Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/560

 S T I

S T I

nation, in the fuccefs of the procefs, was not occafioncd by any difference in the fire, but by the different nature of the matter employed. The crude ore of antimony fometimes be- ing mixed with a white argillaceous earth, and fometimes free from this admixture ; he found, that when it had this white earth in any great proportion, it never tailed to yield this acid liquor ; and that when it had none of it, it never could be made to yield a drop of acid ; and confequently, that this was not an acid extracted from antimony, but merely frorri the earth, as common pipe-clay, or any of our ar- gillaceous earths, will yield an acid by means of a ftrong fire.

This Hq*'.or had therefore been very improperly called the vinegar of antimony ; and it is evident, thatwhatever.acid antimony contains, mult be of the nature of fp.irit of fulphur, fince fulphur fo greatly abounds in the compofition of that mineral, and its fulphur is wholly the fame with the common brimftone. Whatever acid, therefore, of this kind could be produced, mult be of the nature of that collected from the fumes of burning fulphur ; and, even though it were pro- duced from antimony, could have nothing of the nature of antimony la it, fince it would be wholly the produce of the common fulphur in that mineral, and not of the reguline part, which alone is properly antimony. Experiment alio proves the truth of this opinion, the acid of antimony, truly feparated from it, being no way different, in any particular, from that of crude fulphur.

There are feveral ways by which it may be made, but the fol- lowing feems the eafieftand moft familiar. Powder crudea«/i- mony very fine, lay it in an earthen dim not glazed, and of a confiderable width at the top ; cover this difh with an earthen pot, with the bottom taken out, and fit to this three earthen alu- dels, and cover the mouth of the uppermoft aludel with a large glafs bell; the edges of which muff be fuftained about a quar- ter of an inch above a veffel of water, kept fo hot, as to fumi- gate the mfi.de of the bell ; the water that runs down from the bell, will be received again into the veffel of water. In the middle of the earthen pot, which covers the difh of antimony, there muff be a hole, large enough to admit the handle of an iron ladle, or fame fuch other inftrument, to itir about the antimony. The fire being made under the earthen difh, and continued a proper time, there will be found the flowers of antimony in the aludels, a little acid li- quor in the water of the veflel kept under the bell, and the antimony will be found calcined in the difh. It is but little acid that can be obtained in this manner, but then it is afTuredly the pure acid of the fulphur of antimony. Sometimes this method furnifhes alfo little or no acid, but this depends on the care of the operator, and the tempera- ture of the air ; for the colder and moiffer the feafon is, the more acid will be obtained, and the hotter and drier it is,

, the lefs. The operation, whenever Co perfect, is however of little value, the acid being every way the fame with that of common fulphur, Mem. Acad. Par. 1700.

Jnfufon rf Antimony. Mr. Romberg being well affured, that water was a menffruum capable of diffolving all the me- tals., if properly applied, ufed it, in feveral different man- ners, in his analyfis of antimony. He made an infufon of antimony in water, putting into feveral glafs veffels crude an- timony, coarfely powdered, five pounds into each veflel, and to each of thefe quantities he added two pints of rain water ; after the antimony had ffood thus for fix months, the feveral parcels were ufed on different occafions, one only excepted, which had been forgotten, and had at length flood two winters and a fummer : having at length found this veffel, he obferved that its infide was every where coated over with configurations of leaves ; he at firft fuppofed this to be ow- ing to fome falts of the antimony, which had been diffolved in the water, and had afterwards cryftallized themfelves in this manner, as the butter of antimony is fometimes known to do in fublimation; but on rubbing the fides of the vefTel with a finger, and afterwards fcraping them with a knife, he found that they were covered with a yellowifh pellicle, without the leaft appearance of fait, and that the configura- tions of the leaves were not raifed upon this pellicle, but funk, as if graved by a tool. The water taffed fome what acid, and being tried on turnfol, and on different metallic folutions, it turned the turnfol to a light red, and turned a folution of filver white ; whence it appeared to be an acid, and of the nature of that of fea-falt. The funfhine had turned this water fower, had made it act upon the anti- mony, and take up a part of its fait. This fait, in the win- ter, was probably afterwards concreted into the figures of leaves, formed upon the mud depofited by the water on th< fides of the veffel ; and thefe falts being afterwards diffolved again in fome hotter weather, had eaten their way into this fediment of mud, in the form of the leaves', Ifc. in which they had concreted. Mem. Acad. Par. 1693. Texture of St ibivm. Monfieurde Reaumur gives the following account of the contexture of antimony, or fiibium. Nothing is more common, than to obferve on the furface of broken antimony long and fliining needles, as it were; and that antimony, on which thefe are moft diftinct and vifible, is efteemed the beft. Sometimes thefe ftrcaks are ranged

