White Vitriol

White Vitriol was gathered as colorless to faintly yellow or greenish crystalline crusts on weathered zinc ore, most notably from the Rammelsberg mines near Goslar, whose vitriol works supplied much of central Europe from the Middle Ages onward. Unlike green and blue vitriol, which were tied to well recognized metals, white vitriol's parent metal was for centuries poorly understood; European metallurgists knew zinc mainly as an ingredient of brass and calamine and did not isolate it reliably as a pure metal until the sixteenth century in India and the eighteenth in Europe, so white vitriol was for a long time simply the vitriol that is not green or blue, identified by its color and taste rather than by its metal. It was used in medicine as an astringent styptic to stop bleeding and, in stronger doses, as an emetic, and later in dyeing and as a mordant.

As with the other vitriols, roasting and distilling white vitriol yielded a share of the acid spirit that chymists collected as oil of vitriol, though green vitriol remained the preferred feedstock for that operation since it was far more abundant. White vitriol's zinc content also meant that when it was included in metallic reduction experiments, the regulus recovered was a metal early chemists struggled to classify at all, sometimes calling it a bastard or false metal rather than admitting an eighth true metal alongside the seven of the planets.

White Vitriol is zinc sulfate heptahydrate, ZnSO4.7H2O, structurally almost identical to green vitriol (iron) and blue vitriol (copper), the three forming a natural family of hydrated divalent metal sulfates that early modern chemists began to recognize as a family well before they understood why the pattern held. The identification is secure and uncontested for the color qualified name; historians of chemistry such as Lawrence Principe treat the qualified vitriols, unlike the bare unqualified word, as reliably mapping onto a single modern compound once the color is specified.

What is more historically interesting than the chemistry is the metal underneath it: zinc's slow recognition as a distinct element, rather than a variant or impurity of other metals, meant that white vitriol was chemically characterized and used in commerce for centuries before anyone could have named the metal it actually contained, a reminder that alchemical and early chemical classification tracked substances by observable behavior long before it could ground that behavior in elemental composition. The parallel with calamine, another zinc material whose recognition as a zinc substance lagged well behind its practical use, is not a coincidence: zinc's late isolation as a distinct metal is exactly why both white vitriol and calamine kept descriptive, place based or color based names for so long instead of a name built on the metal itself.