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from the Allies, does not cryftallize, but ffill greedily i bibcs the Acid Spirits.

Hence it may be probably concluded, that the LixivioU3, or fix'd Alcaly Salt, is no. other than the Earth of the Plant, which, notwithstanding the Violence of the Fire, has retain'd a little Portion of its acid Salt, fuflkient to diflblve it in Water ; ftill referving a fufficient Number of Zoculi or Pores, to lodge the firfl Acid that fhall offer it felf,

in lieu of that driven out of it by the Fire. And as the

Name Alcaly is only gi ven to a Salt, in refpecl of its im- bibing and retaining an Acid prcfented to it, in otder to the producing a cryftalliz'd Salt ; the Lixivious Salts of Plants may be fiid to be more or lefs Alcaline, as they abforb more or lefs of the Acid ; or, which amounts to the fame, as they contain more or fewer Vacuities to be fill'd with Acids. An Alcaly, after it has been fully fatiated with one fort of Acid, will yet Sometimes admit and retain part of ano- ther Acid : This is chiefly obferved where a Vegetable A- cid has been received firfl, and a Foflil one is offer'd after. And it terns owing to this, That the Vegetable Acid hav- ing undergone a greater degree of Fermentation in the Body of the Plant, is become rare and pervious, in refpect of the more folid and weighty Particles of the Mineral Acid; which therefore force a way in.

The fame is always the Cafe, where an Acid appears an Alcaly with refpect to another Acid ; that is, where, of two Acid Spirits, one whereof has a Mixture of fome Alcaly ; the rarer of the two having poffefs'd the Pores of the Al-

kaly, is comprefs'd by the other denfer Acid. Thus, a

Pin-cufhion, tho ever fo full of Cotton, will admit a good dumber of Pins.

Now, urinous Salts are Alkalies as well as the Lixivious Kind, i. e. they greedily imbibe Acids, retain 'em, and to- gether with 'em compofe Salts which cryflallize. — But their Volatility feems to make it plain, that they are not, like the former, a Compofition of a mere earthy Matter, with a little Acid ; in regard a mere Earth can never become Vo- latile by fuch Admixture. Yet is there a great deal of Rea- fon to imagine, that their Compofition is no other than a Part of the fame Matter, which would have produced the Lixivious Salt, intimately mix'd with a deal of the fetid Oil of the Plant ; and that the Oil is the fole Caufe of the Volatility of thefe Salts.

M. Homlerg, in his, Effai dzi Sel frincife, makes three Claffes of Acid Salts, correfponding to the three Species of Sulphurs wherewith the primitive Acids may be combined.

The firfl Oafs coniifls of fuch as contain an Animal, or a Vegetable Sulphur, which amount nearly to the fame. — To this Clafs belong all the diftill'd Acids of Plants, Fruits, Woods, t$c. which muff neceffarily retain part of the Oil of the Plant, which is their Sulphur. To this Clafs alfo be- longs Spirit of Nitre ; as being a Subftance procur'd from the Excrements of Animals, &c.

The fecond Clafs is of thole which contain a bituminous Sulphur. — Such are Vitriol, common Sulphur, and Alumn ; which are all ufually procur'd from a Mineral Stone, where- in Bitumen is the prevailing Ingredient.

The third is of fuch as contain a more fix'd Mineral Sul- phur, approaching the Nature of a metalline one. — Such are the Acids drawn from Sea Salts and Sal Gemma's ; the latter of which is chiefly found in Places near Mines of Metals, and the former probably arifes from Rocks, or Veins of Sal Gemma; running into the Sea, and there diffolved.

From the peculiar Nature and Properties of the Sulphur thus accompanying the feveral Kinds of Acid Salts, their different Phenomena and Effects are to be accounted for. — See the Article Salt.

! are doubtlefs chiefly derived from way of Food, and Nutrition ; and from thofe of Minerals. So that thcte Ihould feem to be but one Spring of Acidity : The Diverfities arife from what happens to 'em in pafling thro' the organiz'd Bodies of Plants and Animals. Hence it is, that Plants and Animals efpecially, yield a very volatile Al- kaly Salt ; whereas, the Salts of Minerals arc found altoge- ther acid, and much more fix'd and concrete ; tho 'tis the fame Matter in both Cafes, under different affumed Forms. Thus, the younger Lenicry argues, that as Animals feed on Plants, and reciprocally, in the Inftance of Salt-petre, 'iSc. Plants feed on Animals ; inafmuch as their Vegetation is excited by Manure ; it happens, that what was real Salt-petre in Plants, becomes only a nitrous Sal Ammoniac in Animals, and vice verja. — The fame Author accounts for this double Metamorphofis, by fuppofing that the nitrous Principle remains the fame in both Cafes, and in both Cafes is attach'd to the fame Matrix, with this only difference, that the Matrix becomes more earthy in Plants, and by that means, fix'd ; and in Animals, lofes its earthy Parts, and aflumes other oily ones, which render it volatile. Mem. dc I Acad. An. 1717.

