dard. Thus, for example, if the goodness of fublimate be fufpected, take STATICS. an ounce of fome that is known to be fine, carefully balance it in oil of turpentine, and note its weight therein; then, an ounce of the fufpected fublimate being weigh'd as the former, if it prove of the fame gravity with the ftandard, it may be fuppofed good; but if it weighs lefs, 'tis a fign it wants a due proportion of mercury. The fame method is applicable to Mercurius dulcis, and many other bodies, wholly, or partially diffoluble in water; as alum, which is often fophifticated with fome bafer falt; to Roman vitriol, which is, fometimes, either counterfeited, or adulterated, by roch-alum and a tincture of copper: and, according as the weight of the body in oil recedes more or lefs from that of the ftandard; fo the adulteration may be probably concluded lefs, or greater.

I might, alfo, obferve another ufeful way of eftimating the gravity of Another way of folids and fluids, by taking a heavy folid, and carefully obferving, once if gravity of finding the Spe for all, its weight in the air; then weighing the fame, firft in one of the fluids. liquors to be examin'd, and afterwards in others: whence, the difference between the folid, and each of the fluids being obferv'd, 'tis easy to find the specific gravity of each, and to affign the proportions betwixt them.

But if only one folid be employ'd, 'tis neceffary fuch an one be chofen ; as hath a much greater fpecific gravity than is barely neceffary to fink it in water; because fome liquors are much heavier than that: nay, it ought to be heavy enough to fink in all fluids, except quick-filver, if 'tis defign'd for experiments in general. But 'tis not very easy to pitch upon fuch a fingle folid as hath all the qualities requifite to our purposes: for, it ought not to lofe any of its weight by the infenfible avolation of effluvia, yet be of a confiderable fpecific gravity, and not too large, or intenfely heavy, left it overload a tender balance, or require too much liquor to furround it; its texture fhould be proof against sharp and piercing menftrua; it fhould, alfo, be of a make not liable to be broken or fpoil'd; and, laftly, of a natural, uniform, and procurable fubftance.

Brimftone, hard wax, ivory, and white marble, have been, when properly shaped, feverally made ufe of for this purpose; yet they all wanted one or other of the defirable qualifications mention'd. I, therefore, frequently employ'd three other bodies, as more proper. The first was a piece of amber, between three and four drams in weight, of a high yellow colour, very transparent, and of an uniform texture, and convenient figure. This we apply'd to examine the lighter fort of liquors, fuch as water, wine, brandy, &c. but 'tis not proper for the more ponderous liquors, fince 'twill float at the top thereof.

The fecond is a globular glafs, which I caus'd to be blown at a lamp, and to be hermetically feal'd at the neck, that was purpofely made very fhort, after there had been lodg'd therein just as much quick-filver as we guefs'd would ferve to fink it in any fluid, except mercury. This, by reafon of its great bulk, in proportion to its weight, was fit to difcover minute differences in the gravity of the liquors 'twas weigh'd in, and

could

STATICS. Could not be corroded by fharp menftrua; and, therefore, on feveral occafions, I prefer'd this inftrument to either of the other.

thereof.

But this being too liable to accidents, for experiments that are to be imparted, and recorded for pofterity; I made ufe of rock-crystal, which, on account of its numerous good qualities, affords a fit meafure, whereto other bodies may be compared. Of this pure concrete, we employ'd an almost compleat globe, weighing in the air two ounces, thirty-three grains; wherein were two fmall holes near one another, that might eafily be ftopped up with hard wax, after an horfe-hair had been run thro' them; by means whereof it was eafily faften'd to the fcale, and made to hang in the water. The bulk of this fphere made it the more fit to discover small differences between liquors, in point of gravity. But, becaufe we may have often occafion to know the weight of fluids, which, by reafon of their fcarcity, we can command only in fmall quantities; as chymical oils, tinctures, effences, &c. we provide for fuch liquors an hexagonal prifm of natural cryftal, with a kind of pyramid at one end; which, by reafon of its oblong figure, might be commodioufly weigh'd in a flender cylindrical glafs, that required but a fmall quantity of liquor to furround a body fo conveniently fhaped, and that weigh'd in the air but half an ounce, and fixteen grains. And, to render the obfervations made with these two bodies upon medicinal, and other liquors, the more useful; let it be taken notice of, once for all, that the ball of cryftal was to an equal bulk of water, as 2.57 to 1, or thereabouts; and the prifmatical oblong piece, as 2.66 to 1, to

the fame.

I have been the more particular upon the way of trying the gravity of feveral liquors with one folid, because a double application may be made of it on feveral occafions, ferviceable to chymifts, phyficians, apothecaries, and others.

