Zinc

Zinc has a long and geographically split history: it was smelted as a distinct metal in India, at Zawar in Rajasthan, from around the twelfth century and in China not long after, while in Europe it was recognised as a separate element only in the eighteenth century, notably through the work of Andreas Marggraf around 1746. Its brass alloy with copper, however, had been made for thousands of years before the pure metal was understood.

The name probably derives from the German Zinke, a prong or tooth, describing the shape of the crystals that form on cooling. A bluish-white metal, zinc is used above all to galvanise steel against rust, and in brass, die-cast alloys and batteries, while it is also an essential trace element, required by hundreds of enzymes in the human body. Zinc deficiency was recognised as a distinct nutritional problem only in the 1960s, through studies of stunted growth in rural Egypt and Iran, a relatively late scientific discovery for so essential a trace element. Zinc lozenges and nasal sprays marketed to shorten the common cold sit in more contested territory: clinical trial evidence remains mixed and inconsistent, and the FDA warned in 2009 that one zinc nasal product could cause permanent loss of smell, a caution against treating a genuine nutrient as an unqualified cure-all. Ancient Indian metallurgical and alchemical texts, including the Rasaratna Samuccaya, describe jasada, zinc, among the processed metals of Ayurvedic medicine centuries before European chemists recognised it as a distinct element.

Zinc occupies an ambiguous place in the Western tradition: it was never one of the seven planetary metals of classical alchemy, because it was not clearly recognised as a metal in Europe until late, yet it entered the alchemical literature all the same. Paracelsus, in the sixteenth century, wrote of zincum as a distinct metal, and the white flowers of zinc oxide that rose during its burning were named lana philosophica, philosopher's wool, a poetic term of the laboratory. Zinc thus sits at the edge of alchemy, acknowledged by its later practitioners but excluded from the ancient planetary scheme, a metal known in its compounds and its brass long before it was won and named in its own right.

Zinc oxide has its own long pharmaceutical afterlife in calamine lotion, still sold today for skin irritation, its name drawn from the same calamine ore that also yielded Stromeyer's cadmium. Because reliable brass, a true copper-zinc alloy, seems not to have been deliberately smelted in the Mediterranean world until Hellenistic and Roman times, when it was called orichalcum, most instances of brass in older English Bible translations are understood by scholars to render Hebrew or Greek words for bronze or unspecified yellow metal rather than the zinc alloy in the modern sense, a nuance that leaves zinc itself, unlike copper or iron, essentially absent from scriptural chemistry.