English: III. CLAVIS, the third key, engraved by Matthaeus Merian (1593–1650). From Tripus aureus, hoc est, Tres tractatus chymici selectissimi, nempe I. Basilii Valentini, benedictini ordinis monachi, Germani, practica una cum 12. clavibus et appendice, ex germanico; II. Thomae Nortoni, angli philosophi crede mihi seu ordinale, ante annos 140. ab authore seriptum, nunc ex anglicano manuscripto in latinum translatum, phrasi eujusque authoris ut et sententia retenta; III. Cremeri cuiusdam abbatis westmonasteriensis angli testamentum, hactenus nondum publicatum, nunc in diversarum nationum gratiam editi, et figuris cupro affabre incisis ornati operâ et studio. Michaelis Maieri, phil. et med. d. com. p. &c. Francofurti, apud Hermannum à Sande. MDCLXXVII. as published in the collection Musaeum hermeticum, reformatum et amplificatum. Francofurti : Apud Hermannum à Sande, 1678. In Latin.

The part in question 'I. Basilii Valentini, benedictini ordinis monachi, Germani, practica una cum 12. clavibus et appendice, ex germanico;' or 'Basil Valentine, a German monk of the Benedictine order, one study with the twelve keys and the appendix, [translated] from the German.'

Basil Valentine in his writings provided twelve “keys,” a widely reproduced sequence of alchemical operations encoded allegorically, both in words and in images. The images were essential to the communication and had to depict the same scene, regardless of the artistry.

The third of Basil Valentine’s keys shows a winged dragon with coiled tail and pointed tongue in the foreground of a landscape with high mountains and a city or castle in the background. On the left behind the dragon is a running wolf or fox with a bird in its mouth. The fox, in turn, is being attacked by a cockerel on its back: a rooster is eating a fox eating a rooster.

What could this possibly symbolize? Lawrence Principe, professor of chemistry and history of science at Johns Hopkins University, has discovered the surprising answer along with an equally surprising chemical sophistication. The rooster symbolizes gold (from its association with sunrise and the sun’s association with gold), and the fox represents aqua regia, a combination of nitric and hydrochloric acid that dissolves gold. The repetitive dissolving, heating, and redissolving (the rooster eating the fox eating the rooster) leads to the buildup of chlorine gas in the flask. The gold then volatilizes in the form of gold chloride, whose red crystals were known as dragon’s blood. The reaction was not reported in modern chemical literature until 1890.