What It Actually Is

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.