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The romance of 18th century chemical terminology

The Alchymist, In Search of the Philosopher's Stone, Discovers Phosphorus, and prays for the successful Conclusion of his operation, as was the custom of the Ancient Chymical Astrologers (Painting by Joseph Wright now in Derby Museum and Art Gallery, Derby, U.K.)

When Robert Boyle published The Skeptical Chymist in 1661, it marked the transition of the mystical tradition of alchemy to the science of chemistry. But the colorful names employed by the alchemists to describe their various concoctions lived on. The labels on the various retorts and flasks in an 18th century chemist's lab were redolent with occult associations, which did nothing to improve the public perception of the chemist.

The fanciful names are a thing of the past; for instance, you are unlikely to encounter "crocus of Mars" in a high school chem lab. A crocus was any solid of a reddish hue, named after the early blooming flower. Crocus of Mars was ferric oxide, named for the red planet. There was also an extract of Mars (ferric tartrate), Martial ethiops (black hydrated ferrosoferric oxide) and tincture of Mars, which was probably the same thing as lixiviate of Mars. To lixiviate was to extract soluble components of a solid mixture by repeated washing or percolation, in this case, iron salts.

If iron was a Martian element, lead belonged to Saturn. Crocus of Saturn was the name for lead oxide, also known as minium, or red lead. Lead acetate was called sal (salt) Saturni. Calcium acetate, on the other hand, was the salt of crab's eye.

A problem with 18th century terminology was that it emphasized the physical appearance of the chemical rather than its composition. The Venutian element was generally copper; thus Ens Veneris (Essence of Venus) was mixture of copper and ammonium chlorides. However, the same name was applied to a mixture of colcothar of green vitriol (ferric sulfate, also known as vitriol of Mars) with sal ammoniac (ammonium chloride) sublimed until it obtained a suitable Venutian yellow.

Similarly, Fuming Liquor of Libavious usually referred to a solution of stannic chloride, named for the 16th century chemist Andreas Libavius. However, his book Alchemia, published in 1597, contained instructions for the preparation of many strong acids, which could lead to confusion about which fuming liquid was the eponymous liquor.

The word vitriol comes from the Latin vitriolus or glassy, which was descriptive of various sulfates; in addition to green vitriol, there was white vitriol (zinc sulfate), blue vitriol (copper sulfate) also known as the vitriol of Venus, as well as the vitriol of Jove (stannous sulfate). Sulfuric acid came to be known as simply vitriol, from which we get the word for bitter or abusive speech. Hydrochloric acid was sometimes called the philosophical spirit of vitriol.

Phlogiston was a mythical element thought to impart the property of inflammability, the descendant of the classical element of fire. A substance could no longer burn when it ran out of phlogiston, which was absorbed by air during the process of combustion. Air, on the other hand, could only absorb so much phlogiston. Pure oxygen was said to be dephlogisticated, since it could absorb the most phlogiston. Hydrogen gas, on the other hand, was thought by its discoverer, Henry Cavendish to be pure phlogiston, or as he called it "inflammable air." 

Salt Alembroth was also known as the salt of wisdom of salt of science. A mixture of mercuric chloride and ammonium chloride, it was used to purify metals, a major goal of the alchemists, along with their holy grail, the transmutation of base metals to gold.

Sal mirabilis was so named by its discoverer, Johann Rudolf Glauber, because of its wondrous medicinal properties.  Also known as the cathartic salt of Glauber, Na2SO4·10H2O is a very effective laxative. The natural mineral is still called mirabilite. 

A more violent purgative was pulvis angelicus (angel dust), also known as the powder of Algaroth or mercurius vitae. It was prepared by mixing butter of antimony (antimony trichloride) with water to make antimonious oxychloride.

Some of the cultural history of chemistry has been lost with the passing of its wonderful terms into history; "angel dust" seems a much more culturally resonant term than "antimonious oxychloride." It was, in essence, a kind of early trade name for a particular pharmacologic product. On the other hand, "angel dust" today is also a street-name for phencyclidine (PCP), a powerful hallucinogenic, dissociative drug. "Antimonius oxychloride" has the advantage of specificity.

Another lesson to be learned from these 18th century terms is that nomenclature dies hard, which is certainly a problem when it has occult significations. Alchemists were widely reviled as charlatans and con artists, and some were actually executed. In his Divine Comedy, Dante consigned them to the eight circle of Hell, which was way down there. Ben Jonson's 1610 play, The Alchemist, concerned a fraudster named Subtle who made false promises to his victims. Chaucer's The Yeoman's Tale recounted the history of a sleazy alchemist, including the famous couplet:

                But al thyng which that shineth as the gold
                Nis nat gold, as that I have herd it told;

True chemists, the successors to Robert Boyle, had to struggle hard to attain respectability with the general public.

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Ancient practice of alchemy can be replicated in today's lab



Steven A. Edwards, Ph.D.

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