Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/410

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ers. This makes a folution of mercury in fp'trit of nitre muddy after fome time, and finally precipitates from it a fmall quantity of a white powder. After this all the fait or flowers afcend j thefe flowers, diflblved in warm water, re- cryftallize themfelves in it when cold, afluming the fame form with that they had in the flowers, except that the com- binations of particles are more dehfe and heavy. The ufual method of making this/a/* has been this. Take a glafs retort, with a large neck, put into it four ounces of borax in fine powder, and~pour on this half an ounce of com- mon water to wet it into a fort of foft pafte j then add to this an ounce and two drachms of concentrated oil of vitriol ; place the retort in a reverberator)' furnace, and give at firft a fmall fire, which raife by degrees till the retort is red hot: there will pafs over into the receiver about an ounce of aqueous matter; and after this the flowers, or fedative fait-, will rife with a little more humidity ; hence fome part of the flowers will be diflblved in the liquor, and run over into the reci- pient, but the greater quantity will remain in form of a dry fublimation in the neck of the retort ; they will finally ftop up the whole orifice of the neck, and what arifes after this ufually forms a circle of a fort of glofly fait, about their bafes, out of which the flowers feem to {hoot. They are compofed of multitudes of fine thin blades, or flakes, and are eafily brufhed out of the neck of the retort with a feather ; the glofly circle at the bottom of them may be diflblved in water, and recryftallized, and by this means all the fait will be procured.

Mr. Geoffroy the younger has given, in the memoirs of the Paris academy in 1732, an account of a way of making this fait by folution and cryftallization alone, without the trou- ble of diftilling ; he has alfo fummed up the feveral other ways of making it with blue and white vitriol, but the me- thod here mentioned is that by which the chemifts now make it. Mem. Acad. Par. 1732.

Shivery Salt. See the article Shivery.

Vitreous Salt, in chemiftry, a term ufed by fome modern chemifts for a kind of fait, which till of late has wanted a name, and which is found in and feparable from the fixed alkaline fa Its of vegetables.

It is bitter, hard, fixed, and not alkaline, and of a cryftalline or glofly appearance.

The method preferibed by Boerhaave for the procuring it with mod eafe, is this : put fix pounds of the beft pot- afhes into a clean glafs, add thereto twenty pints of cold rain water ; ftir them together with a flick, and fuffcr the whole to reft. When the afhes are thoroughly diflblved, gently decant the clear lixivium ; and there will be found at the bottom, mixed with the faces, a number of fmall greyifh granules, of a bitter tafte, and of an almoft glafly brittle- nefs and hardnefs ; thefe are the fait required, and con- tain no alkaline quality ; but to obtain it in greater purity, diflblve fix pounds of pot-afhes in fourteen times their weight of water ; filter the lixivium while hot, and make it per- fectly clear ; then put it into a glafs veflel ready heated, and moiftened, and fufier it to ftand ; a dufky cruft will foun begin to fhoot to the bottom and fides of the glafs. and will gradually become thicker and thicker ; at length when no more appears to fhoot, pour off" the liquor, and there will remain behind a fait like the former, but purer, and in larger quantity : if the remaining lixivium be boiled a little, and fet to cryftallize again, it will afford a fmall quantity more of this fait ; but after this it will yield no more ; whence there feems to be only a certain and deter- minate quantity of this fait contained in the alkali. If this fait be put into a veflel of rain water and fhook about, it does not diflblve, only the alkali wafhes oft", and the fait remains purer than before ; after this it is to be gently dried and kept. Boerb, Chem. P. 2. p. 42.

It is well known among the chemifts, that genuine fixed al- kaline fa Its can hardly he cryftailized ; and though fome have produced this fait as a cryftailized alkali, the fallacy of the pretext is evident, fince this appears on trial to be no alkali at all ; and it remains not lefs difficult than before to cryftallize pure alkali, though a fait different in its nature from it, may be cryftailized in a certain quantity from among it.

This vitreous fait never runs fpontaneoufly in the air, nor does it eafily diflblve hi cold water ; when boiled it re- quires a large proportion of water to diflblve it, and as foon as cqld it eafily feparates itfelf from it again : it is laftingly bitter to the tafte, and crackles very much when thrown into the fire : it is neither acid nor alkaline, nor approaches in its nature to any other fait hitherto known ; but feems neareft of all others to refemble fandiver. This may fuggeft a query,

■whether the fire in producing the fixed alkali, does not at

-the fame - time produce this fait from vegetables ; and whe- ther by combining the fand and alkali together in glafs-mak- ing, the fire does not again feparate and throw up this fait in fandiver. Something of this kind feems to be the cafe, and a clofe inquiry on thefe principles may fhew us why tartar, in the rate of an alkali, does not afford this fait} for tartar proceeds from a fubtile liquor, intimately fer- mented in all its parts. There yet remains the trying this

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fait on various bodies, by means of fire, to give a true knowledge of its nature, which is at grefent tco little known. This is to be obferved, however, that it differs fo much from the alkali, in which it is contained, that the careful chemift, before he makes ufe of that alkali in any nice procefs, or experiment, ought carefully to fepaiate this neutral _/#// from it. Boerhaave' sChcm. P. 2. p. ico. FuftbieSALT of urine. This fait, otherwife called by fome fa I mierocpfmi, and native fait of urine, is extracted from urine in a particular manner.

