot, but not everything will burn because of that. Although, things can decompose if reach too much a temperature.

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

All three happen at once during a fire. How fire will look depends on how these three events happen. 

For example, in a blue flame from an oven, oxidation is almost the only thing that happens, because the fuel is already vaporized (it is a gas), and its chemical composition is simple (the carbon chains are small), so the oxidation happens pretty quick.

In a fireplace, although, we can see many more 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. Potassium iodide, although, can barely do that.

Most strong salts can’t participate in a combustion reaction, can’t suffer pyrolysis (a breakdown through intense heat), and can’t evaporate. Because of that, we can assure that potassium iodide will not burn.

But how about potassium iodide preparations? What else is in a KI supplement or medication?

Potassium iodine safety data sheets

To have a definitive answer on rather Potassium Iodine is flammable or not, we must search for specific safety data information provided by companies that produce it as a product.

None of the following products are considered flammable. All of them consider the product may cause damage to organs (thyroid gland) through prolonged or repeated exposure (if swallowed).

  • Potassium iodide (for laboratory use);
  • Potassium iodide (for several uses, including: in a lab, for human and vet use, in treatment of thyroid disorders, as an ingredient in personal hygiene products, and topical deodorizing agent for livestock;
  • Another one, similar to the others;
  • Potassium iodide 0.1M (in aqueous solution).


Potassium iodide is a solid chemical compound that can be used as a nutrient for us and livestock, and as medicine. It is an inorganic salt that can’t catch fire. No flames would rise if tossed into a fire.

Frequently Asked Questions (FAQS): Is potassium iodide flammable?

Is potassium iodide ionic or covalent?

It is ionic. This is because potassium (K) and iodine (I) present very different electronegativities. The chemical bonding they present is, therefore, very strong, considered ionic.

is potassium iodide a reducing agent?

Yes. In an aqueous solution, potassium iodide will liberate potassium cation (K+) and iodide anion (I). Iodide will enhance the reduction of other species because it will provide electrons.

potassium iodide is added to lead nitrate?

If potassium iodide (KI) is added to lead nitrate (PbNO3)2, a chemical reaction will happen with the exchange of electrolytes. The lead will react with iodine and create a yellowish precipitate.

The reaction is named: a double displaced reaction.


What was missing from this post which could have made it better?

Leave a Comment