Argol

Argol is the crude, crystalline form of alum, primarily consisting of potassium aluminum sulfate dodecahydrate (KAl(SO4)2·12H2O). It forms as a crust or delicate crystals on the surface of concentrated alum solutions as they evaporate and cool. The term has historical usage in chemistry and pharmacology, often referring to the impure crystals that precede refining alum. Argol crystals typically contain small amounts of impurities such as other metallic salts and residual solution.

Production and characteristics: In the production of alum, a saturated solution is evaporated and allowed to crystallize. The first, crude crystals that appear on the surface are called argol. It is then separated, washed, and dried to yield the purer alum used for various applications. Because argol is a crude product, it may carry traces of other substances and moisture, affecting its appearance and reactivity compared with fully refined alum.

Uses and historical context: Historically, argol was used as an astringent in medical preparations and as a coagulant for clarifying wines, fruit juices, and other beverages. It also served as a mordant in dyeing and as a component in tanning processes. In modern chemistry and industry, the refined compound is more commonly employed, while argol remains of interest largely for historical, archival, or traditional manufacturing contexts.

Etymology and scope: The name argol derives from older European terminology for crystallized alum. Today, argol is mainly encountered in historical texts and in discussions of traditional alum production, while the standard reference material for most applications is the purified alum.