Iodine crystal, with a chemical formula of I2, is an inorganic compound. It is a blue-black solid with unique physical and chemical properties.

Here are some key features and uses of iodine crystal:

1. Solid form: Iodine crystal exists as a solid, displaying a characteristic blue-black crystalline structure.

2. Volatility: At room temperature, iodine crystal slowly vaporizes into a purple-colored gas. This property finds widespread use in distillation and handling of volatile substances in laboratories and industries.

3. Solubility: Iodine crystal exhibits good solubility in many organic solvents such as ether, benzene, and chloroform. This makes it widely used as a catalyst or reagent in organic synthesis reactions.

4. Disinfectant: Iodine crystal possesses bactericidal and disinfectant properties, thus finding extensive application as a disinfectant and preservative in medical and sanitation fields.

5. Iodized salt additive: Iodine crystal can be used to prepare iodized salt additives such as potassium iodide and sodium iodide. These additives are employed in food processing to prevent iodine deficiency disorders and maintain the recommended intake of iodine for the human body.

   Medicine

   
   (1)Iodide
    

       Elemental iodine and solutions containing the triiodide anion I3− (which can be made by adding iodide to an aqueous solution of insoluble elemental iodine and which can be produced by the reverse reaction of the preparation process) are disinfectants. It can also be used to treat iodine deficiency. Iodine can also be produced from iodophor. Examples of iodophor include:
   
   a.tincture of iodine, iodine ethanol solution, or iodine and sodium iodide dissolved in a mixture of ethanol and water solution.

   b.lugol iodine, iodine and iodide solution, the iodine mainly exists in the form of three iodide.

   c.povidone iodine

   d.Iodine-V: I2 and cage of fulvic acid complex, is the crystal soluble in water. Unlike other iodophor, the Iodine in Iodine-V exists only as I2.
    

       Iodine's antibacterial action is rapid and effective at low concentrations, so it can be used in surgery. The exact antibacterial mechanism of iodine is unknown, but it penetrates microorganisms and attacks certain amino acids (such as cysteine and methionine), nucleotides, and fatty acids, eventually leading to cell death. Iodine can also be antiviral, but the antiviral capacity of the parvovirus family is weaker than that of the enveloped virus. Iodine's antiviral mechanism may be to attack the protein in the viral envelope and destabilize it by reacting with the carbon-carbon double bond in the fatty acids in the envelope.

   
   (2)Iodine compound
    

       Oral iodide was used as a treatment for lead and mercury poisoning in the 19th and early 20th centuries before the discovery of organic chelating agents. Acute thyrotoxicosis can be treated with saturated solution of potassium iodide. It is also used to prevent iodine-131 from being absorbed by the thyroid gland.
    

       Iodine-131, a common component of radioactive fallout, is particularly dangerous because the thyroid collects ingested iodine-131 and leaves it there for a long time. Therefore, people at risk of being exposed to iodine-131 from radioactive fallout should always take iodine tablets containing iodine-127 (which is not radioactive). The dose for adults is one 130 mg iodine tablet every 24 hours, which provides 100 mg (100,000 micrograms) of iodine. (The daily intake is usually 100 micrograms.) Ingesting such a large dose of iodine-127 saturates the thyroid gland, minimizing the amount of iodine-131 absorbed by the thyroid gland.
    

       Iodine can absorb X-rays with energies below 33.3 keV due to its plateau suborder and electron density and the photoelectric effect of the innermost electrons. For this reason organoiodide compounds are commonly used as X-ray developers in angiography and CT scans. All water-soluble developers found so far contain iodine.

   
   4.Other Application
    

       A large proportion of iodine is used in the synthesis of the iodine additive for livestock feed. Another important use of iodine is as a catalyst for the synthesis of acetic acid by Cativa and Monsanto processes. In these acetic acid synthesis methods, the hydroiodic acid converts methanol into iodomethane, which carbonizes into acetyliodine, which then hydrolyzes into the product acetic acid, which forms hydroiodic acid.
    

       In the crystal rod process, iodine reacts with titanium, zirconium, hafnium, and thorium, and these metals are purified by the breakdown of iodide. Halogen lamps use a similar principle to extend the life of the bulb. Previous photographic films used silver iodide as a sensitive material. Tons of silver iodide are used every year for cloud seeding.

   
       Erythrin is an important food pigment. An iodine-containing bacteriostatic (AJ1629-34EC) can significantly inhibit the growth of Fusarium verticillioides, making it a potential alternative to less toxic antifungal agents.

   
       125I is used as a radioactive tracer to study which ligands bind to which plant pattern recognition receptors (PRRs). Mother liquor or antifreeze containing iodide ions can bind to protein crystals and provide phase information for X-ray diffraction.