The feveral ufes And, firft, a piece of clear amber, or fome fuch convenient body, that is not too little, nor, in fpecie, too heavy, may ferve the chymift, apothecary, &c. to make probable gueffes at the degree of fpirituofity, or tenuity, to be found in many liquors belonging to the vegetable, or animal kingdom; and this with far lefs error, than by thofe figns whereon the common conjectures are grounded. For, a ftandard-liquor being provided, 'twill be eafy, by obferving the different weights of amber in feveral fluids, to judge of the fineness of any of them in its kind; for, cæteris paribus, that is the thinneft, or abounds moft in fpirituous parts, where the folid weighs more than in another; as, for inftance, the amber we employ'd, that in water weigh'd 6 grains, weigh'd in common red French wine 8 grains; in common brandy, of a pretty good fort, 17 grains; and in fpirit of wine, highly rectify'd, 34grains. The fame way may be employ'd to judge of the ftrength of fpirit of vinegar, &c. But here it muit pafs for a general rule, that, probably, as in liquors the folid weighs more or lefs, according as the liquor 'tis weigh'd in, is more or lefs fpirituous; fo, on the contrary, in acid fpirits and liquors, the less the folid weighs, the ftronger the fluid muft be reputed; that greater decrease

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of weight proceeding ufually from the greater proportion it contains of STATICS. fixed falts.

'Tis another advantage of this method, that as the common way of trying the goodness of fpirit of wine, brandy, &c. by fetting fire to a fpoonful of them, to fee how much is inflammable, and what portion of phlegm will be left behind; whereby, in tract of time, a confiderable lofs is fuftain'd; the proper proof may be made in our way, without any fuch

expence.

By thefe obfervations, alfo, eftimates may be made of undiftill'd liquors of the fame kind; as, feveral forts of beer, ale, cyder, &c. and the fame folid may be employ'd to compare liquors of different kinds with each

other.

But if the liquors to be examin'd are very ponderous; amber will not be a proper folid in this cafe: for I have found, by trial, not only that it fwims or floats in feveral fluids made by folution of falts, whether in the moift air, or with water; fuch as oil of tartar per deliquium, a folution of the falt of pot-afhes, &c. but that fome diftill'd liquors would not fuffer it to fink to the bottom of them; as I found in oil of vitriol, fpirit of nitre, and even good fpirit of falt.

There is ftill another ufe to be made of our hydroftatical folid, which may frequently be as confiderable, in general, by affifting in proportioning the ftrength of menftrua; as the former is to difcover the ftrength of particular liquors already prepared. For there are many experiments that do not fucceed fo well, unlefs the liquor be of a determinate degree of ftrength. Thus, I have found, that if Aqua fortis, whofe ftrength is reckoned the best quality it can have, were rectify'd too high, it would not diffolve filver; but require to be weakned, by an addition of water; and that it would not near fo well diffolve the rafpings of crude lead, when only moderately ftrong, and fit to diffolve filver, as when confiderably diluted with water. And in making extracts from many vegetable fubftances, chymifts them felves may fall into a mistake, by affecting to employ their most rectify'd fpirit of wine, as the beft menftruum for their purpofe; for the medicinal virtue of many fuch bodies does not wholly refide in what they call their fulphur, or rotin, which indeed is best diffolved by highly rectify'd fpirit of wine; but in a more gummy, and, perhaps, mucilaginous fubftance, for whofe extraction a moderately low fpirit is more proper. Thus we fee that gum-arabic, gum-tragacanth, &c. are indifpofed to diffolve with the beft rectify'd fpirit of wine, but readily mix with more aqueous liquors. And fome bodies, tho' diffoluble in both kinds of menftrua; yet open lefs eafily to ftrong fpirit of wine, than waterish fluids, as may be obferv'd, particularly, in myrrh.

And thus much may ferve to fhew how ufeful it will be, on feveral occafions, to regard the degree of ftrength of the menftruum, or liquor, employ'd in any curious experiment; fo that when it fhould be repeated to the fame purpofe only, we may be able to bring the fluid we make ufe of, to the fame degree of ftrength with that before employ'd, which produced

the

STATICS. the defigned effect. But, in very accurate experiments, 'tis proper to obferve, W that if the liquor be very ponderous in fpecie, as oil of vitriol, or oil of tartar per deliquium; fomething ought to be placed in the fcale, from which the folid hangs, to compenfate for the increas'd part of the hair, which muft be confider'd as a fomewhat lighter body than the fluid, and, therefore, capable of buoying up the folid.

Still other methods for the fame purpose.

Befides the method juft mention'd, there is another, which we have often found of fervice, in comparing the weight of different liquors of the fame magnitude. This is done by fucceffively filling a vial, furnish'd with a long, flender cylindrical ftem, to a certain ftanding mark, made near the top, with the feveral liquors, to be, by weight, compared together. But this not being hydroftatical, I fhall no longer infift upon it here. To proceed, therefore, there is, likewife, another way to difcover whether two or more liquors propofed, differ in fpecific gravity; and to make fome eftimate of their difference: viz. by a hollow cylinder of brafs, or other metal, made fomewhat heavy at the bottom, that it may fwim upright; which will fink more or lefs, in feveral liquors, as they are lighter or heavier than one another. But Merfennus, who propofes this way, confeffes it to be very difficult to make fure obfervations thereby; to which I add, that the metal may be corroded, or otherwife affected by urinous menftrua.

