Let us now return unto the moist and cold fire of the Philosophers, and see what an admirable fire God hath hidden in Salt Peter.
That a most potent fire doth lurk in Salt Peter is not worth our confirming by any argument. That horrible Gunpowder which shakes or rends all things asunder proveth the thing most manifestly, and Aq. Fortis, which dissolveth and destroyeth all Metals, yet another fire of far more powerfull virtue is hidden in the same Salt, which very few have known and beheld, and the which we will here make manifest, for the honour of God, and the profit of all mankind.
XVIII. Of the preparation of the moist and cold fire of Salt Peter.
Take of Potters earth being without sand, and burnt, 2 parts, and 1 part of Salt Peter very well purified, with both these matters being reduced into powder and well mixed together, fill a glass retort well coated with clay, put it in a Furnace for distillation, and joyn a Receiver to the Neck of the Retort, into which put as many pints or pounds of water as there were pounds of Salt Peter mixed with the earth, that the Spirits going forth may so much the sooner be condensed into moisture, after thou hast exactly joyned and luted thy Receiver to the neck of the Retort, with a due lute (or clay) kindle a fire according to Art by degrees, and the spirit of the Salt Peter (representing a yellow or red mist in going forth) will joyn it self to the water placed in the Receiver.
All the Spirits being come forth, take off thy Receiver, and separate them from the water, put this sharp spirit of Niter into some strong glass: it being by distilation freed from its superfluous phlegm and rectified, is applied unto Medicinal and Chymical uses: concerning the operations and virtues whereof there is mention made in the second part of my Furnaces, and in the Dispensatory of Schroderus. Moreover, the manner of extracting and concentring a fire of this spirit is this.
Pour this spirit of Niter on the powder of Lap. Calaminaris or Zink reduced into small little grains that it may dissolve as much as it can: and when it will dissolve no more in the Cold, place the glass in hot sand that it may dissolve more of the matter, filtre the solution and by sand draw off all the phlegm in a glass retort; the phlegm being all come off, change thy Receiver, and increase thy fire and drive out a fiery oyl, which oyl thou shalt keep well stopt, because it uncessantly fuming would wholly vanish away in the Air.
This fiery smoke of Salt Peter, as also that of Vitriol, and common Salt, burns up all Herbs, Grass, Leaves and Flowers, and whatsoever it toucheth, just as if they were burnt with a strong heat of the Sun or Fire.
And this is the preparation of the moist and cold fire of Salt Peter, of the use and efficacious operation whereof in Medicine and Alchymy, it shall be more exactly and fully treated on in the following Chapters.
XIX. Of the moist fire of Allome.
Allome also by the work of Distillation and Concentration yields an efficacious fire most like to that of Vitriol, in efficacy and virtues, but the plenty doth not answer by reason of too much earth wherewith it abounds, yet if somewhat of the other Salts be added unto it, it rightly and orderly bestows its fire.