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thing is diflolved. Then put all the folutionstogether, and drop in the tefted fulphuric acidfrom a vial containing a known weight of thefame, till the flighted poffible excefs of acid isindicated by a paper tinged with litmus. Afterthis, heat the mixture to expel all the carbonicacid, and if the liquor changes turmeric paperadd a few drops more of fulphuric acid till itceafes to fhow an excefs of alkali. Now weighthe vial of fulphuric acid, and thus afcertainhow much has been expended in faturating thealkali, and for every loo parts of real acid (asprevioufly determined by muriat of barytes) thusemployed, fet down 121.2 of pure potafh. Thealkali being the part which gives value to thewhole, this is all the examination which in or-dinary cafes is required, but if the analyfis is tobe carried further—

3d. Take 500 grains more of the alkali, dif-folve it in boiling water and pour the folutioninto a flalk; then place the flaik and a vial con-taining from two to three ounces of pure nitricacid into one fcale of an accurate balance andequipoife them. Afterwards add the acid bydegrees to the alkali as long as any effervef-cence takes place, and the lofs of weight indi-cates the amount of carbonic acid. The folutionwill now probably cryftallize, a fufficient quan-tity of water is therefore to be added in orderto diflolve the cryftals, and nitrat of barytes isto be dropped in fo long as any precipitatetakes place, xoo parts of the dried fulphat ofbarytes thus procured indicate 73.6 of fulphatedpotafh. This being removed, add to the clearliquor nitrat of filver till it ceafes to be decom-pofed. 100 parts of muriated filver fhow 41.34of muriated potafh. Thus the faline contentsare all of them afcertained, viz. potafh, carbonicacid, fulphat and muriat of potafh. The earthypart is fhown in the infoluble refidue, No. 2,and in the precipitate which falls down onboiling the alkaline liquor after its faturationwith fulphuric acid. If any fulphur is containedin the alkali, as is the cafe with the black pot-afh, this will fall down together with the earthupon faturation with fulphuric acid, and is fepa-rated from the earth by a red heat.

Having now treated of the impure fubcar-bonats of potafh we fhall conclude this articlewith an account of the purer fubcarbonats andthe perfect carbonat of potafh.

The molt important of the purer fubcarbonatsis fait of tartar , which is prepared in the winecountries in confiderable quantity, and is thekind generally ufed in medicine. The lees ofwine and the tartar that is depofited on the Tides

of the cafks are put into fmall bags about a footlong, and fubjedted to a itrong preffure in orderto fqueeze out all the wine which is difpofed ofto the brandy diflillers ; the contents of the bagsbeing carefully taken out, without breaking, formmafifes like loaves, which are dried in the fun,and then piled up in a furnace with alternateftrata of charcoal. The fire being kindled, andthe draft properly regulated, the acid and in-flammable matter of the tartar is burned offwithout fufing the alkaline part; when the pro-cefs therefore is finifhed, the loaves remain ofnearly the fame fize as before, but very porousand perfectly white. Being then broken intopieces they are diflolved in hot water, and theclear lixivium being evaporated to drynefs andthen flightly calcined is fit for fale. parts oftartar yield one of fait of tartar.

A more expeditious but lefs economical wayof procuring fait of tartar is to mix equal partsof crude tartar and nitre, and project the mix-ture into a red hot crucible. A rapid deflagra-tion takes place, the nitric acid, and the com-buftible parts of the tartar mutually decompofeeach other, and there remains behind the alka-line bafe of each united with fome carbonicacid. This preparation is called white flux,nitre fixed, by tartar , extemporaneous potajh.

The perfectly faturated carbonat of potafh hasnot been known to chemifts longer than thetime of Bergman. It may be prepared in twoways: the firft, which was difcovered by Ber-thollet, is as follows. Take equal parts of faitof tartar and carbonat of ammonia, diflolve thewhole in warm water, then pour the folutioninto a retort, and proceed to flow diftillation;the potafh having a ftronger affinity for carbonicacid than ammonia has, deprives this latter ofits acid, and in confequence ammoniacal vapouris given out in great quantity: when this ceafes,the contents of the retort are to be poured intoa convenient veflel, where, by refrigeration, acopious depofition of cryftallized carbonat ofpotafh will take place.

The other method, and that which is gene-rally pradtifed, is to put a folution of fait of tar-tar into an apparatus for impregnating waterwith carbonic acid, and then to throw in thisacid till the alkali is quite faturated, and refufesto take up any more; on opening the barrel, itwill be found lined with large cryftals of carbo-nated potafh.

The form of its cryftals is that of a tetrahe-dral rhomboid with dihedral fummits. Itrequires for its folution about 4 parts by weightof cold water, but diflolves in of its weight