ALKACHEST, or Alcahest, in Chemistry, a universal Menstruum or Dissolvent, wherewith some Chemists have pretended to resolve all Bodies into their first Matter. See MENSTRUUM, DISSOLVENT, MATTER, &c. Those two eminent Adepts, Paracelsus and Helmont, expressly declare, that there is a certain Fluid in Nature, capable of reducing all sublunary Bodies, as well homogeneous as mixed, into their Ens principii, or Original Matter whereof they are composed; or into an uniform equable and potable Liquor, that will unite with Water and the Juices of our Bodies, yet retain its seminal Virtues; and if mixed with itself again, thereby be converted into pure elementary Water.—Whence they also imagined, it would at length reduce all Things into Water. See WATER. This Declaration, seconded by the Affirmation of Helmont, who religiously swears himself possessed of the Secret, has excited the succeeding Chemists and Alchemists to the Pursuit of so noble a Menstruum. Mr. Boyle was so fond of it, that he frankly acknowledges he had rather have been Master thereof than of the Philosopher’s Stone. See ALCHEMY.

Indeed, ’tis not difficult to conceive, that all Bodies might originally arise from some first Matter, which was once in a fluid Form.—Thus, the primitive Matter of Gold is, perhaps, nothing more than a ponderous Fluid, which from its own Nature or a strong Attraction between its Parts, afterwards acquires a solid Form. See GOLD. And hence, there does not appear any Absurdity in the Notion of a universal Menstruum, that resolves all Bodies into their Ens genitale.

The Alkahest is a Subject that has been canvassed by an infinite Number of Authors; as, Paracelsus, Philalethes, Tachenius, Ludovicus, &c.—— Boerhaave says, a Library might be collected out of them. Weidenfelt, in his Treatise de Secretis Adeptorum, has given us all the Opinions that have been entertained about it. The Term Alkahest is not peculiarly found in any Language: Helmont declares he first observed it in Paracelsus, as a Word that was unknown before the Time of that Author, who in his second Book, De viribus Membrorum, treating of the Liver, has these Words: Eft etiam Alkahett liquor, magnam hepatis conservandi & confortandi, &c.

“There is also the Liquor Alkahest, of great efficacy in preserving the Liver; as also in curing hydropical and all other Diseases arising from Disorders of that Part.

If it have once conquered its like, it becomes superior to all other hepatic Medicines; and though the Liver itself were broken and dissolved, this Medicine should supply its Place,” 'Tis this single Passage of Paracelsus, that excited the succeeding Chemists to an Inquiry after the Alkahest; there being but one other indirect Expression about it in all his Works.

Now it being a frequent Practice with this Author to transpose the Letters of his Words, and to make use of Abbreviations, and other ways of Concealment; as in Tartar, which he would write Sutratar; for Nitrum, Mutrin, &c. 'tis supposed Alkahest is such a Word thus disguis'd. Hence some imagine it formed of Alkali est; and accordingly, that it was the Alkaline Salt of Tartar volatilized. This seems to have been Glauber’s Opinion; who indeed performed surprising things with such a Menstruum upon Subjects of all the three Kingdoms. Others will have it the German Word Algeist, q. d. wholly spirituous, or volatile; Others are of Opinion, that Alkahest is taken from Salis-geist, which signifies Spirit of Salt; for the Universal Menstruum, 'tis said, is to be wrought from Water; and Paracelsus himself calls Salt the Centre of Water, wherein Metals ought to die. So—In effect, Spirit of Salt was the great Menstruum he used on most Occasions. The Commentator on Paracelsus, who gave a Latin Edition of his Works at Delft, assures that the Alkahest was Mercury, converted into a Spirit. Zwelfer judged it to be a Spirit of Vinegar rectified from Verdigrease. And Starkey thought he discovered it in his Soap.

There have been some synonymous and more significant Words used for the Alkahest. The elder Helmont mentions the Alkahest by the compound Name of Ignis-aqua, Fire-Water: But he here seems to mean the circulated Liquor of Paracelsus; which he terms Fire, from its Property of consuming all things; and Water, on account of its liquid form. The same Author calls it Ignis-gehennae, infernal Fire; a Word also used by Paracelsus: He also intitles it Suavum & felicissimum omnium salium, the principal and most successful among Salts, which having obtained the highest degree of Simplicity, Purity, and Subtility, alone enjoys the Faculty of remaining unchanged and unimpaired by the Subjects it works on, and of dissolving the most stubborn and untractable Bodies, as Stones, Gems, Glass, Earth, Sulphur, Metals, etc., into real Salt, equal in weight to the Matter dissolved; and this with as much ease as hot Water melts down Snow. This Salt, continues he, by being several times cohobated with Paracelsus Sal circulatus, loses all its Fixedness; and at length becomes an insipid Water, equal in quantity to the Salt it was made from. Helmont is express that this Menstruum is entirely the Product of Art, and not of Nature. Though, says he, a homogeneal Part of elementary Earth may be artificially converted into Water, yet I deny that the same can be done by Nature alone; for no natural Agent is able to transmute one Element into another. And this he offers as a Reason why the Elements always remain the same. It may set some light into this Affair, to observe that Helmont, as well as Paracelsus, took Water for the universal Instrument of Chemistry, and Natural Philosophy; and Earth for the unchangeable Basis of all Things: That Fire was designed as the efficient Cause of all Things; that seminal Impressions were lodged in the Mechanism of Earth; and that Water, by dissolving and fermenting with this Earth, as it does by means of Fire, brings everything to light; whence originally proceeded the Animal, Vegetable, and Mineral Kingdoms; even Man himself being thus at first created, agreeably to the account of Moses. The great Character or Property of the Alkahest, we have observed, is to dissolve, and change all sublunary Bodies; Water alone excepted. The Changes it induces proceed thus: 1°, The Subject exposed to its Operation, is converted into its three Principles, Salt, Sulphur, and Mercury; afterwards, into Salt alone; which then becomes volatile; and at length is wholly turned into insipid Water. The manner of Application is by touching the Body proposed to be dissolved, e.g., Gold, Mercury, Sand, or the like, once or twice with the pretended Alkahest; and if the Liquor be genuine, the Body will be converted into its own Quantity of Salt.

2°, It does not destroy the seminal Virtues of the Bodies dissolved thereby—Thus, Gold is, by its Action, reduced to a Salt of Gold; Antimony to a Salt of Antimony; Saffron to a Salt of Saffron, etc., of the same seminal Virtues, or Characters with the original Concrete. By seminal Virtues, Helmont understands those Virtues which depend upon the Construction or Mechanism of a Body, and make it what it is. Hence, an actual and genuine Aurum potabile might readily be gained by the Alkahest, as converting the whole Body of Gold into a Salt, retaining its seminal Virtues, and being withal soluble in Water.

3°, Whatever it dissolves, may be rendered volatile by a Sand-heat; and if after volatilizing the Solvend, it be distilled therefrom, the Body is left pure insipid Water, equal in quantity to its original self, but deprived of its seminal Virtues. Thus, if Gold be dissolved by the Alkahest, the Metal first becomes Salt, which is potable Gold; but when the Menstruum is distilled therefrom, it's left mere Elementary Water. Whence it appears, that pure Water is the last Production or Effect of the Alkahest.

4°, It suffers no Change or Diminution of Force by dissolving the Bodies it works on, and therefore sustains no Reaction from them; being the only immutable Menstruum in Nature.

5°, "Tis incapable of Mixture, and therefore remains free from Fermentation and Putrefaction; coming off as pure from the Body it has dissolved, as when first put thereon; without leaving the least Foulness behind.