Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/651

 T I N

TIN

lowed, it is no wonder that the two metals are eafily brought together by the mediation of tha> principle. Memoirs Acad, bcienc. Par. 1737.

Mr. Cramer gives the praflical rules of feparating filver from Tin, thus : Divide one centner of Tin into two equal parts ; put each of thefe into a feparate teft, and add to each fixteen centners of granulated lead, and one of copper; put the whole under the muffle, and make a very ftrong fire ; the Tin will be calcined immediately, and will fwim upon the lead. Then diminish the fire a little, till the afhes of the Tin that fwim upon the furface do no longer fparkle; when you fees this, add with a ladle two centners of glafs of lead to each teft, in fuch manner that it may be fpread wide over the whole furface of the rejected calx; the calx will then change its form of powder into that of glafs ; then increafe the fire to its higheft degree, ftir up the whole with an iron rod made warm; and when the fcorification is perfected, pour out the mats into a mould ; the fcoiije being feparated, put both the regulus's. into two coppels well heated ; and into a third put fixteen centners of lead, and one of the fame copper ufed in the procefs ; examine all thefe beads after the cop- pelling is over ; if the two firtt weigh exaftly alike, 'tis a proof the procefs has been well performed, and fabftraciing the weight of the bead, feparated from the third pan, from the joint weight of the other two, the remainder is the weight of the pure filver contained in the quantity of Tin which was examined. Cramer's Art of Allaying, p. 228. Tin eafily melts with filver, gold,' or copper ; but when they are mixt with it in equal or lefs quantity, it renders them extremely brittle. Silver is peculiarly fufceptible of this mif- chief, and becomes almoll as brittle as glafs, by the admix- ture of a very fmall quantity of Tin. Much greater quantities of Tin, however, in fome metallic mafl'cs, leaves them ftill pliant in fome degree. Ten parts of Tin, and one part of copper, melted together, make a mats more rigid than pure Tin, hut ftill fomewhat tractable ; and it is by this artifice, that vefiels and utenfils are made of tin, and yet are found confiderably hard.

If to ten parts of Tin, and one part of copper, a little zink or brafs be added, it makes a very fonorous metal, but brittle. This is fometimes the mixture ufed as bell-metal, and cannons are in fome places caft of it. Lead becomes fomewhat more rigid, or lefs duflile than before, by being mixed with 27s ; but of all the metals it fuffers the leaft by the mixture. If filings, or thin plates of iron, be made red hot in a cruci- ble, and a double quantity of Tin put to them in a great fire, the whole will run into a brittle white rcgulus, which will yield to the magnet.

The vapours of Tin are very noxious to filver, gold, and copper, rendering them all brittle ; nay, if only a little Tin be put into the fire, in which they are to be melted, they become brittle as foon as red-hot, and will break like glafs under the hammer.

This metal, expofed to the focus of a powerful burning-tdafs melts, and emits a thick white fume, and, if held there a long time, wholly diffipates itfelf in that fume. If, on the contrary, this metal be fufed in a coppel by the fame heat, it fumes confiderably, and its furface becomes covered with a white calx, which greatly rarities and expands, and there fi- nally appear numbers of cryilalline and bright ftria; like needles in that calx. If this be continued in the focus on a piece of free-Hone, thefe cryftals ceafe to fume, and remain fixed while the ftone itfelf melts and runs. And in the coppel there is ufually a part of thefe run into a reddifh matter, re- fembling a fort of enamel. II the calx of Tin (that is,' Tin reduced to a grey powder, by being divefted of a part of its oil in the fire) be expofed to the focus of the burning-glafs, it fumes more than plain Tin, and is very foon transformed into cryilalline ftria:, or needles. And if thefe are again expofed to the fame focus, placed on a piece of charcoal, they readily melt, and again aftume the form of common Tin. The char- coal, in this cafe, furnifhes to the calx of Tin that oily matter which the fire had divefted it of; and it is well known, that if the calx of Tin be made red hot in a crucible, and any fatty or inflammable matter be added to it, it immediately refumes the form of Tin again ; this reduftion is wholly upon the fame principle with the other, the oil of charcoal doing in the firft, what the fat does in the laft.

It appears, upon the whole, that Tin contains an oily matter, which is eafily driven off by fire, and very eafily received again on the mixture of any fat fubftance ; that the earthy mat- ter, which is the bafis of Tin, is of a cryltalline nature, and very hard to fufe, fince no common fire can vitrify Tin alone ; and even the focus of the moft powerful buniing-glafs does it but with great difficulty, and imperfedlly ; this femi-vitrifica- tion is what throws the calx into needles, whereas were it per- fect, the whole would be one uniform mafs, Mem. Acad. Par. 1709. Tin, in medicine, though greatly celebrated by the writers of many pall ages, is not much efteemed at prefent. It is laid to be good in convulfions, epilepfies, and the madnefs arifing from the bite of a mad dog. Its preparations are thefe : 1. Stmmum pulverization, or powdered Tin. 2. Sal Jovis, or

fait of 27/*. 3. Diaphoreticum JoviaU, or ailtiheflic of Po- tenus. 4. Aurum muflvum, or, as it is commonly called, mojauum, mofaic gold.

