The history of the Royal-Society of London for the improving of natural knowledge by Tho. Sprat.
Sprat, Thomas, 1635-1713., Cowley, Abraham, 1618-1667. To the Royal Society.

To Refine SALT-PETER.

AFter you have made your Copper very clean, put in as much Water as you think will dis∣solve that quantity of Peter you purpose to Refine, when the Water is very hot cast in the Peter by lit∣tle and little, stirring it about with a Ladle, that it may the sooner dissolve, then increase the Fire till your Liquor begin to boyle: In the mean time feel with the Scummer, whether there be at the bottom any Salt undissolv'd and take it out, for it is Com∣mon-Salt, and doth not so soon dissolve as the Peter; then as the Water boyls scim of the Froth that swims at the top of it as fast as it riseth; when it hath boyled to the height that a drop of it will coagu∣late on a Plate, (as hath been said above in the ma∣king of Salt-Peter,) then cast in by degrees either a Pint of the strongest Wine-Vinegar, or else four Ounces of Allom beaten to powder (some choose burnt Allom,) and you shall observe a black Scum to rise on the top of the Liquor, which when you have allowed some time to thicken, you may easily take off with the Scummer; repeat this so often till no more Scum arises. Some do use to throw in a Shovel full of quick-Lime, and say it makes PeterPage  274 the whiter, and Rock the better; you must take great care all this while the Fire be not too strong, for while this is doing, the Liquor will be apt to boyl over, and will not easily be appeased without your great loss.

When this is done, lade out the Liquor into a setling Tub, and cover it over with a Cloth, that it cool not too soon, and within an hour or two a thick yellow Faeces will fall to the bottom of the Tub, then quickly draw of the Liquor while it is hot, into the shooting Trays or Pans, and do as you did in making Peter, saving that you must cover the Trays with a Cloth, for then the Liquor will begin to shoot at the bottom, which will make the Peter-Rock into much fairer Chrystals, than otherwise it would: When no more Peter will shoot (which is commonly after two days,) pour off the Liquor that swims at the top, and put the Peter into a Tub with a hole at the bottom for to drain, and when it is dry, it is fit for use.

The Figure of the Chrystals is Sexangular, and if it hath rightly shot, is fistulous and hollow like a Pipe.

Before I proceed to tell you, how this darling of Nature (the very Basis and Generation of Nu∣triment) is converted into Gun-powder (the most fatal Instrument of Death that ever Mankind was trusted withal) I will crave leave to acquaint you with a few Speculations I have of this Salt, which if I could cleerly make out, would lead us into the knowledge of many noble Secrets in Nature; as also to a great improvement in the Art of ma∣king Salt-Peter.

First then you are to observe, that though PeterPage  275 go alway in Gun-powder, yet if you fulminate it in a Crucible, and burn of the volatile part with Powder of Coal, Brimstone, Antimony or Meal, there will remain a Salt, and yet so fixed (very unlike Common-Salt) that it will endure the force of almost the strongest Fire you can give it; which being dissolved into Water and Spirit of Nitre drop∣ped into it, till it give over hissing (which is the same with the Volatile part that was seperated from it in the fulmination) it will be again reduced to Chrystals of Peter, as it was at first, which noble Experiment the World hath already been taught by an honourable Member of this Society; with a train of such important Observations, as never be∣fore were raised from one Experiment.

That which I aim at then is, that if the Spirit of the Volatile Salt of Soot, or of the Urine, Blood, Horns, Hoofs, Hair, Excrements, or indeed any part of Animals, (for all abound with such a Volatile Salt fixed, and Oyle as Peter doth) could by the same way or any like it, be reduced to Peter or some Nitrous Salt not much differing from it: It would excellently make out a Theory that I am much delighted with, till I am convinced in it; which is, that the Salt which is found in Vegetables and Animals, is but the Nitre which is so univer∣sally diffused through all the Elements, (and must therefore make a chief Ingredient in their Nutri∣triment, and by consequence of their Generation) a little altered from its first Complexion: And that the reason why Animals that feed on Vegetables are obliged by Nature, to longer meals than those that feed on other Animals; is, because Animals are fuller of that Salt than Vegetables: And in∣deed Page  276 such Animals are but Caterers of it for Man; and others whom Natures bounty gratifies with a more lusty and delicious Dyet.

I confess I have been the more confirmed in this fancy, since I have often seen a Friend of mine, with a Natural and Facile 〈 in non-Latin alphabet 〉, convert the greater part of Peter, into a Salt so like the Vola∣tile Salt of Urine, that they are Scarce to be distin∣guished by smell or tast, and yet he adds nothing to it that can possibly be suspected to participate of that Nature: But indeed all Volatile Salts are so alike, that it is not easy to distinguish them in any respect.