Sal Ammoniac

Sal Ammoniac was known from antiquity as a natural sublimate collected from the soot of burning camel dung near certain Egyptian sites associated with the god Amun, whose Latinized name may lie behind the word ammonia itself, though that etymology is debated. By the medieval period it was manufactured deliberately across the Islamic world and later Europe by subliming soot, urine salts, and other nitrogenous animal waste in closed vessels, collecting the white crystalline sublimate that condensed on the vessel's cooler upper surface. It dissolves readily in water with a marked cooling effect, sublimes cleanly when heated without passing through a liquid phase, and reacts with many metal salts to form new volatile compounds, all properties that made it one of the most used reagents in the alchemical workshop.

Metalworkers used it as a flux for soldering, since it cleans oxide films from metal surfaces at soldering temperatures; dyers and textile workers used it as a mordant; and alchemists used it constantly in combination with corrosive sublimate (mercuric chloride) and other salts to make compound preparations such as sal alembroth. Its sharp, ammoniacal smell and its habit of vanishing entirely into vapor on gentle heat, leaving no visible residue unless a metal salt were combined with it, gave it a reputation as an unusually spiritual, volatile salt, one that seemed to carry an active principle rather than sitting inert like common salt.

The sal ammoniac of later medieval and early modern Europe is identified with confidence as ammonium chloride, NH4Cl, a straightforward and stable compound whose sublimation behavior matches the historical descriptions closely. The harder question is the older Arabic nushadir, attested from around the eighth to tenth centuries in the Jabirian corpus and other early alchemical writing; historians including Lawrence Principe treat the continuity between nushadir and the later European sal ammoniac as probable but not textually certain in every instance, since medieval translators and compilers sometimes applied a familiar Latin name to a substance description that does not perfectly match its later namesake, and some early recipes for nushadir describe sources and properties that fit ammonium chloride only loosely.

The safest statement, and the one this entry follows, is that sal ammoniac names a family of related volatile ammonium salts across a very long period, with ammonium chloride as the specific, well confirmed identity from about the thirteenth century forward, and a probable but not certain identity for the substance under its earlier Arabic name. Readers encountering the bare word sal ammoniac in a translated medieval source should treat the modern formula given here as the best available reading for that later period rather than as a settled fact reaching all the way back to the word's earliest recorded use.