It is beft prepared from putrified human urine; but it may be prepared from frefh. A quantity of the urine of found beer drinking men being putrified in a moderate heat, and then fiowly boiled in glazed earthen veflels to the confidence of a fyrup ; if this liquor be placed in a cellar or cool place, in about four weeks time, or fooner in winter, cryftals of a peculiar figure will be formed. But thefe being impure, muft again be diflblved in a fuflicient quantity of water, and filtered as hot as poflible through grey paper, and the folution again put in a cool place, where in a few days cryftals will again be formed much cleaner than the former. Thefe being feparated from the liquor and dried, the opera- tions of folution, filtration, and cryftallization, muft be reiterated twice or thrice, till the fait becomes perfectly white and without fmell.

Mr. Marggraff fays, that 100, or 120 meafures of urine give about three or four ounces of this fait, which always cryftallizes firft, and is eafily diftinguifhed from that which appears afterwards in cryftals of a long and cubical form. This fait is ammoniacal, but of a peculiar nature. It is a faline acid body. By diftillation an urinous volatile fpirit firft rifes. The refiduum may be reduced by a violent fire into a pellucid white tranfparent mafs like glafs, of a very fixed nature, and from which neither acid nor any thing elfe can be feparated, without the addition of fome other matter.

This vitreous fubftance may be entirely diflblved in two or three parts of diftilled water, and is thereby changed into a tranfparent liquor, fomewhat thick, not unlike the concen- trated oil of vitriol, and having the properties of all acids, fuch as fermenting with volatile and fixed alcahes, forming neutral fa its with them, precipitating bodies diflblved in al- caline menftruums, and ditfblving alcaline earths. It does not diflblve gold nor filver ; and copper, tin, and lead lit- tle j but iron very ftrongly. It extracts a red colour from cobalium fro cteruleo, in German, blau farben-hobalde, the mineral by which glafs is tinged blue.

But this fait, in its dry ftate attracts metals with much more vigour, and with them produces feveral remarka- ble and lingular phenomena ; for all which, as alfo for the relation their fait bears to acid, alcaline and neutral falts, we refer to the learned author, who has alfo examined its effects on feveral folutions of terreftrial bodies. One moil eminent property is, that mixed with the inflammable part of foot, and diflblved in a clofe veflel, it produces a phofphorus. An ounce of this fait of urine thus feparated from its urinous part, and exactly mixed with half an ounce of foot, affords in this way a drachm of the belt phofphorus. The refiduum did not produce any when tried. The learned author does not pretend to determine exactly the true origin of thxs fait, he thinks its acid may come in- to the human body from vegetable aliments. He has ob- ferved elfewhere that crefles, milliard, rocket, and even corn expofed to a very violent fire, produce a phofphorus. Hence he thinks this acid muft be mixed with thofe fub- ftances ; and the like may happen in other vegetables. He thinks this conjecture ftrcngthened, becaufe urine in finn- mer, when people eat molt vegetables, always produces this fait in the greateft quantity. Marggraff, in Mem. de l'Acad. de Berlin 1746. See alfo Mifeel. Berol. Tom. VII.

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Sprit of Salt. This menftruum diflblves iron into a yel- lowifn green liquor, and copper into one of a very deep yellow colour : tin diflblves in it with great violence and noife, and in great quantity ; the folution becomes a thick but pellucid fluid: lead alfo diflblves in it ; but after this folution has ftood for fome time, there always fubfides to the bottom a white powder. Silver, if it is perfectly pure, does not diflblve in fpirit of fait, but if it contain ever fo little copper, as it is very feldom met with perfectly pure from that metal, its furface is then always corroded, and its colour fullied. Spirit of fait diflblves mercury into a limpid liquor ; if diluted with water it does not diflblve the regulus of antimony ; and if this regulus is diflblved by the moft concentrated fpirit of fait, if a little water be added, or it be only expofed to a moift air, it is reduced to a fine powder. Zink diflblves eafily and perfectly in this men- ftruum. Cra?ner'$ Art of Allaying, p. 38.

S alt -marjb, faiina, a place where fait is made, of which there are many natural ones in the hotter countries, where the fea exhaling the water of fait lakes, leaves the fait dry and ready for ufe at the bottom, without any art or labour of man to make it : thus in Mufcovy and fome other places there are whole fields of fait. See bay Salt, fupr.

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