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of the different plants; but befidcs this It mull he allowed, that there arc feveral accidents by which the fait may alfo be rendered of a different nature, or at leaft its natural di- verftty from others may be encreafed, and fet in a ftronger light. The different manner of burning the plant will oc- cafion a great change in the fait it yields ; and two different fain will be obtained, if one half of the fame quantity of afhes be lixiviated with hot water, and the other half with cold. This has been fully proved by Stahl in his Funda- fnenta Cbemica.

Thefe are only accidental differences in the fame fait ; what Mr. Gmelin takes upon him to prove by experiment, is, that there are more real differences between the fa Its of va- rious plants, and thofe wholly dependent on the nature of thofe plants, than had been before fufpecled. That the fits of plants may be fairly compared together, it is neceflary that they mould all be made in the fame man- ner ; the fire mould, in all the procefTes, be raifed to the fame degree, and the time of the plants remaining in it fhould be alfo afcertained, and the lixivium from cachbe pre-

. pared in the fame uniform manner : thus the volatile parts of one plant will be no farther evaporated than of another, and the lixivia will contain an equal fhare of the principles of the feveral plants, proportioned to their feveral natures ; for it is a certain faci, that if the lixivium of the fame afhes

■ be made in part with hot water, and in part with cold, the fait, obtained from that made with the hot water, will con- tain more of the earthy and oily parts of the plant, than that made with the cold.

The method of making a fixt lixhial fait of a plant, fo as to retain as much as may be of the virtues of the plant, is this. Let the plant continue on fire without breaking out into flame, and let the fire be continued till it fall into afhes, but no longer, left fome of the volatile parts be driven off, which might have been preferved. Cold water, and not hot, fhould be ufed to make the lixivium, that the fait may appear in its proper form; and as the water of wells, rivers, and other places, differ greatly from one another, the water ufed for this purpofe mould be fuch, as has been previoufly diftilled two or three times over, and fo rendered perfectly pure, and kept in glafs veffels, not in earthen, leaden, or wooden ones, left it contrad fome adventitious particles. Now if the lixiviums of plants, made with all thefe cautions, are found to differ from one another, there is no room to doubt, but that the falts of thofe plants are really different one from another.

This evidently appeared from the labours of a Swedifh che- mift, whofe papers fell into Mr. Gmelin's hands, and who had with all this care and caution prepared the falts of a number of plants ; a copious table of the different effeefs of which, in different mixtures, is added to Mr. Gmelin's ac- count : but not only the falts, but the very afhes of diffe- rent plants, prepared in the fame exact manner, are found to differ obvioufly to the fenfes. The afhes of mugwort, fmall centaury, chervil], and dill, are of a brown ifh grey; goats beard and lingwort afford white afhes ; thofe of fanicle

' are whitifti ; thofe of Roman wormwood of a grcenifh grey ;

■ thofe of rue, agrimony, and faxifrage, brown ; thofe of tanfy of a dufky green ; thofe of dodder of a fine green ; eyebrigbt, fouthernwood, common wormwood, and fcabi- ous, afford them grey ; fcurvygrafs of a whitifh grey ; hyf- fop, yarrow, and fowbane, of a dufky grey; melilot and oak leaves, as alfo plantain, colts foot, pine tops, and fu-

- mitory, of a dufky brown ; pennyroyal of a pale brown, with fome fpots of white ; elder flowers, fage, and mother of thyme, afford yellow afhes ; thofe of ftrawberry leaves are of a pale brimftone colour ; thofe of catmint of a dufky red ; of prunella brick coloured ; of honeyfuckle blue ; of fern

'■■ blackifh ; and thofe of St. John's wort, feverfew, origanum, and pimpernel, are all of a deep black. The quantity of allies, produced from an equal weight of dif- ferent plants, is very different, fome yielding a feventh part of their weight, others but a twelfth or thirteenth, and fome particular plants much lefs than this; St. John's wort in particular yields but a twenty eighth part, and fern but a twenty fourth.

The lixiviums made from thefe different afhes were fome colourless from the beginning, others at firft were bluiili. greenifh, or of other colours, but thefe tinges all went off after a few days, and the liquor became limpid. The lixiviums of the feveral plants are very differently acrid to the tafte, though made exactly in the fame manner and proportion, and thofe of fome plants are not acrid at all ■ that of ftrawberry leaves has fcarce any tafte ; that of the barba caprse, inftcad of an acrid tafte, has a fweet one • and the lixivium of mother of thyme has no tafte, by which it can be diftinguifhed from fair water: the lixiviums of pimpernel, dill, and ftrawberry leaves, have a fulphureous fmell ; thofe of mod other plants are wholly fcentlefs. Acf. Petropol. Vol. 4. p. 2H9.

Salts of metals. See the article Metal.

Salt of milk. See Milk.

