T 1 N
TIN
( 434 )
i
ether domellic utenfils, but its ufe is now al-moft univerfally fuperieded by pottery, whichis lighter, more ealhy kept clean, and cheaper,though lcfs durable. The name of pewterhas been given to any malleable white alloyinto which tin largely enters, and its compo-tion is fo various that hardly any two manufac-turers employ precifely the fame ingredients andin the fame proportion. The fineft kind ofpewter contains no lead whatever, but confiftsof tin with a final! alloy of antimony, andfometimes a little copper. Wallerius gives theproportions of i 2 parts of tin, i of antimony,and about T ‘ T of copper. c A very fine metal ismade of ioo parts of tin, 8 of antimony, I ofbifmuth, and 4 of copper. The ufe of thefeadditions to the tin is to harden it, and pre-ferve its wliitenefs, and this fine kind of pewtertakes a very high polifh, has a beautiful filveryluitre, and is not readily tarnifhed. Tin , witha little zinc or brafs, makes a very fine hardalloy. In all thefe fuperior kinds of pewter,the tin forms by far the greater part of themixture.
It is to be obferved that the antimony is fointimately united to the tin, that it is not vola-tilized when ftrongly heated, or only in a veryimall degree, and it is noteafily difiolved by anyweak acid, fo that there is no danger of pro-ducing the common cfFedts of this metal in em-ploying this kind of pewter. There is a na-tural limit to the ufe both of all the brittlemetals, and of copper in alloying tin, whichis the brittlenefs which they impart to thealloy when they exceed certain proportions.But it is not fo with lead, which may bemixed with tin in any proportion, and the alloywill remain perfectly malleable; and this, withor without other fmaller .additions, forms theordinary pewter, fuch as is ufed for meafuresfor liquor, and many fmaller purpofes, and inother countries of Europe , for many other do-meftic ufes. As lead is by much the cheapeilof the two metals, it is the intereft of the ma-nufacturer to employ it in as large a proportionas poffible, but as much danger to health maybe apprehended from this noxious metal, thisfubjeift was examined particularly by a commif-fion from the French government of fome veryable chemifts. Thefe gentlemen found, thatwhen wine or vinegar is allowed to (land inveffeis compofed of an alloy of lead and tin indifferent proportions, the tin is firft diffolved,that the lead is not fenfibly oxydated by thefeliq-v.vfs, except at the line of contact of the air
* leenhardi
and the liquor, and that no fenfihle quantityof lead is difiolved even by vinegar after Hand-ing for fome days in veflels that contained nomore than about 18 per cent, of lead. There-fore as no noxious effedf is produced by thevery minute quantity of tin which is difiolved,a pewter may be confidered as perfectly fafewhich contains about 80 or 82 per cent, of tin;and where the veflels are employed merely formeafures, a much lefs proportion of tin mav beallowed. But the common pewter of Paris wasfound to contain no more than about 25 or 30per cent, of tin, and the remainder was lead.The ipecific gravity of a mixture of tin and leadis lefs than the mean fpecific gravity of thefame proportion of the two metals feparately,confequently the bulk of the alloy is greaterthan the bulks of the metals before union, whichis the contrary to what happens in moll otheralloys. This alloy when in equal parts formsalfo the common plumbers’ folder. Whenmelted it oxydates at its furface with great ra-pidity, much more than even either of themetals feparately, and this oxyd is the bafis ofthe fineft Enamel White.
The ufes of tin are confiderable. It is em-ployed for many purpofes in fine leaf about thethicknefs of writing paper, when it is calledTin-foil. This is made from the very fineft tinwhich is firft call into an ingot, then laminatedto a moderate extent, and afterwards beat outwith a hammer, with very great manual labourand Ikill till it is brought to the requifite thick-nels, and extended perfectly uniformly withoutany flaw or break. The other ufes of tin are,very largely, for tinning iron and copper, inpewter, folder, and other alloys; and the faltsof this metal ane employed in dyeing.
TINNING of Iron and Copper. See Iron and 'Fin.
’I INC PURE. A tinfture is commonly un-derftood to be a coloured infufion of any jub-ilance in alcohol. It is a preparation much em-ployed in pharmacy with many of the articlesof the materia medica, particularly vegetablebarks, aromatics of all kind, and many of therefins and gum-refins, which yield to alcohol byinfufion that part of their fubltance in whichmoll of the medicinal virtue relides.
TITANIUM.
This is^a metal of a copper red colour,very difficult of fufion, foluble in muriatic acid,Woruu-uch,