Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/508

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affords a different figure, from what is produced by the na- tural cold of the air. And the former ice being thawed, and left to freeze in the fame vial, did not give the fame figures as at firft. See Boyle's Works Abridged, Vol. I. p. 1 68.

Solution, in metallurgy, is diftinguifhed into dry and moift.

) The dry folution is the blending imperceptibly a fmall quan- tity of a metal, or mineral, with a very large one of fome '

■ other body, dry, hard, and not fluid when cold. The moift folution is the distributing a body through the very mimrteft parts of an aqueous, or in great part aqueous fluid, in fuch manner, that both may turn into a fluid, to appearance, homogeneous, which goes through all filters, without being detained or feparated by them, and the fmalleft part of which, contains in it a proportionable quantity of both the men- ftruum or diffolvent, and of the diflblved body. The folu- tion of gold in aqua regia, and of filver in aqua fortis, as alfo that of any of the falts in water, are folutions of this kind. Cramer's Art of Aflaying, p. 194. In the making the feveral metallic folutiom, for the neceffary procefles in chemiftry, the operator is fub- jett to great danger in his health, from the noxious va- pours. This has been an accident complained of indeed by many, but fcarce attempted to be remedied or ob- viated by any, in a rational way, till Mr. Geoffroy,

- whofe experiments fubje£ted him greatly to the mifchief, employed his thoughts for his own fake, as well as that of the world in general, to the effectual preventing it. The diflblutions of the metals, in the corrofive acid fpirits, are thofe which fend out the moft copious and moft dan- . gerous vapours. The exhalations of quickfilver, of anti- mony, and of lead and copper, arc all in themfelves greatly hurtful, as well as the fiery vapours of fpirit of nitre, fea- falt, or vitriol ; and if either of thefe is fingly fo, how per- nicious muft they need be in thofe cafes, where two of them are joined together in fuch a manner, as that this union fends up infinitely more vapours than would otherwife arife ? in this cafe, the utmoft care is neceflary to prevent the chemift from falling a facrifice to his zeal for his disco- veries.

The common way of avoiding this danger, is by making the folution either abroad in the open air, or in a chimney ; but fometimes thefe cautions cannot be ufed, and under fome circumftances they are ineffectual. This gave occafion to Mr. Geoffroy to ufe a method, which he afterwards pro- pofes to the public, of flopping the rife of the vapours entirely, or at leaft of diminiihing them fo greatly, that they fhall be harmlefs and unperceived. All that was neceflary to this, feemed to him to be the contriving to cover the furface of the fluid with fome body, capable of retaining thofe vapours, yet not capable of difturbing the operation of the menftru- um on the metal ; and the common expreffed oils of fruits, . as the oil of olives, almonds, or the like, were found capa- ble of happily performing this effect ; and that particularly, as they would eafily receive into themfelves the acid falts which arife in the conflict. The thing which gave this gen- tleman the hint of the difcovery was, that in the boiling of fugars, honey, or the like fubftances, when there is any danger of their boiling over the veflel, the pouring in a little oil flops the fwelling. In the metallic folutiom it has the fame effect ; and that heightened by this good confequence, that by keeping in the fiery vapours of the acid, it returns them back upon the metal, and by this means does, in effect, add greatly to the power of the menftruum. This method of ufing oil has indeed three advantages, i.The preferving the operator from the injuries from the vapours. 2. The greatly moderating that violent rarefaction which is often of ill confequence. And 3. the fame quantity of the menftruum, by this means, diflblves more of the metal. The beft method of making folutions with this advantage is this : firft wet the furface of the metal to be diflblved with water, or fpirit of wine ; then pour a little water, or fpirit of wine, into the glafs in which the folution is to be made, this will prevent the oil from flicking to the furfaces of ei- ther; then put the metal into the glafs, and pour in the oil upon it; laft of all, pour on the menftruum: this being greatly heavier than the oil, will fink to the bottom and work upon the metal, while the oil perfectly covers the whole furface. There is no need to be exact as to the quan- tity of the oil, but more or lefs is to be ufed, in proportion to the greater or lefs ebullition which the mixture is expected to make.

The air-bubbles, which arife to the furface with great im- petuofity in the making of thefe filiations, are here feen to break by degrees as they enter the covering of oil, and ge- nerally are quite diffipated before they arife to the furface of it. The few of them which retain their figure till they ar- rive at the furface, there burfl and give a flight exhalation ; and one may continually fee the drops of the menftruum falling back again out of the oil into it, after being deferted

the contrary, in the common way of making folutions, the air-bubbles pufh one another up to the furface, where they form a fort of ikmn, which continually thickens by their
 * by the bubbles of air which had raifed them fo far. On

