Name: Robert Boyle 2008-07-18 3:47
As is before shewed, take Urine well putrefied in a Tub, exposed to the Air for seven Weeks, all one as you do when you're to make a Spirit of it; the Spirit being drawn, or rather the whole of it being evaporated to the consistance of Honey, in which lies the Fosperus; but the Art is somewhat difficult to get it from thence, in two cases, the one is in making choice of a proper Agent to be mixed therewith, and the other is the exact regiment of the Fire.
Now as to the Agent, it must not (as some have said) be Sand; but one that is free from Salt, and consequently from the glass-making Faculty, or any thing that will vitrifie, for if it doth that, you shall never obtain the Fosperus; but that you may, we direct you to make use of a Fire within and without your Vessel, which is thus to be understood; take the Sap of Urine, as before 'tis said, or that of Dung and Urine putrified together, and incorporate it with Charcoal-dust, and put it into a German Retort, and lute on a Receiver, that is filled half full with Water, that when the Fosperus comes over, it may immediately drop into the Water and be preserved thereby.
Observe, That you are to begin with a very small Fire, but you are to increase it gradually into the highest degree that possibly can be made, and let it be in such a Furnace, that upon occasion the Bellows may be used, and that the Fire may play well about the Vessel, continuing so long at its greatest heighth, till no more comes over, and you'l see Flakes like Lightening, that will come over in the Receiver of two substances, the one like a thick muddy Water, which will sink to the bottom, the other swimming over it; separate by inclination these two substances, and keep each by it self in a Glass, the gummy Nature may be made into what form you please, by being dissolved in Spirit of Sal Armoniack or other Urinous Spirits; in B. 'tis thereby putrified.