I R O
Ori expofihg a piece of Iron of a dram weight to the fociis of the great burning-glafs, it became immediately red-hot ; then
' its fiirface was covered with a blackifh fcum, looking like pitch or bitumen. If the Iron be taken away in this ftate, this black matter is fourid to have formed a thin cruft which co- vers it, and eafily falls off on ffriking on the backfide of the
<Iron j and the furfacc of the Iron, which was covered by it, appears whiter than this metal ufually does. This covering is, according to Mr. Homberg, a part of the oily matter ot Iron, which always feparates itfelf from that metal when it is about to melt, and remains fome time before it is evapo- rated. If the piece of Iron be continued longer in the focus, on a piece of charcoal, it foon perfectly melts, and throws out very bright fparks ; thefe are very numerous, and fome- times are difcharged to a foot diftance. If thefe fparks are caught upon paper, they appear upon examination to be fo many globular particles of Iron, and are for the moft part hollow. If the Iron be continued yet longer in the focus, it diffipates intirely in form of thefe fparks, and nothing re- mains of it.
This fparkling of the Iron appears to be wholly owing to the fulphureous part of the charcoal acting upon the oily part of the Iron ; for if it at any time happens that the furfaces are feparated by a bed ®f allies, the Iron then ceaies to fparkle, and remains iii a quirt ftate of fufion ; but if by any acci- dent the bed of allies is difcompofed, and the Iron becomes touched again by the charcoal, it immediately fparkles as before. The afhes are fometimes vitrified by the heat, and then they either mix among the melted metal, and make to- gether a fort of half vitrified mafs, or elfe the glaffy matter of the afhes iwims on the furfacc of the melted Iron in round globules ; thefe are fometimes clear and transparent, fome- times opake and obfeure, according as they contain more or lefs of the metal. If after the melted Iron has been fuffered to cool upon the charcoal, it be again expofed to the focus of the glafs upon a piece of ftone, it then will fparkle very violently, and wholly diflipate itfelf, which it otherwife would not have done, if it had not been before fufed upon the char- coal.
If fteel and Iron be expofed together to the focus of the glafs upon a piece of ftone, they both become red-hot and melt, but never fparkle ; they emit large fumes, and the metal becomes thin like oil, and if taken away in this ftate, they fi%, when cold, into regulus's ufually of a ftriated texture. Thefe metals would be vitrified in a little more time in the focus, but the matter which they are laid upon vitrifies alfo, and by that means there is a confufion of the two fubftances.
- The regulus before mentioned is a fort of half vitrified mat-
• ter ; it is very brittle, and of an obfeure dufky brown, and is no longer in the ftate of Iron ; but as it has been reduced to this ftate merely by depriving it of its oil or fulphur, it
■ may be again reftored to its ductility and true metalline ftate, by giving it again a fulphureous . matter of the fame kind. This may be done by laying it in the focus again upon a piece of charcoal, which will reftore its oil to it : in this cafe it melts readily, and remains a long time in fufion without fparkling, but at length it begins to fparkle as common Iron ; and if taken away at that time, it is found to be common Iron again, only fome what whiter and more compact than before. Mem. Acad. Par. 1709.
It appears from the whole, that Iron contains an oil or ful- phureous principle, which is what renders it bright, mallea- . ble, and fufible i that this oil 13 carried oft" from the metal by the fun's heat, when it is held fome time in fufion, nay, and that this oil'is even carried off in fome degree by a com- mon fire, which though not capable of melting Iron, yet reduces its furface in large pieces into a reddifh ruft. The - metal diverted of this oil by the fun, appears a reguline mat- ter, not unlike antimony in colour, and fecms a half vitrified fubftance ; and there feems no doubt but that this would be perfectly vitrified, if there were any way of holding it a fufff- cient time in the focus, without melting the fubftances . alfo on which it is fupported. This glafly, or reguline mat- ter requires only a fmall quantity of oil to be reftored to its priftine ftate of metal, and it readily receives this oily matter from charcoal ; whence it feems no rafh inference • that the oil of charcoal, and that of Iron, are fubftances not
■ very different in their nature, fince the one can thus replace the other ; but there is evidently fome difference, fince the Iron filled with the oil of charcoal fparkles in this trial ; whereas common Iron does not fo till laid upon charcoal and melted on it, in which ftate it probably lofes fome of its own fulphurs, which are replaced from the charcoal.
. Of all the metals Irm is the only one which fparkles in the focus of the burning-glafs, and this is probably owino- to the prevalence of a vitriolic fait in it, which is very greedy of
■ fulphurs ; and to this alfo it is probably owing that Iron con- fumes the charcoal on which it is fufed, much more quickly
- than any other metal. Id. ibid.
