TIN

TIN

( 424 )

•fuppofed, but a fub-muriat , pvecifely the fameas the fait produced by adding much waterto the cryftallized murlat. The fupernatantliquor is fill acidulous, fo that the iirft effedtof the alkali is not to faturate the wholeexcefs of acid, but to abffact the greaterpart of :he acid from that portion only of themuriat which is precipitated as a fub-muriat.This adtion of ihe alkali continues to the laft, fothat as long as a particle of muriat of tin remainsin folution, it remains acidulous. If the ad-dition of potalh is continued after all the metalis precipitated from the folution as a fub-muriat,(no artificial heat being ufed) this precipitate•gradually difappears, and a triple combinationof muriatic acid, potafh, and fub-oxyd of tin,is formed, which is partly cryltaliizable inrhomboidal prifms. The triple fait, producedin a fimilar manner, by ammonia and by barytes,aiTumes the fame form; when by l'oda or ltron-tian, the form is that of line needles; themuriat of tin and lime is deliqueiccnt. If,however, the precipitated fub-muriat is digeltedwith an alkali, and beat applied, the acid is to-tally feparated from the oxyd, and the latter iseither re-dilfolved in the alkali, or, if but littlealkali be ufed, moll of it remains at the bottomin the form of a pure grey fub-oxyd, in whichthe proportion of oxygen is only about 22 percent, whereas the fuper-oxyd formed by nitricacid and tin, and deprived of its fmall retent ofacid in the fame way, contains about 28 percent, of oxygen.

'The carhonats of potafh and foda precipitatethe folution of muriat of tin with a Srifk effer-vefcence. The precipitate is not however acarbonat of tin, but a fub-muriat, as with thepure alkalies, and an excefs of the carbonat inthe fame manner, re-diffolves the precipitate.

Another change, however, takes place, when■the alkalies are digelted with the oxyds of tin.The alkalies diffolve both thefe oxyds, but theiraffinity with the fuper-oxyd is much greater-than with the fub-oxyd whence it happens,that if a clear folution of the fub-oxyd in caulticpotafh be kept in a perfectly doled veffel, atthe end of ten or twelve days a lingular eauli-flower-fhaped depofit is formed, which Proullccnfidcrs as veguline tin, but which appearsrather to be tin in an extremely low liate ofoxydation, as it is foluble in cold muriatic acid,without giving out hydrogen. 1 The fuper-natant alkaline liquor, on the other hand, nowcontains the metal in the highelt ftate of oxyda-•*40115 for when feparated from the alkali by

muriatic acid, and re-dilfolved in the famemenifruum, it gives no precipitate whatever tothe folution of corrofive mercurial muriat, whichis a tell of the l’uper-oxydated folutions.

In this cafe an unequal divifion both of themetal and oxygen takes place; one part of themetal, ino which the greater part (if not all)of the oxygen is condenfed, forms a permanentunion with the alkali, and the remainder of themetal falls down nearly in the reguiine hate,and fymmetricaliy arranged. 1 his changetakes place more fpeedily, by boiling a feiutionof potalh on a greater quantity of the oxyd pre-cipitated from a muriat than it is capable oi dif-folving.

We proceed to the Super-oxydated Muriat.This fait was long partially known, before itstrue nature was explained, as it conlfitutes,when concentrated by diltillation, that lingularfmoking compound firft difeovered byLibavius,which on that account was termed Smoking Liquorof Libavius. It is prepared in the following way:melt, in an iron ladle, 5 oz. of pure tin, add toit 5 drams of mercury, Itir them together, andpour out the amalgam into a marble mortar,into which put 20 oz. of corrofive mercurialmuriat in line powder, and mix the wholethoroughly. Put the whole of the mixture intoa glafs retort, with a receiver, not quite clofelyluted, and apply a moderate heat, with anArgand lamp or a fand bath. At firft, about5 oz. of a colourlels liquid diltills over quietly,alter which there rifes, quite fuddenly and witha moderate explofion, a great quantity of whiteheavy vapour, which condenfes into a tranfpa-rent liquid, and mixes with that which has firltpuffed. This is to be quickly poured into awell-ltoppered glafs phial, and is the SmokingMuriat of Tin, or Liquor of Libavius. The ufe ofthe mercury, in amalgamating the tin, is merelyfor the convenience of dividing it, as the filingsof tin alone, with the corrofive muriat, willaufwer the fame purpofe.

Preuft gives, as the beft proportions, 8 oz.of powder of tin, i^probalvy luch as is made bymelting the metal, and {halting it in a box) and24 oz. of corrofive fublimate, which affords 9oz. of the fir.oking liquor.

If the receiver be changed after the fri.o. ingliquor has come over, and the heat be very muchincreafed, a folid butter of tin firft iublimes,which appears to be the muriated fub-oxyd,mixed with globules of mercury, when theamalgam has been originally employed. To-gether with this muriat there rifes a quantity

1 .Berthoilei