What Mersennus faid of this inftrument, is applicable to a different one, made of two glafs bubbles, and a very flender ftem, which is hermetically fealed; with a ballaft of quick-filver, in the loweft, to keep it fteady, when partially immers'd in liquors; where like the metalline cylinder, it finks deeper in the lighter than in the heavier, according to their differences in gravity. But tho' I have often employ'd this inftrument, and found it ferviceable, when I made use of several of different fizes, according to the various liquors I was to examine; yet it is, in many cafes, inferior to the

balance.

Merfennus, alfo, propofes another hydroftatical manner of weighing liquors in water, thus. Take a glafs vial, to which, being first weigh'd in air, and then in water, you are exactly to fit a ftopple of wax, or cork; this done, fill the vial with the liquor you would examine, fo that no air be left between that and the topple: the veffel, thus fill'd, is to be weigh'd in water; and fubftracting from its weight there, that of the glafs in water, and alfo that of the ftopple, the remainder will give the weight of the liquor in water. This may, perhaps, be ferviceable, on fome occafions, yet, I fear, it is troublefome, in practice; for, ordinary vials, capable of containing a competent quantity of liquor, are ufually too heavy to be applied to tender balances; and common ftopples will be fubject to various inconveniencies: for which reafon, I prefer to it a method I formerly thought of, and which I have, fometimes, put in practice, by chufing a fmall round vial; and, inftead of ordinary itopples, fitting it with one of glafs, carefully ground to the neck of it: for, by this means, the inconveniencies of ftopple, lighter than water, were avoided; nor would that alter its specific gravity, either by abforbing, or evaporating; nor would it be penetrated

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by the most fubtle, or corroded by the moft fretting fpirits: to which may STATICS. be added, (because, in fome cafes, it is confiderable) that a glass stopple will not communicate any tincture, or extraneous quality to the liquor; which cannot be faid of cork, or wax, in regard of fome fubtile, and very corrofive liquors. This vial, then, together with its ftopple, being carefully weigh'd, firft in air, and then in water, to fettle the gravity of the whole inftrument; we fill'd it exactly with the liquor to be examin'd, and proceeded as if we were to weigh quick-filver, in the manner already defcribed the weight of the given liquor in water being thus obtain'd, its proportion, to an equal bulk thereof, may be eafily difcover'd. This way of examining liquors has its ufe; and I the rather, fometimes, made choice thereof, becaufe 'tis applicable to all kinds of fluids, whether heavier in. Specie than water, or lighter.

Laying afide the ftopple, the round ball may serve, on feveral occafions, inftead of the hydroftatical bucket, formerly mentioned; for the weighing of quick-filver, and heavy powders; efpecially coarfe ones. But, if the inftrument be fitly shaped, and not too heavy, a greater conveniency than this attends it: for when you have liquor enough to furround the bottle, it may be commodiously fubftituted for the hydroftatical bubble, with quickfilver; its exact ftopple fupplying the place of an hermetical feal: and, befides, 'tis far lefs fubject to break than a bubble. That I made most ufe of, which weigh'd about 709 grains, being well ftopp'd, with only air in it, would fink, by its own weight, in brandy, wine, water, &c. And, if it were to be employ'd in liquors much more ponderous than water, as Aqua fortis, oil of tartar per deliquium, &c. 'twas eafy to fit it for them, alfo, by putting into it a quantity of quick-filver, of a determinate weight, before it be ftopp'd; which balaft, when the operation is over, may be eafily taken out, and kept a-part for the like uses.

But, notwithstanding all this, fince glaffes of a proper fize, shape, and weight, fit for tender balances, and furnifh'd with exact glafs ftopples, are very difficult to procure; and fince the way itself is fubject to fome inconveniencies, it feems, in general, that this way of finding the weight of liquors in water, is inferior to the more fimple ones, before recommended.

Having now laid down the method of weighing one liquor in another, The use and ad 'tis fit we fubjoin fome application of it.

vantages of weighing one

Among other advantages of hydroftatics, to a fagacious phyfician, 'tis fluid in another. none of the leaft, that it gives him the fpecific gravities of various liquors; which may not only help to diftinguifh the genuine and good, from the adulterate and decay'd, but ferve to other purposes alfo. Inftances hereof are afforded by the juices of herbs, and fruits; a determinate quantity of which, being firft weigh'd in the hydroftatical bucket; and fome oil of turpentine poured on it, we fink it warily in the fame liquor, whofe fpecific gravity to refined filver, or clear rock cryftal, is before-hand carefully regiftred for thus fubftituting this oil for common water, we may difcover the fpecific gravity of liquors that would mix with water. And, VOL. II.

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