Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/396

 SAL

the feeds will ripen and become bluifh after cutting, which will be much better than the letting them be loft by waiting till they ripen upon the ftalks in bad weather. The faint foin for feed mull: never be cut in the heat of the day, for then it will dry too fail as it falls, and much of the feed will be loft. It is beft for the mowers to begin at day- break, and to leave off as foon as the fun has any power, going to work again in the cool of the evening. If the plant be dry at the time of cutting, it may be immediately made up into little cocks ; but if not, it muft be made hay of, only obferving never to turn it while the fun is hot upon it : unlefs there happen rain it is fcarce neceflary to turn the fwarths at all ; and when this is done, it muft be done very carefully, that the ears be not fliaken.

There are two ways of thrafhing this plant ; the one on the field, the other in the barn. Tbe firft can only be done in very fine weather, and while the fun mines warmly upon the' field. The middle of the day is the only time for this, and the method is to fpread a large fheet, and peg it down at the corners, and in this thrafh the plants from the cocks by fmall parcels at a time. The ftraw is to be feparated from the feed, and made up into ricks ; and this is good food for horfes and other cattle, and the feed, isc. is to be col- lected, and afterwards winnowed, to feparate the chart. If the feed have been wetted in the time of thrafhing or ly- ing in the ear, it may be put up immediately ; but if it have been thrafhed and winnowed dry, it will ferment and fpoil if laid together too foon. The common way of managing it is by fpreading it in a malt-houfe, or on a bam floor,

' but in fpite of this it will often heat and fpoil ; the beft way of all is to fpread a layer of ftraw, and on this fprinkle a layer of the feeds, then cover thefe with another layer of ftraw, and this with more feeds, and fo on, till the heap is raifed fix or feven feet high. The feed will thus be kept cool, and in fpring it may be eafily feparated from the ftraw, and will be as frefh as if juft thrafhed ; if this be fown, not one feed in twenty will fail of coming up. When the wea- ther is not fine enough to give opportunity to the thrafhin_ the faint foin ill the field, it muft be very carefully carried into the barn with fheets at the bottom of the carts, other- wife a great quantity of the feed will be loft in the way, Tull's Hufbandry, p. 90.

SAKER, in the manege, the fame with dock. See Dock.

SAL, fait {Cycl.) — Seethe article Salt.

Sal, in the hiftory of the gems, a term ufed by Pliny and the antients, to fignify a defect or flaw, which took off very much from the value of the gem. Martial having occafion to mention this fort of blemifh, in cryftal, calls it nitrum inftead of fal. Etturbata levi qucjlus cryjlallina nitro. The critics have fornetimes changed this word nitro, to vitro, and others have made the confufion yet greater, by fuppofing that the poet did not mean rock cryftal but crystalline glafs : but thefe are all errors. It is plain, by what Pliny and others have faid on the fame fubject, that the author means here the fame that others do by the word fal. This was a dufky and dufty foulnefs, feemingly com- pofed of a quantity of faline particles, (hooting into their forms within the body of the cryftal. The gems in general were fubject to this blemifh ; and we find, in particular, that the emerald was frequently debafed by it. It is found at this time, indeed, that cryftal is much more fubject to it than any of the gems ; but, as the Romans called all the green cryftals found in the copper mines of Cyprus by the name of emeralds, it is eafy to conceive, that the emerald, as they underftood the word, muft be fre- quently fubject to it. The poets ufing the word nitrum in- ftead of fulh not wonderful, for the Greeks called common fait hahnitrum, fo that the words feem almoft fynonymous.

Sal Mgyfti, in natural hiftory, a name given by Hippocrates- and many other of the old writers, to the natrum of the an- tients, called alfo nitrum by fome, though very different from our nitre. It had the name natrum from natrium, or nitrium. the name of a city of /Egypt ; and therefore this, as well as the name ufed by Hippocrates, ftood for Egyptian fait.

Sal ammoniac, or ar maniac. See Armoniac, Cycl.

The fubftance known by the antients, under this denom nation, was very different from the fait we now call by this name. It was indeed no other than a particular appearance of the muria, or common alimentary fait, in a ftriated form. We have common fait of this very form now in fome parts of the world, but though with us it is fcarce, with them it was very frequent, and was in common ufe, and efteemed the very belt kind of fait for the ufe of the table. Diofcorides is extremely accurate and exprefs in his account of it, and when he has reckoned up the various properties and ufes of common fait, he defcribes the feveral forts of it, and parti- cularly this ftriated one among them, which, he fays, was the very beft of all the kinds ; yet it feems owing to the dc- (cription of this author, that the common errors about thi fait have arifen ; for he fays that it was foflile, and com- pofed of ftrait regular fibres. And after writers finding no fait of the common alimentary kind, anfwering to thefe characters, and perceiving that the compound mafs, we call fal armoniac, was of this ftructure and appearance, made no 3

SAL

hefitation to determine this to be the fait called fal ammonia' cum by the antients, not confidering the incongruity of the characters of that fait to their accounts, or the impoffibility of its ever being ufed at table as common fait. Hill's Hift. of FofT. p. 384.

