Ammonium chloride

Overview
Ammonium chloride (NH4Cl) (also Sal Ammoniac, salmiac, nushadir salt, zalmiak, sal armagnac, sal armoniac, salmiakki, salmiak and salt armoniack) is, in its pure form, a clear white water-soluble crystalline salt of ammonia. The aqueous ammonium chloride solution is mildly acidic.

History
The modern name "ammonium" comes from sal ammoniac. The substance was known as nushadir salt (Arabic and Persian: نشادر) in Arabic-speaking countries and Persia, naosha in China, nao sadar in India. The Romans called the ammonium chloride deposits they collected from near the Temple of Jupiter Amun (Greek Ἄμμων Ammon) in ancient Libya 'sal ammoniacus' (salt of Amun) because of proximity to the nearby temple.

It was considered one of the four alchemical "spirits". While the way that it dissociates into two corrosive materials (ammonia and hydrochloric acid) which attack metals convinced some eager alchemists that it might hold the key to converting one metal to another, Arabs used it as a source of ammonia:


 * 2NH4Cl + 2CaO → CaCl2 + Ca(OH)2 + 2NH3

Applications
Ammonium chloride is sold in blocks at hardware stores for use in cleaning the tip of a soldering iron and can also be included in solder as flux.

Other uses include a feed supplement for cattle, in hair shampoo, in textile printing, in the glue that bonds plywood, as an ingredient in nutritive media for yeast, in cleaning products, and as cough medicine. Its expectorant action is caused by irritative action on the bronchial mucosa. This causes the production of excess respiratory tract fluid which presumably is easier to cough up. It is also used in an oral acid loading test to diagnose distal renal tubular acidosis.

Ammonium chloride is used in snow treatment, namely on ski slopes at temperatures above 0 °C, to harden the snow and slow its melting.

In several countries sal ammoniac is used to spice up liquorice-type dark candies (Finland's salmiakki, Sweden's lakrisal, the Netherlands' zoute drop and the Danish Dracula Piller are popular examples), and as a flavoring for vodkas.

Ammonium chloride is used as an expectorant, diuretic and systemic acidifying agent. It is used in the treatment of severe metabolic alkalosis, to maintain the urine at an acid pH in the treatment of some urinary-tract disorders or in forced acid diuresis.

Ammonium salts are an irritant to the gastric mucosa and may induce nausea and vomiting.