Page 287 : the same earth which has been cleaned from Saltpeter can be place again in the Air and again discharged from Saltpeter, provide you let the necessary time this earth be again impregnated by Saltpeter.
The oblong crystals in which this salt can appear come from its volatile part, since this being the last part to be crystallized and fixed just like the sea salt whose it takes the shape. Saltpeter cannot be proficiently refined if it doesn’t contain a certain amount of a salt similar to rock salt, or sea salt, in within. But in less quantity than before.
When Saltpeter is being boiled at the utmost temperatures for a long time, a part of Spirits get dissipated and in the end it remains a salt similar the sea salt, or rock salt. That’s proving the Saltpeter is nothing more than a rock salt more impregnated with Spirits than the first one, as we have said when talking of principles.”
Along with the possibility of hygroscopic salts to retain some qualities from air, in addition to water or even contained inside water, and here I’m talking of that Mercurius Universalis coming from Sun and Moon and hovering in the Air (1), what jumps to a trained eye is here the absolute Lemery’s disregard to every molecular purity. Note the same absence of interest among alchemists.
“Page 288: When one wants to have some salt crystallized, this must be dissolved in a suitable volume of water, since if it was excessive, the would cause the be to much weak and unable to coagulate; and if on the contrary the water was less than suitable the crystals would be very poorly shaped. So to make them conformed, one has to remove the platter from fire, when you can see the thin layer to appear above the liquor, this being a sign there is a little less moisture to keep the salt in dissolution and so when put in a cool place there’s no lack of fixation. and among those the volatile ones, get crystallized in less time than the others.
The Saltpeter gets frozen since being acid it burdens fluids which because of their too intense agitation seize and make them precipitate in urines: since the salts and sulphurs filling all the bodies, are easily fixed and clogged by acids.
Mineral Crystal, called Salt of Prunelle, page 289: crush two pounds of refined Saltpeter and put them into a crucible which you will place inside a oven on a strong fire. As soon as the Saltpeter will melt, pour over, at various times, one ounce of flowers of sulphur, and the matter will soon flame and the more volatile spirits of Saltpeter will fly off: when the most of flames will lose power, the matter will remain melted and well bright. Take hold of the crucible helping yourself with pliers and overthrew it over a plain and clean bronze basin, which will be well heated before, to make sure that all humidity has gone: turn the basin in order to spread the salt while cooling; this is called Salt de Prunelle.
It is important, to have it well pure, of making it melting in a suitable volume of water, filtering the dissolution and let it crystallize, as we have already said about the purification of Saltpeter.
It is said to be better than refined Saltpeter as a medicine, because of the presence of sulphur inside ( usage and dosage on the original page 290).