MUR

MUR

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It was Scheele a who firft difcovered in con- by offering a fupport on which it may concretetraditlion to the eftabiifhed lav/s of chemical and efcape the re-attion of the muriated lime,affinity, that muriat of foda might be decom- this method is indeed connderabiy ieis expedi-pofed by means either of iron or quick-lime in tious than that difcovered by Scheele, yet itan atmofphere confiderably charged with car- feems to be the very mode employed by Naturebonic acid. Thu£ if a plate of iron is dipped at the Natron lakes of Egypt, as Berthollet hasin a faturated folution of common fait, and then fhewn in a very interefting report on thisfubjcft.'hung up in a cellar, a decompofition of the fait Qf the threp modes of decompofing muriat ofwill be found to have taken place in the courfe foda mentioned above, that by means of quick-of a few days ; the furface of the iron will be lime is the only one tnat has been attempted on aftudded with drops of a yellow liquor, confilting large fcale, but though fuperintended by io ablefor the moil part of muriat of iron, while the a chemift as iviorveau' 1 it does not appear tofoda liberated from the muriatic and combined have been attended with fuihcient advantage towith the carbonic acid, will have affirmed the ap- counterbalance the expence .ol time and fuel.'pearanceof fmall fpicular cryftals rifmg from the The procefs employed differed in no refpeflfurface of thofe parts of the plate that are not from that of Scheele, except that the mixtureoccupied by the muriated iron. So in like after it had ccafed to yield any more foda wasmanner if quick-lime be formed into a pafte re-calcined and again treated with a folution ofwith a ftrong brine of common fait, and the common fait. It has been propofed as an im-mixture be placed in a cellar for fome days, provement of this procefs, to mix with the limethe furface of the lime will be covered with a and fait a fuihcient quantity of clean fand tolight down of ilender cryftals of carbonated convert it into mot tar, and then to line cellarsfoda; thefe being removed they will be fuc- or other excavations with it, in order to expofeceeded by a fecond fimilar efflorefcence, and a larger furface to the aftion oi the air. I herethe fecond by a third. The decompofition in is no doubt that the yield of carbonated fodaboth thefe cafes is attributed by Scheele, and would thus be greatly augmented, and it is notapparently with great reafon, to the efflorefeent improbable where natural or artificial excava-quality of carbonat of foda, which readily dif- lions could be conveniently obtained, that thepofes it to rife from the furface where it is increafed produft would more than equal thegenerated in fpicular cryftals, and thus feparate additional expence.

itfelf from the muriat of iron or lime by which The polftbility of decompofing common faitit would be again decompofed. This explana- by means of litharge or any other of the oxydstion of the fadf derives additional force from the of lead, was firft afeertained by Mr. Turner,circumftance that muriat of potafh is not decom- who obtained a patent for the difeovery in thepofable either by lime or iron, probably becaufe year 1780. His procefs is the following: 6carbonat of potafh, nor being an efflorefeent fait, To ten parts of any of the oxyds of lead add fiveis unable to feparate itlelf from the reft of the parts of muriated foda, previoufly diflblved inmafs. Vauquelin b feems difpofed to attribute water; grind the whole together till the lithargethe decompofition of common fait by lime, to becomes almoft impalpable, and then let thethe formation of an infoluble muriat of lime mixture Hand for twenty-four hours, in whichwith excefs of bafe, but this appears to be dif- time the lead will appear of a white colour:proved by an obfervation of Scheele, that if the . the mafs, which will have acquired a tolerablyrefiduum after the efflorefeent fait has been col- folid confidence, muft now be broken down inIedted be lixiviated, and the excefs of lime in water and be well wafhed ; the liquor will con-the folution be got rid of by means of carbonic tain the alkali of the fait, and the white infolubleacid, the remaining clear liquor will furnifti an refidue confilts of the litharge combined withabundant precipitate of carbonated lime on the muriatic acid. This refidue after being care-addition of the effiorefeed carbonat of foda, fully lixiviated and dried, if expofed on a mufflethus (hewing that the folution contains muriat or in any other fuitable way to a calcining heat,°t hme in its ordinary (fate. Berthollet has acquires a yellow colour, varying in tint accord-lnewn that even carbonat of lime, when in ing to the temperature ; this yellow muriat when^f S , exce ^ s ’ ' s capable of decompofing muriat ground up with oil and varnifh in the ufualol . lo da, more efpecially if draws or any other manner, forms a pigment known by the namefimilar fubftances are ftuck upright into the oi patent yellow, and very extenfively employed,mats, to alfift the efflorefeent power of the foda, in coach-painting.

(iflays, p. jj. Ann. Chem. xxxi. p 10. «,Mem. de l’lnftit. de Cairo. 4 Ann.Chim. xix p. 102,

e Repertory xii. p. 13 7.