Nao Sha

Nao Sha, sal ammoniac, is a naturally occurring or refined mineral substance composed of ammonium chloride (NH4Cl). It crystallises in the isometric system as colourless to white, sometimes yellow- or grey-tinted cubes or fibrous aggregates, often found near volcanic fumaroles and burning coal seams. The drug has a sharp, salty, biting taste and is highly soluble in water. In classical TCM it is described as salty, bitter, acrid, and warm with toxicity, and was used to soften hardness, disperse accumulations, transform phlegm, eliminate damp, and expel parasites; topical applications include corrosive treatment of warts, fixed masses, and chronic ulcerations. Owing to potential mucosal irritation, gastrointestinal toxicity, and risk in patients with renal or hepatic impairment, modern Chinese practice discourages internal use and reserves it for carefully controlled external preparations.