with fo much order, and branch out fo regularly in certain directions, that thofe who are ever fo converfant with it* cannot but admire its beauty. The figures of the cortftitu- ent molecules of this mineral may poffibly contribute fome- thing to the formation of thefe needles* but the texture,, and configuration of the conftituent parts, will not alone adcount for the difpofition of thefe ftreaks, and their arrangements, in regard to one another; fince upon breaking different lumps of the fame antimony, and thofe of the fame ihapc, we frequently obferve quite different configurations of the needles. Let us take, for inftance, equal jnafles.of atitwiotiy of a regular conic figure, thefe being moft frequent, frorri the ihape of the veflel they cool in, which refembles a funnel, or inverted : cone; let. feveral of thefe conical .mafles?:be broken into different parts, and we (hall fee the needles, in very different directions in thefe feveral parts. In one of thefe mafl.es, from a certain height, we may ob- ferve all thefe needles directed to the point of the eone;. in a piece taken from a little higher, the needles fhall be hori ■ zontal, or nearly perpendicular to the former; above thefe we fhall find others, which fometimes direct themfelves to- ward fome point in the bafe of the cone, and fometimes form themfelves into different cones with their feveral fum- mits.

In another of thefe maffes we fhall. not find the needles dif- pofed into a horizontal direction, but running into fmall conical parcels, in directions quite reverfe one to another; , that is, fome of them fhall have their fummits toward the bafe of the cone, and others toward its apex. In fome lumps alfo we fhall difcover needles every where, and in others no where at all ; and often the needles are found in one part of the lump, with no appearance of them in the others. Some- times alfo we fhall find the infide of a mafs regularly difpofed into cones, though the outfide is of no fuch figure, for the internal cones have no dependance upon the external figure of the mafs ; and fometimes the needles are difpofed alon<* the fides of the cone, and their direction feems to follow the fides of the veffel in which they were fixed. Notwith- flanding, however, all thefe varieties in form, the caufe of all the appearances is wholly the fame, and is no other than that refrigeration, by which the mafs is changed from a fluid into a folid ftate ; and to the progrefs of this the needles plainly owe their different directions.

All melted metals cool firft at the tops and fides, and thence by degrees through the whole body of the mafs : the parti- cles at the fides'and top, which firft cool, becoming fixe to thofe which are neareft them, affix thofe, and they are the next that cool, and fo on, in fucceffive order; now molecu- lar, of whatever fhape, thus affixed fucceflively to each other, form a kind of threads or needles, the feveral directions of which fhew the order in which the refrigeration has been carried on.

If the crucible, or other veffel, in which the melted antimony is fuffered to cool, were in the fhape of a hollow bowl ; if its fides were every where equally thick, and equally- warm, and acted equally upon by an air equally cold ; and if the melted fubftance were of the fame uniform nature, alfo, in all its parts, all the needles or fibres would be then fo many rays, terminating in the center of the bowl; and if .he fubftance were fuch, that its fixed particles were na- turally all of a length, we fhould find fo many concentrical beds of needles, formed by parcels of each ray, and lying at equal diftances from the center.

But fo many regular circumftances do not concur in the cooling of melted antimony ; and hence the beforementioned irregularities muft neceflarily arife. In melting antimony in conical crucibles, and fuffering it to cool in them, the needles may be determined' feveral ways, to any directions one may choofe.

If, when the crucible is taken from the fire, it be fet to cool upon fome cold body, the confequence is, that the bottom and top of the antimony muft cool firft, and the nee- dles will be found difpofed into two cones, the one having its bafe at the apex, and the other at the bafe of the large, or general cone : but if the crucible be fet on burning coals, and the furface of the antimony covered with more coals, then the fides muft cool firft, and the needles will be found running horizontally, or forming themfelves into horizontal cones : the touching the fides of the crucible alfo, at 'times, with a wet cloth, and by that means forcing the melted matter to cool firft in fuch particular places, will 'give cones of nee- dles directed horizontally, and having their bafes at thofe fpots of the crucible fo forcibly cooled. Not unfrequently there is found a hollow in the midft of a conical mafs of antimony, and in that cafe there are ever found needles proceeding in different directions from the fides of that cavity inwards, as they, when cooled, became of the fame nature wiih the fides of the veflel, and acted on the enclofed mafs in ;he very fame manner. To procure the needhs perfect and fine, the antimony muft be fuffered to cool gradually, for, if it cool too faff, one molecula becomes fixed before it can be adapted to the end of another, and the whole is a confufed mafs ; and the fame happens alfo if it cool too flowly ; for then the particles of

fire