The powder of Tin is faid to be a good remedy againft worms, particularly of the flat kind, whirl often elude'the force of other medicines. See the article Worm.

Tr n is alfo a word ufed by fome of the chemical writers to ex- prefs fulphur.

Tim Floors, a contrivance ufed by our hufbandmen who propa- gate hops, to dry them after the gathering. The common way of doing this, is either on a hair-cloth on a malt-kiln, or elfe by the ooft. See the article Oost. In both thofe ways, however, the hops fuffer very much ; the belt way is by the Tin floor. It is thus done: Let a fquare brick room be built, with a door on one fide, and a long fire- place of a foot wide in the middle, reaching almoll acrofs it; let holes he made at the fides of this fire-place, to let out the heat into the room ; and at the height of five foot above this let a floor be made of laths of an inch thick, laid lattice-wife. Let this be covered with great plates of double Tin, taking care that the joinings of the Tin be well foldcred, and lie upon the laths, not over the interftices, which may be about four inches wide. Let a row of boards be fitted round the edge of this floor, to keep the hops from falling off, then lay on a covering of hops of a foot thick ; then make a fmall fire of charcoal in the mouth of the fire-place, and the hops will dry very quick and very regularly. They may be continually ftirred about while drying, and when enough, a part of the boarded edge of the kiln may be taken down, and the dried parcel thruft out, and a frefh parcel laid on in their place. A very fmall quantity of fuel is fufficient in this way, and any fuel will do, for the fmoke never comes at the hops. There is a very great improvement ftill upon this method of drying hops, ufed by fome people ; this is the making a wooden co- ver, of the fize of the Tin floor ; this is covered with plates of Tin nailed on, and is fufpended over the kiln in fuch a man- ner, that it may be let down at pleafure, when the lower parts of the hops are dry. This is to be let down within ten inches of their furface, and there it acls as a reverberatory, and drives back the heat on the upper ones, fo that they are dried as foon as the lower ones. Thus all the trouble of turning is faved, and the hops are much better dried than in any other way. Mortimer's Hulbandry, p. 186.

Tlh Hatch, in mining, a term ufed by the people of Cornwall, to exprefs the opening into a 27b mine. They alfo call it a Tm-Jbaft.

They make feveral openings in the fides of the hills where they fufpeiSl veins of ore to be. All thefe, except that which opens on the head of the mine, are called ej/ay- hatches ; but that which does fo, is made their entrance afterwards, and changes its name to that of the Tin-hatch.

Tin Ore. Tie firft procefs toward the feparating the metal from this ore, is the roafting it, which the affivyer performs in this manner: Put fix centners of Tin ore in coarfe powder in a teft, under a muffle made thoroughly red hot, (hutting firft the veflel for a few minutes, and then opening it. If the fire is pretty ftrong, the volatile part will be feen expelled in a thick white fmoak, fmelling like garlic. When this is over, take out the tell, and when the ore is cold, beat it to powder, and roaft it again in a fomewhat ftronger fire, till it exhales no more arfenic, which may be known by putting upon the teft, whenjuft taken from the fire, a thick cold plate of iron, which will be covered on its under furface with a fmall whitifh cloud, if the ore yet exhales any arfenic. Cramer's Art of

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When the roafting is thus finifhed, the ore may be run into malleable 27s in the common manner, as the common lead ore is, only with this caution, that the fire in the operation be carried as foon as poffible to the higheft degree that is ne j ceffaryhere, and the veflel taken out of the fire, as foon as the operation is judged to be finifhed.

Tin Plates, an article of manufacture very common among us, and vulgarly called Tin. It is iron plated over with Tin. The French call it fcr blanc, white iron, as we fometimes do in England. It was once known under a diftincl name, latin. See the article Latin.

TINA, a name given by the old medical writers to a bath made of a ftrong decoction of many carminative ingredients, to be ufed in the colic.

TINCA, the Tench. See the article Tench.

Tinca Marina, the Sea-Tench, in zoology, a name given by Ibme authors to the common turdus, called in Englifh, the ivrajfe. Willugbbfs Hilt. Pifc. p. 320. See the article Wrasse.

TINCTURE (Cycl.) — A general rule for the properly mak- ing light Tinftures may be taken from the following bitter. T ake half an ounce of Seville orange-peel fhaved thin, half a dram of gentian-root thin fiiced, a fcruple of the tops of Roman wormwood, half a dram of cardamum-feeds, and the fame quantity of cochineal, each of them lightly bruifed ; put thefe ingredients into a pint of French brandy, let them fteep for one night, and filter the liquor the next morning, and thus vou have a fine light bitter.

Thefe