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frefh riling and fupporting one another, till it often rjfes over the top of the veffel. Thefe bubbles of air feem to be formed of fmall parcels of air extremely condenfed in >the pores of the metal, which, when the particles of it a ie f e _ paratcd for folution, find themfelves at liberty to dilute and expand, and arife to the furface in their proper form. If it be thought neceffary, in any folution which raifes a more than ordinary quantity of vapours, to prevent the fly', ing off of that fmall quantity which may efcape through the oil, there is nothing more neceflary than to pour a little fpirit of wine upon the oil ; for the acid vapours which pafs the oil will then be received in the fpirit, and will be dulci- fied in it, and inftead of a difagreeable odour, will yield only a very fweet and fafe one. Spirit of wine alone, ufed in- ftead of oil, and poured gently on the folution, has very great effects; ipfomuch, that if ufed to the folutions m fpirit of nitre, which ufually fend up very noxious and coar.fe red vapours, they by this means are made to fend up only very fine light white ones, and thofe of a very agreeable fmell ; the bubbles raifed in this cafe. are very fmall, and ufuallv burft before they arrive at the furface of the fpirit. The only objection to this method, is, that the fpirit of wine foon mixes itfelf with the menftruum, and there are fame cafes in which this may be of ill confequence to the procefs, Mem. Acad. Par. 1719. SONCHUS, fowthijlle, in botany, the name of a genus of plants, the characters of which are thefe, The flower is of the femiflofculous kind, being compofed of a number of fe- miflofcules, each ftanding upon an embryo feed, and all con- tained in a general cup, which is confiderably thick, and becomes of a conic figure when ripe. The embryos finally become feeds, winged with down, and affixed to the tha- lamus. See Tab. 1. of Botany, Clafs 13. The fpecies of 'fonchus, enumerated by Mr. Toumefort, are thefe. 1. The prickly fonchus with undivided leaves. 2. The prickly fonchus with leaves jagged in the manner of thofe of dandelion, 3. The prickly fonchus with undivided leaves, in inapt refembling thofe of the lettuce, or of dipfacus. 4. The Cretic jagged prickly fonchus, 5. The great tree prickly fonchus. 6. The great creeping fonchus, called by many the great creeping hawk-weed. 7. The fmooth fonchus with broad jagged leaves. 8. The white-flowered broad- leaved jagged fmooth fonchus. 9. The fmooth fonchus With leaves divided into numerous fine fegments. 1,0. The lefler fmooth fonchus with lefs jagged leaves, it. The fmooth narrow-leaved fonchus, 12. The narrow-leaved (^z-fonchus. 13. The fmooth fonchus with poppy leaves. Tourn. Inft.

P " 474 " r 7- \

The common fiwtmfiie is greatly recommended by authors

as a refrigerant and attenuant. It is prefcribed by many of

the old phyficians in ftranguries, and other diforders of the

urinary paffages; and is ordered externally, in cataplafms,

in all kind of inflammations.

SONTAGE, in our old writers, a tax of forty {hillings laid upon every knight's fee, according to Stow, p. 284. Blount Coxvel.

SOOT (Cycl.) — This is an excellent manure, particularly for cold lands, which have been long over-run with mofs ; but fez-coal-foot is much better for this puipole than wood-foot. They ufua'Iy allow forty bufhels to an acre, but fome lands require more. It produces an extremely fine and fweet grafs, and deftroys weeds of all kinds. Mortimer's Huf- bandry.

The chemical analyfis of foot fhews us, that it is compofed of feveral parts; 1. a fetid, oily, bitter fpirit. 2. Water. 3. A fharp volatile alkaline oily fait. 4. A fharp alkaline fat oily fpirit. 5. A fetid black bitter inflammable, and al- moft cauftic oil, mixed with an oily fait. 6. A true fal ar- moniac. And 7. a black fixed earth.

JVood-Soor has been long known as a good medicine in many cafes, but the principles upon which it acted as fuch were never well underftood, till Boerhaave gave a regular ana- lyfis of it. The directions he gives for the procefs arc thefe.

Choofe the blackeft and drieft wood-foot from the chimney of an oven, where nothing is baked but bread, and nothing burnt but vegetables ; gather this in a dry day, and fill with it a glafs retort almoft up to the neck ; clean the neck of the retort, and luting on a receiver, give a fire of a hundred and fifty degrees, and keep it up equably, a large quantity of transparent water will come over with confiderable vio- lence. When no more water will come over, cleanfe the receiver, and raifing the fire to a little above two hundred degrees, there will then come over a whitifh fat liquor; this alfo comes over with great violence, and the fire muft be gradually encreafed, till no more of this will come. Change the receiver, and raife the fire to a yet greater degree, and a yellow, copious, volatile fait will come over, and flick all over the fides of the new receiver. When no more of this fait will arife, encreafe the fire to the utmoft that fand can give, and with a heat of fuppreffion there will arife a black thick oil ; when this is all come over, and the veffels cooled, there will be found in the neck of the retort a fait, which could be raifed no higher, even by. that violent fire; and in

the