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in a crucible lined with charcoal is reducedinto a button of moderate hardnefs with aflight metallic luftre fuperficially, but internallyblackilh and quite dull. The only action whichthe acids have on this regulus, is to reduce itto the ftate of white oxyd. Borax and phofphatof foda, when allifted by the blowpipe, diffolvethis oxyd, but receive from it no tinge ofcolour.
TARRAS. See Cements, Calcareous.
The fubilance called Tartar , is a hard, brittle,brown-red mafs, interfperfed with imperfectlycryftallized particles, which is depofited on thelides of wine-casks, during, and after fermen-tation of the grape-juice, in the form of a thickfolid crull. In this ftate it is alfo called Crudeor Rough Tartar or Argol, to diftinguifti it fromthat which is purified in the way that will beprefently mentioned.
Tartar is not furnifhed in equal quantity fromall wines, but the more coloured and ftronger-bodied wines yield the moll. Tartar has avinous and flightly acid tafte. It confifts of alarge quantity of extractive matter, fcarcelyfoluble in water, to which it owes its colour, andof a fait, quite white when pure, compofed ofacid of tartar united to a fmall portion of potafh,lefs than is required for the faturation of theacid, but which in this proportion forms adiftinCt cryftallizable fait of confiderable im-portance in feveral arts and manufactures.
This fait when pure is called Purified Tartar ,Cream of Tartar , Cryftals of Tartar , or withmore precifion, Acidulous Tartrite of Potafh , orSuper-Tartrite of Potajh. It is alfo called fimplyTartar , but it is better to confine the termTartar to the entire unpurified mafs. Tartaris not entirely a produdf of fermentation, forit is contained in the Mufi, or grape-juice, andaflifts in the procefs of fermentation and theproduction of alcohol. The fame fait in diffe-rent combinations, has alfo been found nativein fome other vegetable juices.
Crude tartar is ufed pretty largely as a fluxin the affaying of ores. As it contains bothalkali and carbonaceous matter, it afts both inaffifting the fufion of refraCtory ores, and inreducing metallic falts and oxyds. Whenheated per fe to rednefs in clofe veflels, theextractive matter and the tartareous acid bothbecome charred, and a black alkaline carbona-ceous mafs is the rel'ult. In open veflels the
a Definaretj in Journ.
charcoal burns off totally, and at laft nothingbut pure white carbonat of potalh remains.
But the greater part of the tartar is refined toextraCt the pure fait, which is performed largelyin the South of France, near Montpellier , andalfo at Venice, and 1 1 two different methods.
The Venetian is the following : a The crudetartar is firft dried in an iron boiler, with a verygentle heat and frequent ftivring, that the acidmay not be burnt, and is then pounded in ironmortars. The ground tartar is then diftributedinto wooden tubs, and boiling water pouredupon it, which difl'olves the fait, and leaves afediment which is thrown away. The clearfolution is left three days at reft, during whichtime it depofits brown ifh cryftals of tartar.The mother liquor from this operation is re-ferred, and is ufed hot in the fubfequent pro-cefs in the firft lixiviation of the tartar. Thebrowniih cryftals of tartar are then put into acopper boiler, with the mother-liquor of formerprecedes, and flowly brought to boil, by whicha faturated folution of a deep yellow wine co-lour is produced. This is clarified in thefollowing way : a workman ftands by the fide ofthe copper with a baiket of eggs, and a bucketfud of finely lifted wood afhes. He beginswith breaking one of the eggs, and putting thewhite of it only into a bowl; he beats this upwith fome of the boiling liquor, and then poursthe whole into the boiler: he then inftantlythrows in a ladle-full of the wood-allies, and ftirsup the liquor from the bottom. A brilk effer-vefcence takes place, and the furface is coveredwith a red feum, which is carefully taken offwith a perforated fkimming-difh and put afide :a fecond portion of allies is then added, and theeffervefcence and feum are renewed and treatedas before. The whole of this operation is re-peated fourteen or fifteen times, after which theliquor becomes quite clear and colourlels. Thefire is then withdrawn, and the liquor fuffered.to remain perfectly at reft for three days. Onthe fourth, a dirty white faline cruft is removedfrom the furface, and two-thirds of the liquorladed out: the cryftals on the fides are thencollefted by a ladle and walhed in the remain-ing liquor; they are thus obtained perfeftlyclean, and require no further preparation thandrying on a wicker frame. The cryftals fromthe bottom are ftill fomewhat coloured, and areeither fold as an inferior fort, or are refined againwith frefli portions of the crude tartar. Theliquor that remains in the boiler after the depo-fition of the cryftals is a cold faturated folutionThyf. tom. i, p. 67.