MUR

M U R

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thofe of Mr. W. Henry, e the principal refultsof which we Avail proceed to detail. Whenmuviatic acid gas confined in a glafs jar overmercury is fubje£led repeatedly to the electricihock, it undergoes a diminution of bulk, awhite matter appears on the infide of the tube,and upon fubfequent mixture with water a por-tion of gas remains unabforbed, and appears tobe hydrogen in a ftate of confiderable purity.The diminution of the acid gas and all the otheraccompanying phenomena are the moft remark-able when the acid operated upon is that whichis firft difengaged on mixture of fuiphuric acidand common fait: the part that comes overduring the latter end of the procefs is confider-abiy lei's a(Fe£led by the eleftric fliock than thatwhich is firft prod.uced; and if the gas hasbeen previously dried for fome days by contadhwith folid muriat of lime, the diminution ofbulk by electrization is fcarcely perceptible.The white matter that appears during the pro-cefs is mild muriat of mercury or calomel :hence if is obvious that in theie experimentsoxygen and hydrogen are difengaged, of whichthe "oxygen together with part of the muriaticacid unites with a portion of the mercury, whilethe hydrogen and the refidue of the acid remainin the ftate of gas. Now as the componentpa ts of water are oxygen and hydrogen, and asthe amount of thefe l'ubltances difengaged bythe eleCtric fhock is in an inverie proportion tothe drynefs of the gas, it is reafonable to con-clude that the hydrogen and oxygen proceedfrom the decompofition of water and not ofmuriatic acid. This conclufion is furtherftrengthened by another fa£t, namely, that aftera number of fliocks have palled through thegas its diminution ceafes, and if it is then trans-ferred to a frelh tube over mercury and againfubjeCted to the action of ele&ricity, no furtherchange in bulk is experienced, nor is there anyformation of calomel; but if the acid werereally decompofed, the production of calomelought to continue as long as any acid gas re-mained. Again, when muriatic acid gas iseleCtrified in a glafs tube without the contaCtof mercury, the refult is found to be oxyrnuriaticacid gas mixed with hydrogen. Several attemptswere made by Mr. H. to deoxygenate muriaticacid gas by mixing it with carburetted hydrogenand eleCtrifying it, but without fuccefs : themixed gaffes were indeed expanded and carbonicacid was produced, but thefe changes were ob-vioully caufed merely by the decompofition ofthe water, fince after they had entirely ceafed a

little water was introduced, and the quantity ofmuriatic acid abforbed was equal to what wouldhave been taken up if the acid gas had beenelectrified by itfelf.

So various and uniformly ineffectual havebeen the attempts to decompofe this acid, thatwe muff conclude either that it is a firnple body,or if, like many other of the acids, it be con-fidered as a compound of a combuftible bafewith oxygen, the affinity between the two muffbe regarded as more powerful than that of anyof the known combuftible bodies with oxygen.

The affinities of muriatic acid are arrangedin the nioft recent tables in the following order.Barytes, potalh, foda, ftrontian, lime, ammonia,magnefia, glycine, alumine, zircon, metallic'oxyds. This order however is not correCt, forthe oxyds of filver, mercury, lead, and probablyantimony, are capable of decompofing mod ifnot all the neutral and earthy muriats.

The ufe of muriatic acid in the laboratory isvery confiderable, but in medicine and the artsit is but little employed except in the form ofmuriat or combined with fome falifiable bafe.It is worth remembering by the chemift thatnothing takes off the cruft of oxyd of iron,which in many experiments is found adheringwith remarkable cloienefs to glafs veffels, fofafely and quickly as a little warm dilute muri-atic acid.

Muriat of Potash, or Sa.'t of Sylvius.

Muriat of potafh is rarely if ever foundnative except in the afhes of a few plants andin fome animal fluids, efpecially milk. To ob-tain it pure it muft be formed either by the dire£tunion of muriatic acid and potafh, or its carbo-nat, or by decompofing common fait by potafh.The former is the belt method for a chemicalinveftigation of its properties.

If a faturated folution of this fait is flowlyevaporated the muriat of potafh feparates in theform of regular cubes, which have a fait andbitter tafte, together with a degree of pungencylike muriat of ammonia. It diffolves in threetime-s its weight of cold water, and by boilingfomewhat more is taken up, and hence a clearhot faturated folution deposits a portion of faitby cooling, in which refpeCl it differs from puremuriat of foda. Muriat of potafh when brifklyheated fharply decrepitates, but does not liquefyin its water of cryftallization, this being only about8per cent, which flies oft at a heat below ignition..At a full red heat the fait melts, and if the heatis further urged' the fait itfelf flies off in a

* Phil. Tranf. for i-Soo, p. 188,