Often, when Saltpeter is involved, a Salamander is in the nearby. Here Lemery gives an insight on the ways to work what Fulcanelli called Stable Salt.
Together with a deep insight on the way chemicals were produced in seventeenth century. Consequently with an interesting similitude with alchemical processes in preliminary works to volatilize salt. If you are not interested in Saltpeter per se, know that this part is also an essential to get to the ancient processes to obtain Aqua Regia.
Sometimes used to decrease melting temperatures, sometimes helpful to raise loader metallic substances, sometimes naturally rich in Secret Fire/Mercurius, Saltpeter is very often mentioned in Alchemy.
The Lemery end products, that’s to say purified Saltpeter, Salt de Prunelle, Salt Polichreste, Strong Water, fixation in Alkali, are basically different from those made in modern laboratory. Unlikely my two previous posts on the Glaser’s trainee, namely Lemery and the Spirits of Salt Armoniac and Lemery & the Spirits of Common Salt with Wine, here the reader should read more between the lines, since these proceedings are less consequent. As well as more in a whole, in fact I decided to unify the work on Saltpeter in a single long article.
The reading of the aforementioned articles, is quite essential to better understand this part, sparing me, and the foregoing readers, the repetition of the same concepts.
Nicolas Lemery, Cours de Chimie, Chapter XV or fifteenth, On Nitre or Saltpeter, page 283, my translation from original french: “Nitre is a salt saturated with an amount of the Spirit of Air which makes it volatile, it can be extracted from the stones and earths obtained during the processes of ships demolishing. It is also found in mines, and in other humid places, caused by the Air condensation and it tends to bind to stones.
Page 284: Saltpeter is also sometimes procured from animal urine falling on stones and earths; someone has even thought all the Saltpeter coming from there, but we can see every day that it is extracted from places which have nothing to do with urine. This salt is half volatile and half simile to rock salt, as we will see later.
Saltpeter is not easily inflammable, as believed by most of chemists; but when it finds some sulphur in a fire, it tends to join and help to raise the volatile part; in a way it serves as a vehicle.
Or in the case it is thrown on some sulphur with coal, Saltpeter will produce a considerable flame, on the contrary inside a red hot crucible it will not burn at all because it will not find any sulphur.
Page 285, Purification of Saltpeter: Have ten or twelve pounds of Saltpeter in a adequate amount of water, let the dissolution to set and then filter it, then make it evaporated in a glass or earthen platter till half reduction or at least till it will appear as having a thin layer covering surface. So bring your platter in a cold place, the less possible agitating it, and let it over night. You will find some crystals which must be removed from the liquor, then make this liquor to evaporate again till the layer formation and bring it again in a cold place. You will find crystals again: go over with evaporations and crystallizations till you will have extracted all the Saltpeter. Note that during the last crystallizations you will have a salt all comparable to the sea salt, or rock salt, which has to be put aside to be served in particular eating. The first obtained crystals are those of purified Saltpeter. You may dissolve and purify the Saltpeter over and over in the water, and you can see every time all we have said about its purification from he sea salt.”
What’s roughly the difference between that kind of chemical salt volatilization and an alchemical one ( since our Mercurius is extracted by means of salts volatilization)? In Alchemy volatilizations must be performed in closed conditions, in order not to miss anything. Chemical volatilizations in open air are generic achievement of crystals, of Saltpeter of course, but Alchemy is something more than a mere purification of Saltpeter and separation from the other salts.
Notes: The first Saltpeter purification to be done is the following. Roughly powder the stones and earths containing it: then make the whole boiling in a large volume of water to dissolve the Saltpeter. Cool down the dissolution, then pour it on some ashes to make a lixiviation and in so doing remove any greasy substance, then pass again the liquor over the ashes, and let the whole evaporate and crystallize.