TIT

TOP

( 438 )

flruum either acid or alkaline. By fufion witha carbonated alkali it is converted to a carbonatinfoluble in water, and therefore capable of be-ing readily feparated by this fluid from themixed alkali.

Carbonat of titanium is foluble in the cold,by either of the three mineral acids moderatelydiluted, the carbonic acid efcaping at the fametime by effervefcence, but on heating thefe fo-lutions they are all decompofed, a white oxydbeing precipitated, or rather half feparating fromthe liquid fo as to make it white like milk.When the nitrat of titanium is thus heated,there is a confiderable difengagement of nitrousgas previous to its decompofition, which fhowsthat in this cafe the oxyd becomes infoluble byabforbing an additional portion of oxygen.When the muriat of titanium on the otherhand is decompofed by heat, there is a veryfenfible difengagement of oxymuriatic acid,thus fhewing that the infolubility of the oxydin this cafe is owing to its being deprived of aportion of oxygen. This Angular circumftanceis further demonftrated by the ready folubilityin muriatic acid of the oxyd that has been de-pofited from the nitrat.

The alkalies both cauflic and carbonated de-compofe the falts of titanium, throwing downa white oxyd in the one cafe, and a carbonatedoxyd in the other. The arfenic and phofphoricacids alfo throw down a white precipitate.The tartareous and oxalic acids afford a whiteprecipitate, refoluble in an additional portion ofacid. Hydrofulphuretted water occafions noturbidnefs, but an alkaline hydrofulphuret af-fords a dirty brownifh green precipitate ; the,green colour however is probably owing to aflight contamination of iron. PrufBat of potafhaffords a copious precipitate of a green colour,which, does not become blue by expofure to theair according to Vauquelin, of a grafs-greencolour mixed with brown according to Klap-roth , but of a dirty y'ellowifh brown accordingto Lowitz; a muriatic folution of the titaniumin anatafe was obferved by Vauquelin to give■with prufflat of potafh a chefnut brown preci-pitate. Tinfture of galls, or guiiic acid, throwsdown a bulky brownifh red precipitate, which,except the folution is much diluted, in a fhorttime becomes clotted like blood : thus precipi-tate when wafhed and dried greatly refemb’eskermes mineral.

If into a vial filled with muriat of titanium■there be put a flick of tin, and the vial be clofedby a ftoppcr, a faint rofe colour will fcon be•viflble in that part of the folution adjacent to

the tin, which by degrees -will deepen to an.amethyftine red, and extend through the wholeliquor. If a flick of zinc be fubftituted. to thetin, the colour of the folution will be firft violetand at length indigo-blue: this coloured liquorwhen gently warmed in a {hallow veffel in con-ta& with the air, will lofe its colour, and de-pofit a bulky white precipitate, again foluble inmuriatic acid, and apparently differing in no-thing from the original muriatic folution.

It is not known whether titanium combineswith fulphur, it may be made however to unitewith phofphorus in the following way. Mixthe phofphat of titanium with charcoal andborax, and heat the mafs ftrongly in a blaflfurnace, the refult will be a button of titaniumof a pale white colour, and metallic luftre.

Various attempts have been made by Vau-quelin to alloy titanium with the other metals,but wholly without fuccefs, where lead, arfenic,copper and fiiver, were employed, and with onlyvery dubious fuceefs, when iron was made ufeof.

Both the white oxyd and titanite in fubftance,according to Klaproth , afford when mixed withenamel flux, a flraw-yellow colour, and it ap-pears from Le Lievre, that it was ufed in theporcelain manufactory at Sevres as an ingredi-ent in the rich browns, but the difficulty ofobtaining from it an uniform tint, has at lengthoccafioned it to be abandoned.

TOADSTONE. See Trap.

TOEPFERTHON. See Clat potters’.

TOPAZ. Topas, Wern. Topaze, Hauyand Brack. Topaz of Brazil, of Saxony , andof Siberia . Occidental Topaz.

Its moll ufual colour is wine yellow of dif-ferent degrees of intenfity; it alfo occurs nearlycolourlefs, yellowifh and bluifh white, arid palefky-blue, alfo greenifh-grey, rofe-red, and peach-flower red.

It is found in mafs, difleminated, in rolledfragments, and cryftallized. Its primitive formis a ftrait prifm, with rhomboidal bafes, the al-ternate angles of which meafure 12+° and 56°.

The other varieties of cryftaliization that itprefents are the following.

x. An eight-fided prifm, the planes of whichjoin one another, forming two oppofite anglesof two others of 93 0 , and four others of161°. The prifm is terminated by tetrahedralpyramids.

2. The preceding, with the edges of theterminal pyramid that adjoin the two fmnlieftangles of the prifm very deeply truncated, fo asto form fometimes a hexahedral, and fometimes