Iodine crystal

Iodine crystal

A solid, gray substance which sublimates when heated. Its solution in alcohol is called ´tincture of iodine´, it is a disinfectant.



iodine crystal, molecular lattice, halogen, homonuclear molecule, sublimation, crystal lattice, disinfection, thyroid gland, nonpolar, inorganic chemistry, chemistry

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Iodine crystal I₂


Molar mass: 253.81 g/mol

Melting point: 113.6 °C (236.48 °F)

Boiling point: 185.2 °C (365.36 °F)

Density: 4.93 g/cm³ (0.178 lb/in³)


Iodine is a solid, gray, crystalline substance with a characteristic odor. It dissolves weakly in water but dissolves well in alcohol (turning brown) and in petrol (turning purple). When dissolved in alcohol, it is called iodine tincture. It also dissolves well in potassium iodide solution due to the formation of triiodide ions.

When heated carefully, iodine forms a purple gas, skipping the liquid phase. This process is called sublimation. Iodine turns blue in contact with starch; this property can be used for the detection of either starch or iodine. Iodine is an oxidant.

Occurrence and production

Iodine is the 60th most common element in the Earth’s crust. Natural saltwaters also contain iodine. It is an important trace element for the human body, essential for the proper functioning of the thyroid gland. Iodine deficiency can cause goiter, obesity, fatigue, and developmental delays as well as dwarfism in newborn babies and children. Molecular iodine can be prepared by oxidizing iodides with chlorine.


Iodine can be used either in the elemental or bound state for disinfection (as iodine tincture) and for the iodination of table salt (as potassium iodide). Iodine-131, a radioactive isotope of iodine, is used in the treatment of thyrotoxicosis. Iodine is also used in producing dyes, for detecting starch in analytic chemistry and as a catalyst.

Related items

Iodine (I₂)

A solid, gray substance which sublimates when heated. Its solution in alcohol is called tincture of iodine, it is a disinfectant.

Hydrogen-iodide (HI)

A colorless, heavier-than-air gas with a pungent odor.

Bromine (Br₂)

One of the halogens, it may cause skin irritation.

Chlorine (Cl₂)

A yellow-green toxic gas with a strong odor, one of the halogens.

Comparison of halogens

Halogen elements are a group in the periodic table consisting of five chemically related elements, fluorine, chlorine, bromine, iodine, and astatine.

Silver iodide (AgI)

A light yellow compound formed in the reaction of silver nitrate and potassium iodide.

Fluorine (F₂)

The lightest halogen, a pale yellow-green, toxic gas, extremely reactive. Its best known compound is teflon.

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