TAR
TEL
( 409 )
water. When tartrite of potafli is added tothis fait, each in faturated folution, large crys-tals of the triple tartrite, or Rochelle fait areimmediately depofited.
A Super-Tart rite of Soda is formed by parti-ally Saturating tartareous acid with foda; andalfo by adding a ftrong acid to the faturatedtartrite, which, analogous with the cream oftartar, is lefs Soluble than the faturated com-pound, and therefore precipitates. Tartareousacid however will not form an acidulous tar-trite (at lead not vitibly) when added to thefulphat and other falts of foda, as it will withthe falts of potafli.
Tartrite of Ammonia.
This fait is formed by faturating the tartare-ous acid with ammonia or its carbonat. Itcryftaliizes readily, and is decompofed by thefixed alkalies and alkaline earths.
A Super-Tartrite of Ammonia is formed in aSimilar manner to the fuper-tartrite of foda,and with the fame exception of the acid notvifibly decompofing the other ammoniacal falts.
Earthy Tartrites.
When tartareous acid is added to any Solublefait of lime, or lime to a foluble tartareous fait,a white precipitate is produced which is TheTartrite of Lime. This earthy fait is infolublein mere water at a common temperature, but itdifTolves readily in an excefs of its own, or ofany other acid that does not decompofe it; Suchas the acetous or muriatic. It alfo is renderedfoluble in water by the addition of potafli asalready mentioned under the head of Tartriteof potafli. When heated Strongly in an openfire the whole of the acid is confumed, andcarbonat of lime remains.
Tartrite of Barytes and Strontian are formedin the fame manner as tartrite of lime. Theyare not however So infoluble in water as thisfait, and the tartrite of Strontian will even cry-stallize from its hot-faturated folution by cool-ing.
With Magnefta and Alumine this acid formsvery foluble compounds, which do not crystal-lize by evaporation, but dry up into a gummymafs.
Of all the tartrites, the cream of tartar isthe only one employed in the arts, which, withthe tartrite of potafli and Rochelle fait, is alfoufed in medicine.
Tellurium is a brittle metal , nearly as fufibleas lead, and eafily volatilizable; it burns rapidlybefore the blowpipe with a greenifh-blue flame,and is not much more than fix times as heavyas water.
§ I. Ores of Tellurium.
Tellurium has hitherto been found only in thenative metallic Slate, and therefore, properlySpeaking, there is but one fpecies; as, however,it occurs in combination, or at leail mixed, withgold and other metals in various proportions,this fpecies may conveniently be divided intothe four following fub-fpecies.
Sp. i. Native Tellurium.
i Subfp. White native Tellurium .—GediegettSylvan, Wern. Tellure natif aurifire etferrifere,Hauy. Sylvatie natif, Broch. Sylvanite, Kirw.Aurum paradoxum, or problematicum of the olderwriters.
Its colour is tin-white, paSTing into Silver-white : it occurs maflive and dilTeminated : itpofTeSTes a ftrong metallic luftre: its fracture isfoliated : it prefents fmall granular diltindt con-cretions : it is foft and Slightly ductile. Sp. gr.5.7 to 6.1.
Before the blowpipe it melts, inflames, andis for the moft part volatilized in the form of adenfe white vapour, its component parts, ac-cording to Klaproth , are
92.55 Tellurium7.2 Iron0.25 Gold
100 . .
The proportion of gold in this fubflance isliable to confiderable variation ; one Specimen,examined by Klaproth , afforded him no lefsthan 9 per cent.
It has hitherto been found only at Eatzebnv,in Tranfylvania, where it has long been workedas a gold ore; it is at prefcnt however veryfcarce. It forms veins in transition mountains,particularly gr'auwakke and transition limeltone,and is accompanied by quartz, lithomarga,iron, pyrites, blende, and galena.
It was for a long time mistaken for auriferousantimony, to which it bears a great refemblance.
2 Subfp. Grey native Tellurium.— Schnfterz ,Wern. Sylvatie graphiqtie , Broch. Tellurenatif graphique, Hauy. Aurum graphicum, ofthe older writers.
Its colour is light Steel-grey. It occurs maf-five, and crystallized in flattened tetrahedral orhexahedral prifms, either with or without te-3 *