℞ What quantity you please of Nitre, dissolve it in common Wa∣ter, so much as to make it a very strong Brine or Pickle: take of this Pickle lbiv. Oil of Vitriol lbj. put them into a Cucurbit, and distil in Sand; so will you have first a Phlegm, then an acid Spirit of Nitre, which gather by it self: distil to driness, the Nitre remain∣ing in the bottom. Or thus, ℞ Nitre lbij. Oil of Vitriol recti∣fied lbj. mix them: put them in∣to a Retort, and with a gradual increase of the Pire, distil to dri∣ness; so you will have a very strong Spirit of Nitre, and in the bottom you will have a Nitre Vitriolate, which Kreuchner calls its Es∣sential Principle.
This Spirit, tho' it may be su∣spected to be adulterated with the Oil of Vitriol, yet it is suffi∣ciently grateful, and of good use in Physick; it is most subtil and penetrating, of all the acid Mineral Spirits; and therefore