As to the Marnier wherein Acids aft on Alcalies, the great Number of little Eiwhlcs produced during their Action, and

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The Acids of Am ma Plants, in the ordinary thofe of Plants, again,

the Heat anfing -thereupon M. Htmherg explains it

tlvus,-Ihe Matter of Light, which he fuppofes to' be the chyrruca) .Principle, Sulphur, and to poffefs the whole Extent of the Univerfe ; is kept in a perpetual Motion by the con- tinual Impulfes which the Sun and Fix'd Stars »ive it • But this Motion, happening on fome Occafions to be flacken'd may be retnev'd again, and augmented by the near Approach of Flame, which that Author fuppofes the only Matter capa- ble of giving Morion lo Light.— This Motion of Light can- not proceed, without continually flriking againft the foiid Bodies, and even palling thro' all the potous ones, it meets in its way. See Sulphur, and Fire.

Suppofe, now, Acids to be little, folid, pointed Bodies, fwimmmg at liberty in an aqueous Fluid, and kept in con- tinual Motion, by the repeated Impulfes of the Matter of Light ; and Alcalies, to be fpongious Bodies, whofe Pores have formerly been fill'd with the Points of Acids, and which flill retain the Dents or Impreffions thereof and are ready to receive the like Points when driven within 'em. 'Tis eafy to conceive, that if fome of thofe porous Alcalies float in the fame Liquor wherein the folid Acids float ; thefe latter, being impell'd by the Matter of Light, will enter the Cavities of the former, which are framed as it were on pur- pofe for their Reception ; and that they will do it the more readily, if the Motion of the Matter of Light, wherewith they are impell'd, have been accelerated by external Heat.

This Introduflion of Acids into the Body of Alcalies, is, in all appearance, effecfed with a great Velocity and a deal of Friction ; inafmuch as it produces fo confiderable a de- gree of Heat : And as the Pores of the Alcalies were before fill'd with an aerial Matter, which is now expell'd by the Points of the Acids ; that Air is put in Motion, and produces the Bubbles, which are fo much the more fenfible, as the Heat accompanying the Action is the greater. See Air, and Heat.

Sir /. Newton accounts for the Effects of Acids in a diffe- rent manner, viz. from the great Principle of Attraction. See Attraction.

' The Particles of Acids, he obferves, are of a fize ' groffer than thofe of Water, and therefore lefs volatile ; ' but much fmaller than thofe of Earth, and therefore much c lefs fix'd than they. — They are endu'd with a very great ' attractive Force, wherein their Activity confifts ; it being ' by this that they affea and flimulate the Organ of Tafle; ' and by this alfo, that they get about the Particles of Bo- ' dies, cither of a metalline or ftony Nature, and adhere ' clofely to 'em on all fides ; fo as fcarce to be feparable from them by Diftillation or Sublimation : and when thus ' gather'd about the Particles of Bodies, by the fame Power ' they raife, disjoin, and fhake them one from another - ' that is, diflblve 'em.' See Dissolution.

' By their attractive Force, alfo, wherewith they rufh to- ' wards the Particles of Bodies, they move fluid ones, and ' them into Air, and generate Bubbles : and hence all vio- ' lent Fomentation ; there being in all Fermentation a la- ' tent Acid, which coagulates in Precipitation.' See Fer- mentation.
 * excite Heat; ihaking afunder fome Particles, fo as to' turn

' Acids, alfo, by attrafling Water as much as they do the ' Particles of other Bodies, occafion the diffolv'd Particles ' readily to mingle with Water, or fwim or float in it • after ' the manner of Salts : And as this Globe of Earth, 'by the ' Force of Gravity, attracting Water more ftrongly' than it ' does lighter Bodies, caufes thofe Bodies to afce'nd in Wa- ' ter, and go upwards from the Earth ; fo, the Particles of ' Salts, by attracting the Water, mutually avoid and recede ' from one another as far as they can ; and are thus diffus'd ' throughout the whole Water.

' The Particles of Alcalies confifl of earthy and acid <■ Parts united together ; but thefe Acids have fo great an 1 attraftive Force, that they can't be feparated therefrom bv ' Fire ; and that they even precipitate the Particles of dif- ' folv'd Metals, by attracting from them the acid Particles ' which before had diffolv'd, and kept them in Solution.' See Precipitation.

1 It thefe acid Particles be join'd with earthy ones, in a ' fmall Qu an »'y j 'bey are fo clofely retain'd by the latter as ' to be quite fupprefs'd and loft, as it were, in them • fo that ' they neither flimulate the Organ of Senfe, nor attract Wa- ' ter; but compofe Bodies which are not acid, i. e. fatty and ' fweet Bodies ; as Mercurius Dulcis, Brimftone, Luna Cor- ' nea, \Sc. — From the fame attractive Force in thefe acid. c Particles thus fupprefs'd, arifes that Property of fat Bodies ' that they flick or adhere to almott all Bodies, and are ea- ' fily inflammable. — Thus, the Acid that lies fupprefs'd in 4 fulphureous Bodies,by more ftrongly attract ing the Particles ' of other Bodies (earthy ones for inftance) than its own - ' ptomotes a gentle Fermentation, produces and cheriifies ' natural Heat, and carries it on fo far fomctimes, as to the ' Putrefaction of the Compound; Purrcfacf ion arifina hence c that the acid Particles which have long kept up the Fer- ' mentation, at length infinuate into the little Interftices that

' lie