XXV. Another gainfull way of making good and burning Salt Peter out of common Salt, by the help of fixt Salt Peter.
Commix equal parts of the Scoria’s of fixt Salt Peter that you have used, and of the common Kitchin Salt together, and add thereunto twice as much Calx-vive first reduced into Powder by lying in the Air, [as they both weigh.] Of this mixture make up round Balls, and so pile or stow them with Wood, that it may be a Stratum Superstratum, [or a Bed of each orderly,] as the Chymists call it. Kindle your pile of Wood and let all your Balls be red hot for an hour: And the fixt Salt Peter will by a wonderfull inversion transmute the nature of the common Salt, and turn it into Salt Peter, but yet not inflamable till the Salts have been moistned some due time, and so attracted a life out of the Air, and made fit to conceive a flame, or to burn.
N. B. If instead of Rain water you use such Waters as you have already used and extracted your Minerals withall, to moisten your mass with, then will you thence get in some few Weeks space, an inflamable Salt Peter.
But forasmuch as in the extraction of Minerals and separation of Metals, there will be such a great quantity of sharp nitrous Waters, and likewise of fixt Salt Peter offer themselves for the accomplishment of this operation, and so great a benefit and gain is gotten by that so plentifull an augmentation of your Salt Peter (which hath already Sufficiently profitably paid your costs) out of vile and common Salt; hence clearly follows, that all those hitherto described labours and operations are effected, in a manner without any costs or expences, which is indeed an unheard of thing, but yet most true, and exceeds the belief of ignorant Men.
XXVI. The reduction of Silver extracted out of the Minerals, and freed from the Aq. Fortis by abstraction, [or drawing off the said Aq. Fortis.]
The Silver from which Aq. Fortis has been drawn by Distillation, needs not any matter to help on fusibility, for as much as it doth of its own nature admit of a very easie Flux; but that the Fugitive Spirits that adhere unto it would carry away somewhat of the same. So now, to prevent this discommodity, you may add unto such a Silver a little of the fixt Salt separated out of the Lixivium [of fixt Peter,] the which Salt Alkaly will mortifie the acid spirits so, that they shall not be able to carry off any thing at all in the melting.
XXVII. The reduction of extracted Copper.
If the Copper be not mixt with any other Metals, and be but little in quantity, it may be reduced so in Crucibles by it self, but if it be in a plentifull quantity it may be done by blast.
But where it contains Iron or Lapis Calaminaris, (which two the Minerals [of Copper] do frequently abound withall) there it admits not of reduction per se without the help of other matters, because of the Iron, Zink, or Calaminaris; which Minerals associating themselves with the Copper, in the melting are wont to make it brittle. But this inconveniency may be prevented the following way.