It is obvious that this narrative is a complete mystification, and that either the stranger was a myth or Helvetius was the victim of a deception.
The recipes that the alchemists formulate--those, that is, who profess to have discovered the stone, or to have known somebody who enjoyed so rare a fortune--are always unintelligible or impracticable. What is to be understood, for example, of the following elaborate process, or series of processes, which are recorded by Mangetus, in his preface to the ponderous 'Bibliotheca Chemica' (to which reference has already been made)?
1. Prepare a quantity of spirits of wine, so free from water as to be wholly combustible, and so volatile that a drop of it, if let fall, will evaporate before it reaches the ground. This constitutes the first menstruum.
2. Take pure mercury, revived in the usual manner from cinnabar; put it into a glass vessel with common salt and distilled vinegar; shake violently, and when the vinegar turns black, pour it off, and add fresh vinegar. Shake again, and continue these repeated shakings and additions until the mercury no longer turns the vinegar black; the mercury will then be quite pure and very brilliant.
3. Take of this mercury four parts; of sublimed mercury (_mercurii meteoresati_--probably corrosive sublimate), prepared with your own hands, eight parts; triturate them together in a wooden mortar with a wooden pestle, till all the grains of running mercury disappear. (This process is truly described as 'tedious and rather difficult.')
4. The mixture thus prepared is to be put into a sand-bath, and exposed to a subliming heat, which is to be gradually increased until the whole sublimes. Collect the sublimed matter, put it again into the sand-bath, and sublime a second time; this process must be repeated five times. The product is a very sweet crystallized sublimate, constituting the _sal sapientum_, or wise men's salt (probably calomel), and possessing wonderful properties.
5. Grind it in a wooden mortar, reducing it to powder; put this powder into a glass retort, and pour upon it the spirit of wine (see No. 1) till it stands about three finger-breadths above the powder. Seal the retort hermetically, and expose it to a very gentle heat for seventy-four hours, shaking it several times a day; then distil with a gentle heat, and the spirit of wine will pass over, together with spirit of mercury. Keep this liquid in a well-stoppered bottle, lest it should evaporate. More spirit of wine is to be poured upon the residual salt, and after digestion must be distilled off, as before; and this operation must be repeated until all the salt is dissolved and given off with the spirit of wine. A great work will then have been accomplished! For the mercury, having to some extent been rendered volatile, will gradually become fit to receive the tincture of gold and silver. Now return thanks to God, who has hitherto crowned your wonderful work with success. Nor is this wonderful work enveloped in Cimmerian darkness; it is clearer than the sun, though preceding writers have sought to impose upon us with parables, hieroglyphs, fables, and enigmas.