Tria prima: sulphur, mercury and salt
Sulphur, mercury and salt: the three principles that Paracelsus, the sixteenth-century physician, held every substance to be made of. Sulphur was what burns, mercury what is fluid and changeable, salt what stays solid. Alchemists wrote them with a triangle on a cross, Mercury’s horned sign and a circle cut across by a line.
Meaning
Tria prima is Latin for “three primes”. They are principles, not the substances sold under those names: John Henry Pepper wrote in 1861 that Geber’s mercury and sulphur were not the real substances but imaginary and theoretical principles. The medieval Arab alchemist Jābir ibn Hayyān (Geber in Latin) had added sulphur and mercury to the four classical elements; Paracelsus added salt as a third, a commentary on the University of Oxford’s Cabinet explains. He showed it by burning a piece of wood: the flame was the work of sulphur, the smoke of mercury, and the ash left behind of salt. The three are part of the history of chemistry now, and of the alchemical signs, which the Indiana University historians of Newton’s alchemy say are still in use in scholarly literature and in New Age texts.
Origin and history
The pair came first. The 1911 Encyclopædia Britannica sums up the medieval doctrine that the metals are composed of mercury and sulphur. Paracelsus (about 1490–1541), whom the same Britannica calls the famous German physician of the sixteenth century, made the pair three. A short treatise in his collected works, “Concerning the Three Prime Essences” in A. E. Waite’s translation of 1894, opens: “Every thing which is generated and produced of its elements is divided into three, namely, into Salt, Sulphur, Mercury.” It gives each a form: liquor is the form of mercury, oiliness of sulphur, alkali of salt. Waite’s note calls the doctrine the foundation of Paracelsus’s physics and philosophy, and the treatise uses it to explain the origin of diseases. The works attributed to Basil Valentine also hold sulphur, mercury and salt to be the constituents of the metals.
Body, spirit and soul
Paracelsus applied the three to people too. In the Oxford commentary’s summary, salt corresponded to the body, mercury to the spirit (the seat of imagination, moral judgement and the higher mental faculties) and sulphur to the soul (the seat of the emotions and desires). The same three, body, spirit and soul, are the triangle in Michael Maier’s emblem of the philosopher’s stone.
Three principles beside four elements
The tria prima did not replace the four elements of Aristotle. The Oxford commentary says they coexisted and competed with them in Paracelsian alchemy, and it reproduces a figure that puts both in one picture: a triangle whose corners are soul, spirit and body, a square whose corners hold the signs of fire, air, water and earth, and a seven-pointed star with the signs of the seven planets. The elements’ triangles are on the page for the four elements.
The three signs
The symbol guide to Newton’s alchemical papers gives the three signs: a triangle standing on a cross for sulphur, the sign of the planet Mercury for mercury, and a circle with a line across it for salt. The editors of the Chymistry of Isaac Newton add a rule for reading Newton’s own compound signs: in general, a horizontal line through a circle may be taken to mean a salt. When the Indiana historians proposed the alchemical signs for Unicode in 2009, they set the salt sign apart from the look-alike Unicode character circled minus, and placed the salts next to the signs for sulphur and mercury because salts were so important to Paracelsus.
Boyle’s doubts
In The Sceptical Chemist (1661) Robert Boyle, himself an alchemist, doubted the experiments by which “vulgar Spagyrists” tried to prove salt, sulphur and mercury the true principles of things, and moved towards elements as what matter cannot be broken down into further, Britannica writes. J. J. Becher later swapped the three for three earths, the mercurial, the vitreous and the combustible.
Read next
- Next in Occult and alchemical symbolsPhilosopher’s stone (squared circle)The philosopher’s stone was the substance alchemists sought for turning base metals into gold or silver. Its best-known emblem is the squared circle of Michael Maier: a circle inside a square, inside a triangle, inside a circle.
- Paracelsus’s three principles stood beside the four elements, whose triangles alchemy drewThe four elementsEarth, air, fire and water, with spirit often added as a fifth. Wiccans set a tool on the altar for each, and write the elements as triangles: fire pointing up, water pointing down, and air and earth the same, each crossed by a bar.
See also
Planetary metals (☉ ☽ ☿ ♀ ♂ ♃ ♄), Ouroboros, Pentagram, Baphomet.
Sources
- Alchemy, the Four Elements, and the Tria Prima, Commentary, SS 14: The Scientific Movement of the 17th Century (Internet Archive copy, April 2026), Cabinet, University of Oxford, Images 1 and 2
- The Hermetic and Alchemical Writings of Paracelsus, vol. 1, translated by A. E. Waite (1894); Cornell University Library copy, James Elliott and Co., London (scan on the Internet Archive), Appendix I, “Concerning the Three Prime Essences”, ch. 1, p. 317
- Alchemy, Encyclopædia Britannica, 11th edition (1911), vol. 1, Wikisource, Mercury and sulphur; later alchemy
- Atalanta fugiens, Emblem 21: “Of the Secrets of Nature”, Michael Maier; 17th-century English translation in the digital edition, Furnace and Fugue (Brown University Digital Publications), Emblem 21: discourse (English)
- Paracelsus, Encyclopædia Britannica, 11th edition (1911), vol. 20, Wikisource, Opening
- Symbol Guide, The Chymistry of Isaac Newton, general editor William R. Newman, Indiana University, Introduction; term list
- Proposal for Alchemical Symbols in Unicode, William R. Newman, John A. Walsh, Stacy Kowalczyk and Wallace E. Hooper, 26 January 2009 (Unicode document L2/09-037), Indiana University, for the Unicode Technical Committee (unicode.org), pp. 4–5
- The Playbook of Metals, by John Henry Pepper, 1861 (scan on the Internet Archive), Routledge, Warne and Routledge, London, p. 128
The same shape elsewhere
Browse symbols formed from circles, crosses or triangles.
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 10, 2026. How we research
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