Mineral Salt. It has been for many ages a conftant opinion among the chemiffs, that minerals contain no volatile fait.

SAL

Mr. Romberg, however, found the means of preparing an acid mineral Jolt, in a dry form and volatile. This would diflblve in fpirit of wine, and that folution being thrown on marble, fermented, and diflblved it in the manner of aqua fortis.

All the world knows that many mineral fubftances contain an acid, and th.it this is ealily raifed in diftillation, and therefore is very volatile ; but as this could never before be feparated, otherwife than in a liquid form, they efteemed it fomething of a peculiar nature, and called it an acid mine- ral fpirit, banilhing the word fait from its name. But Mr. Homberg found, that if the acid fpirit of any mineral was fo embarrafled in the particles of fome metal, as that it ceafed to be fluid, that metal was always confiderably in- creal'ed in weight by it ; and that if afterwards all the acid which had been added to it were again feparated from it, there would remain a volatile fait in a dry form, and that this fait if diflblved in fpirit of wine, or in common water, made an acid liquor, which would dih'blve all alkalies with an ebullition : from this, he fays, it is plain, that the mi- nerals have a volatile^/, as well as the animals or plants ; which laft were alfo long fuppofed to want it, and the vola- tile fait fuppofed peculiar to the animal kingdom : from this alfo it very plainly appears, that the acid fpirits of minerals, as they are called, are in reality no other than thefe volatile falts diflblved in their own phlegm.

The method of procuring this fait may be feen in the fol- lowing inftance. Take two ounces of fine filver, diflblve it in five ounces of fpirit of nitre ; pour this folution, while hot, into a pint of river-water, in which there has been before diflblved as much fea fait as it can contain, the filver will precipitate itfelf in form of white fcales. Wafh this precipitate till it is infipid to the tafte, and then dry it ; it will, when perfcflly dried, weigh two ounces and an half.

After this calcine in an iron vellel over a ftrong fire two or three pounds of fine tin, in which there is no mixture of any other metal. Take of this calx of tin well dried an ounce and half, mix this carefully with the two ounces and half of the calx of filver, perfedly dry alfo : put the mix- ture into a mattafs, of which two thirds fhall remain empty ; expofe this matrafs to the naked fire, with its neck turned downwards, there will run into the neck of the matrafs a black matter, which will immediately fix itfelf into a hard ftone of a brown colour, this will weigh about an ounce and half ; this ftone is the calx of tin diflblved by the acids, which remain in the calx of filver ; and the caput mortuum, at the bottom of the matrafs, will be found to be the filver now diverted of thofe fain, which it had carried with it from its diflblvent in the precipitation. This may be run into a mafs by the copel, and no part of it will be loft. Beat this brown ftone to powder, let the powder he perfeci- ly dry j then put it into a double vefiel, fublime it according to art, and the refult of the operation will be half an ounce of a volatile fait ; this is to be reflified by re-fublim- ing it two or three times over a very gentle fire, and it will then be a volatile and mineral fait, perfectly dry, of afine white colour and tranfparent. The caput moituum of this fubli- mation is the calx of tin. Mem. Acad. Par. 1692. Salt of mineral -waters. See the articleHALCRYPTIUM. Pine Salt. See the article Pine. Salts of plants. See the article Plant. Sedative Salt, a name given by the modern chemifts to a fait, of the virtues of which they boaft much. Thofe who firft defcribed it gave the procefs for making it in a very enigmatical manner; and their fucceflbrs invented many different ways of preparing it. The truth is, that all mix- tures of borax with the vitriolic acids furnifh us with d.feda- tivefalt, as do alfo the mixtures of borax with fpirit of nitre, or of fea fait.

Becher firft gave the enigmatic account of it, which Hom- berg traced to its origin, and found the way of making it with thevitriolic, as Lemery did with the other acids. This fait is formed by fublimation, and is a congeries of faline flow- ers, not a little approaching to flowers of benjamin. Thefe flowers are fo light and fine, that they fwim upon water, and will not diflblve in it unlefs it be made warm. 'The f dative fait is a oeife&fal falfus ; it makes no altera- tion in the colour of the juice of violets, and has no fenfible effect on the folution of corrofive fublimate, or on a folution of mercury in fpirit of nitre for a long time ; but it finally precipitates a yellow powder from it as the borax does ; there is this difference, however, between this precipitate, and that formed by crude borax, that the powder precipitated by the fedative fait, does not as the other become white on wafhing with large quantities of water. Thefe experi- ments fhew this fait to be wholly analogous to tartarum vi- triolatum, or to the Glauber's/?//; in its effects. When the compofition of which this fait is to be made is placed on the fire, there arife different liquors before the fait, appears ; the firft is a phlegm of a fattifh complexion, and with the fmell of foap ; this is fucceeded by a turbid white liquor, along with which there arife fome of the firft flc-w-

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