T I N

T I N

C 427 )

The ftate of oxydation of the metal in this fo-liation muff vary, but when it is recent, and hasbeen made very gradually, and without heat,the tin mult be in low oxydation, which is theftate probably the moll defirabie for the dyer,as the acid is more faturated and lefs liable todepofit oxyd by keeping.

When tin filings are thrown into oxymuri-atic gas they take fire and burn with a bluifh-white flame. The refidue is partly foluble inwater.

The liquid oxymuriatic acid diflolves thismetal quietly without effervefcence. The re-fill t is a muriat of tin more or lefs oxydatedaccording to the quantity of acid employed.

Moll of the vegetable acids a£l upon tin.

Vinegar, either common or diitilled, whendigefted with tin filings, particularly with theaffiftance of heat, aflumes a whitilh opalefcentcolour, a difagreeable fmell and metallic tafte,gives a yellowifh white precipitate with hydro-fulphuret of potafh, and a deep purple precipitatewith nitro-muriat of gold. It therefore holdsthe tin which it has diflolved, in a low ftate ofoxydation. This folution readily depofits mollof its metallic contents as an infoluble oxyd,when by expofure to air it has abforbed anadditional quantity of oxygen. If the recentfolution is flowly evaporated till it begins toffiewafahne cruft, and is then fuffered to remainundillurbed in a cool place for a day or two, itdepofits groups of needle-formed cryftals ofacetite of tin.

The acetic acid, being more concentratedthan common vinegar, diflolves tin more readilyand in fomewhat larger quantity, but even withthis acid the quantity diflolved is very fmall.

The fub-oxyd of tin produced by faturatingthe common muriat by a carbonated alkali, alfodiflolves in vinegar, but the perfedl oxyd isinfoluble in this as in moft other acids.

Carbonated water added to a folution of ace-tited tin caufes a white powder to precipitate,which is probably a carbonated fub-oxyd.

, A very concentrated acetite of tin is made pby adding a faturated folution of cryftallizedmuriat of tin to acetited lead. A double de-compofition takes place, muriat of lead is pre-cipitated, and the fupernatant liquor is chieflya flrong acetite of tin. This is flrongly re-commended by the inventor as a mordant for avariety of dyeing procefl'es.

Tin is foluble in the acid of tartar, and thisfolution is of importance in manufacture, as itis the method by which -wet tinning is per-i HaufTman.

formed on copper and brafs. Pins are whitenedin this manner, but by a compound menftruum.

This procefs is eafily performed: a folutionof about one part of cream of tartar, two partsof alum, and as much common fait, is made ina moderate quantity of water, and tin filings orgranulated tin is thrown in, and the liquorboiled. The pins, which are made of braiswire and perfectly bright, are then put in, andafter remaining in the boiling liquor for a time,they are compleatly covered with a beautifulwhite uniform coating of tin, which is the ftatein which they arc ufed. .

It is not neceflary to employ this mixture offalts for the mere tinning of copper or brais.Either of thefe three falts fingly with tin filingswill anfwer the purpofe, but cream of tartargives a duller and more leaden-looking tinning,and alum on the other -hand gives a veryfine filver white but without glofs, fo that themixture above-mentioned is found to producethe moft defirabie hue.

In a chemical point of view this operation iscurious, and appears to prefent a contradictionto the ufual laws of affinity, for when tin isimmerfed in a common folution of copper, itprecipitates moft of the copper in the metallicftate.

The circumftances requifite to produce aprecipitate of metallic tin on copper, have beenexamined in an able fet of experiments by Prof.Gadolin, a Swedifli chemift, an account ofwhich is inferted in the Stockholm Tranfaelionsfor 1788, to which are added fome other expe-riments and remarks by Baron de Gedda. q Itis to he obferved, that the circumftances relat-ing to the oxygenation of metals in their foiu-tions in acids were very incompleatly known atthat time, fo that we may now account forphenomena which mull have been inexplicableat that period. The fadts however cannot vary,and are always valuable. This chemift chiefly-confined himfelf to the adlion of a Angle fait,namely tartar, or its acid. We ftiall feledl andgive in a few words fome of the experiments.

1. Tartrite of potaffi was added to nitro-muriat of tin, which caufed a white precipitate oftartrite of tin, which was edulcorated ami dried.Some of this precipitate was boiled with water,and copper was immerfed, but the copper wasin no degree altered.

2. Some of the above tartrite of tin wasacidulated with tartareous acid and copperwas boiled in it, but with no effedt.

q. Some of the fame tartrite of tin was treated

’ Journ. de I’hyf. tom. 34, p. 361 & 43 °-

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