Ammonium iodide

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Ammonium iodide

Ammonium iodide is an inorganic compound with the chemical formula NH4I. It is used in photographic chemicals and some medications. It can be prepared by the action of hydroiodic acid on ammonia. This white crystalline salt is a significant material in the field of chemistry and has various applications in the pharmaceutical industry and in photographic processes.

Properties

Ammonium iodide is a white crystalline solid that is highly soluble in water. It decomposes upon exposure to light, gradually turning yellow as it releases iodine. This property is significant in its application in photography, where it is used in the formulation of silver iodide for photographic films. The compound has a melting point of 551°C and a boiling point where it decomposes.

Synthesis

Ammonium iodide can be synthesized by directly combining aqueous solutions of ammonium hydroxide (NH4OH) with hydroiodic acid (HI), according to the equation:

\[ NH_4OH + HI \rightarrow NH_4I + H_2O \]

This reaction produces ammonium iodide and water. The product can be purified by recrystallization from water.

Applications

1. 1. 1. Photography

In photography, ammonium iodide is used to prepare emulsions of silver iodide, which are sensitive to light and essential for the development of photographic films and papers.

1. 1. 1. Medicine

Ammonium iodide has been used in some cough medicines as an expectorant, although its use is less common today due to the availability of more effective and safer alternatives.

1. 1. 1. Chemical Synthesis

It serves as a source of iodide in organic synthesis, where it can be used to introduce iodide ions into reactions, facilitating various chemical transformations.

Safety

Ammonium iodide should be handled with care, as it is harmful if swallowed and causes irritation to the skin, eyes, and respiratory tract. Appropriate safety measures, including the use of personal protective equipment, should be taken when handling this chemical.

See Also

• Ammonium chloride
• Ammonium bromide
• Silver iodide
• Photographic film