The fal ammoniac of the moderns may be eafily prepared in the following manner : take four ounces of common vo- latile fait of ox bone, faturate it with ftrong fpirit of fea fait, and evaporate the fuperfluous moifture, upon which there will be found a cake of true fal armoniac left behind. This is an experiment which regards both philofophical and technical chemiftry, as it fhews that odours may depend upon the mechanical ftructure and texture of bodies ; and leads to a cheap way of making fal armoniac in other coun- tries, as well as in the Levant. The volatile fait here em- ployed has a very quick and pungent odour; fo Jikewife, though in a lefs degree, has the fpirit of fait ; but thefe two, upon mixing, deftroy each other's odour, fo as to leave the cake of fal armoniac fcentlefs ; but if a little of this fal ar- moniac be rubbed in a mortar with fait of tartar, or any other fixed alkali, this lays hold of the acid of the fez fait, and leaves the volatile fait ro ftrikc the nofe as pungently as be- fore, Shaw's Lectures, p. 422.

Our own volcanos, or fubterraneous fires, which we have in the coal countries, afford us fal ammoniac. It is found flicking to the fides of the openings of thefe volcanos, in confidcrable thick crufts, under other crufts of fublimcd ful- phur. There is no foMefalt in thefe places, nor any thing elfe, that can form fal armoniac in the common way we fup- pofe it to be found in ; but it appears truly, that it proceeds only from the coal that feeds thefe fires. It is certain, that fal armoniac is fornetimes found on brick kilns, where nothing but coals and common brick clay are burnt j and as no one would fufpect it of being contained in the brick clay, there is here only the coal to afford it. The common coal flate of thofe counties alfo contains alum, fulphur, and fal armoniac ; for alum may be drawn from it by the common operations ; and when it is burnt, as it frequently is there for hardening the coal ways, both brimftone and fal ar?noniac are found in the heaps in feveral places.

The fal armoniac found in the openings of the burning moun- tains, particularly mount /Etna, is evidently the fame in all refpects with ours ; and even this alfo may, for ought we know, be formed of coals, of which the inacceflible bow- els of that mountain may contain great ftores ; though none have been found rifing near enough to the furface to be dug for ufe. Other bitumens alfo may poflibly afford this fait on burning as well as coal, and it is not to be doubt- ed but many fuch are to be found in the earth thereabouts. The fait on the fides of the mouths of mount ./Etna is found in large and thick cakes, and in dry weather may be col- lected in vaff. quantities, and poflibly a great part of what the Venetians fell into other parts of Europe may be from thefe places. Either this fait, or that of our own volcanos, may be ufed in all the proccfles of chemiftry, with the fame fuccefs as other fal armoniac. It is of itfelf grey and coarfe, but on mixing it with lime, and wetting them, a volatile fpirit is raifed ; and on fubliming a mixture of it with pot- ato, a dry and white volatile fait is obtained. If fome fpirit of wine be added to the mixture offal armoniac and pot-afh, more of the volatile fait will be produced than any other way. Phil. Tranf. N° 1 30.

We are well aflured that this fait is a concrete, the acid of which is that of fea fait, and its alkali, a volatile uri- nous one; both of which are found in dung burnt and raifed into foot.

If there is occafion to feparate the acid of fez. fait from fal ammoniac, there need only be ufed the common vitriolic acid, which being well known to be ftronger than that of fea. fait, it divetts that ac;d of its alkali by its fuperior power, and it becomes the bafis of a new concrete fait with this acid, while the acid of fea fait now freed and feparated may be drawn off pure by diftillation.

If on the other hand it were required to draw from fal am' maniac its volatile alkali, the fubfhmces to be employed to this purpofe are fuch alkalies as act upon the acid of the fen fait, ablbrbing and retaining it; the volatile alkali be- comes freed., and rifes with a very fmall heat. This alkali thus raifed appears in two different forms, the one a liquid, which is called fpirit of fal ammoniac, the other a dry one, which is called the fublimedyo// of fal ammoniac; and though thefe are fornetimes obtained feparate, yet in fome opera- tions they are in part of the one and in part of the other kind. This is well explained by Mr. du Hamel in his courfe of experiments on this fubftance. Mem. Acad. Scien. Par. 1735.

As the adding an alkali is the way to feparate this natural volatile alkali from fal ammoniac, the more powerful that added alkali is, the better may it be expected to perform its effect^ Chalk, lime, fait of tartar, and pot-aihes, have all been in common ufe to this purpofe, and all except the lime give the volatile alkali in a dry form, which is no wonder, fince thefe are all naturally dry bodies before the operation ; but there is one circumftance in thefe operations very worthy

regard,