Iron, in medicine, is faid to have greater virtues than any of the other metals, which is not to be wondered at, as being am t nly one that [s m a manner fohrble in the human body. All the other metals, whether hard or foft, poifonous or ftlutary, nay, even fluid mercury itfelf,. fwallowed in their
1RO.
crude ftate, pafs out of the body again unaltered • but this :$ not the cafe with Iron, its crude filings are often taken as a medicine, and are always fo much acted upon by the juices^ as to produce confiderable effects. It is fo ealiiy wrought upon out of the body alfo by fire, and by different menltru- ums, that it becomes an aperient or aftringent, as it is dif- ferently treated ; and is, under proper management, greatly fuperior to all other medicines in chronic cafes. Its virtues internally were not unknown to the antients ; Di- ofcondes attributes an aftringency and aperiency both to it, and prefcribes it in hemorrhages. He alfo recommends its ruft, or crocus martis, in fuppreffions of the menfes ; thouo-n he on the other hand prefcribes wine or water, in which red- hot Iron had been quenched, as an aftringent in dyfenterics, diarrhoeas, and weaknefles of the ftomaeh. It feems to act in the human body principally by means of its vitriolic fait ; and if we rightly underlland the nature of that ftyptic fait, we fhall not be at a lofs to comprehend how a metal that abounds fo with it, acts in two fuch different manners, while both arife from the fame principle, though they fhew themfelves in various forms. Every preparation alfo of Iron is both aperient and aftrin- gent in degree; and the only difference between them is, that fome of them operate more ffrongly one way, fome the other. Thofe in more frequent ufe at prefent are, i.The .crude filings reduced to an impalpable powder. 2. The fait or vitriol of Iron, called fal martis. 3. The crocus martis dperiens. 4. Tinclura martis cum fpiritu fair's, 5. Flares martiaks, or flowers of Iron. 6. The vinum chalybeatum. Thefe are all accounted aperients. Among the aftringents .the two capitals ones are, 7. The crocus martis aftringens ; and 8. The tinclura antipbibyjlca, or, as it is called in the New London Difpenfatory, tiuflurafaturnina. How to gild Iron with water-gold, £>ec the article Gild- ing.
Iron Furnaces. Thefe furnaces as they are employed in run- ning the moft difficult of fufion of all metals, fo they are of all others contrived the largcft, and capable of carrying heat to the greateft degree. When they are to be ufed, they are firlt filled up to the top with coals ; and the lower part being lighted; the top, and all other parts of the fur- nace where the air could have pafTage, are doled firmly up with Iron plates laid one ever another. The confequence of .this is,, that the fire is put out, and the whole is kept in this ftate ten or twelve days. At the end of this time the furnace is opened, and the coals are found all black, without a ftnlrfe fpark of fire in any part, yet extremely hot, and reduced-to a tenth part of their quantity. When the furnace has been thus opened about a quarter of an hour, the matter begins- : to take fire of itfelf by the mere contact of the air. The firft appearance of this is very remarkable, there ariles a very bright flame from fome of the coals, which plays about their furface, and fprcads itfelf from one to another,' without the; appearance of the leaft fpark of fire in any part of any of the coals. The ore of the Iron is for the firft day put only in the middle of the furnace, and that but in fmall quantity j the next day more, and every day afterwards more and more is put on, and by degrees it is fpread over the whole furface of the furnace to the edges. This is the method of working the ore to the utmoft advantage, and with the moft dif- patch. The whole procefs for one furnace of ore is finifhed in about eight days from the time of the opening the top ; all the ufe of the firft quantity of coal, is only thoroughly to warm the fides and walls of the furnace ; and it is after this to be kept carefully fupplyed with fuel, and the ore only fpread out toward the fides as the extreme heat, moft fenfible in the center, encreafes. U too much be laid on of the ore at firft, there is always a lofs from the quantity of metal. The quantity of the coals neceffary to any given quantity of ore, differs in proportion to the advantageous or faulty ftruc- ture of the furnace. In the very beft conftructed ones, the weight of the coals and of the ore need be no more than equal. The flame which makes its way out of the bottom of the furnace, is of different colours, according to the na- ture of the ore and of the coals ; fometimes red, fometimes yellow, and fometimes green. That which ifiues out from the top of the furnace is of a red colour, and afcends in a fort of fpiral line refembling the found of diffant falls of wa- ters as it mounts up. With all the care that can be taken to heat the fides of the furnace, and to keep them hot, the middle is always greatly the hotteft, and the ore fooneft runs into metal there. Swedenlorg dc Ferro & Igni.
Iron Ore. In the Iron works in Staffordfhire, after the ore is dug, before it be fit for the furnace, they bum or calcine it on the open ground with fmall charcoal, wood, or fea coal, to make it break into fmall pieces, which will be done in three days. Plott, Nat. Hift. Staff, c. 4. n. 21. This they call annealing or fitting it fur the furnace. Howht, Collect. N° 271. See Iron Furnaces, fupra. Iron may be procured from its ore in a elbfe veflel in the following manner : Roaft for a few minutes in a teft, placed under a mufiel in a pretty ftrong fire, two centners of Iron ore grofsly powdered, that the volatile particles may be in part diffipated, and the ore foftened in cale it be too hard. i When
