176

General Biftory o/DRUGGS.

Vol. II.

upon old Walls, Buildings, and the Urine of preferable to Common Saltpetre, and whichfeveral Animals, which has lain a long Time the_Ancients call'd Aphro-Nitrum

on Cellar Floors, or on the Stones: ThisSalt being form'd by the Acid of the Air,which after it has penetrated and rarifiedthe Stones or Earth, is thus fix'd and im-bodied.

Salpetre is feparated by Diflblution, Filtra-tion, and Coagulation ; they powder groQythe Stones and Earth that have lain a longTime in the Air, or which are taken fromold Buildings ; they fteep this in a great dealof hoc Water, in order to diffolve the Salt:They throw this Infuiion upon Afhes to makea Lixivium, or Lye ; they pafs and re-pafsthe lame Liquor feveral Times upon theAlhes ; then being clear they evaporate threeor four Quarts of the Humidity over a Fire,then they let the Liquor to cool and cryftal-lize, taking the Cryftals off to dry, and thenevaporate nlmoft all the Moifture away, andcool again as before : They take off theSa/f-pttre that contains a great deal of lixiviateSalt, and which is almoft like Sea Salt, onlythat the lixiviate Salt being Alcali, it changesirs Nature becaufe the Pores are fill'd by theAcid of the Saltpetre. The Saltpetre, madeby this tirft Purification,, is call'd CommonStltpcter ; the lalt Sort of which ought notto be mix'd with the firft, becaufe it is almoftfix'd, and consequently not fo good.

They partite Common Saltpetre by dif-folving it in Water, filtnng the Diflblution,and evaporating the Water over a Fire, 'tillthere appear a lmall Scum upon it ; thenleaving it to cool, without ftirring, therewill Ihoot fine, Jong, white, clear, transpa-rent Cryftals; pour off by Inclination, theWater that Iwims upon it, and take out theCryftals to dry, evaporating again Part of theremaining Water, and leave it to cool ; newCryftals will be form'd, which dry as before;and in (bore evaporate the reft of the Liquor,'till you find nothing at the Bottom but alittle Salt like Sea Silt: Repeat feveral Timesthe Punfjcation of your Saltpetre after thelame Manner, and every Time feparatefome of the fix'd Salt ; the more it is puri-fied, the firjer, larger, more fhining andtransparent are the Cryftals, freed from theiixed Salt, and difficult to meir. There islikewhe a Natural Saltpetre, flicking againft•Walls and Rocks in little Cryftals, which is

The ordinary Saltpetre ought to be chofewell purified, in long Cryftals, as hath beenfaid, cooling upon the Tongue, and thatcafts out a great Flame, when thrown uponhot Coals; it is aperitive, refolutive, abatesThird, provokes Urine, refifts Putrefaction,allays the Heat of the Blood, drives forththe Stone from the Kidney or Bladder : TheDcfe is from half a Scruple to a Dram.

Of melted Saltpetre, or Salt of Nitre.

Sal Kltri is a purified or refin'dSaltpetre melted by the Fire, and Pomet,put into a Skillet, and (o reducd in-to Cakes of three or four Fingers Thick-nefs.

The Salt of Nitre, made after this Man-ner, is very little in ufe, but inftead of it ismuch us'd a Preparation call d Cryftal Mine-ral, which is made by calling a little of theFlowers of Brimftone upon tome of the afore-mention'd meited Saltpetre,

Sal Nitri, or Saltpetre, is fix'd with Char-coal, and faid, when fix'd, to have the fameProperties as Salt of Tartar, and that a redTin<fture of it may be drawn with Spirit ofWine, like that of Sal Tartari.

Of Spirit of Nitre.

From any of the Sorts of Saltpetre, byMeans of a little dry'd Potters Clay, a Re-tort and Fire, is drawn a Spirit extreamlyftrong and violent, but very proper for allOccalions where 'tis requir'd.

Spirit ot Nitre, when good, is as clear asRock Water, and fends forth Fumes contin-ually, if the Bottle is unftop'd. Some rafcallyPeople fell Aqua fortis inftead of it, there-fore Care muft be taken about it, but 'tiseafily diftinguifh'd from Spirit of Nitre, bywhat I have (aid before, and by the low Pricethey fell it at; whereas true Spirit of Nitrecannot be afforded under eight Shillings thePound, or upwards.

We have but little Spirit of Nitre nowcome from Ho/land, either through the fmallOccasion we have of it, or rather throughthe Covetonfnefs of Workmen that willnot afford it, but chule to make ufe of Aqua

fortis

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