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to the reader, A quantity of concentrated fodawas heated to rednefs in a filver crucible where-l>y all the water of cryftallization was expelled,and it was then diffolved in fuch a quantity ofwater that 367 grs. of the folution contained50.05 of the dry alkali. This quantity wasthen faturated with 147 grs. of nitric acid of1.2754 fp. gr. and which contained 45.7 percent, or 66.7 of the ftandard acid of 1-5543 fp-gr. The carbonic acid loft by the folution was14 grs. fo that the quantity of foda alone in itwas 50.05—14, or 36.05 g rs - The folutionwas then lowered by water to 1.0401 fp. fgr.-which was found by a feparate experiment to bethe degree of denfity of water containing tvttttof its weight of dry nitrated foda. The firftfolution weighed 1439 grs. and hence it multhave contained t!-.Ht= 85.I4.2 grs. of nitratedfoda. The quantity of foda employed was36.05 grs. and the quantity of ftandard acidwas 66.7 and the fum of thefe is 102.75. Butof this quantity only 85.142 entered into thecombination of the fait and therefore the diffe-rence between 85.142 and 102.75,-or 17.608,muft have been the mere watery part containedin the 66.7 grs. of the ftandard acid. Thereforeico of the ftandard acid contain 26.38 of waterand 73.62 of real acid or fuch as exifts in com-bination in dry nitrat of foda: and 100 parts ofthis fait contain 42.35 of alkali and 57.65 ofreal acid, which is equivalent to- 78.33 of theftandard.

In thefe experiments on nitric acid it becomesa queftion to determine how far changes oftemperature affect the fpecific gravity. Mr.Kirwan found that the ftrongeft acid was themoft expanded by heat and contracted by cold.From the refult of many experiments he findsthat on an average the variation of fpecificgravity for every fingle degree between 6o° and70° in an acid whole denfity -at 6o° is from1.3 to 1.4 is .0005 and for the variation between44 0 and 6o° is .0004. An acid, -of H263 fp.gr. at 6o° gains lofes for every degree between6o° and 7c 0 .00043, and for every degree, be-tween 60 and 45 0 the variation is .00036,

The affinities of nitric acid for the alkaliesand earths are in the following order, barytes,potafh, foda, ftrontian, lime, magnefia, ammo-ma, glycine, alumine, zircon.

The combinations of the nitric acid with alka-line earthy and metallic bafes, are called Nitrats ,be defcribecl in their proper place.

ihe fame theory that fuppofed the fuperiordegree of oxygenation of the pale nitric overtk coloured nitrous acid, has given the term

nitrites to the falts of the latter acid. But thisis founded on an erroneous idea of the diffe-rence between the two acids, and of the wholeimagined genus of nitrites, the nitrite of potafhalone has been ever produced, and this not bythe direct combination of the nitrous acid andpotalh but by the partial decompofition ofcommon nitre. Its properties will be mention-ed under the article nitrite.

NITRQ-MURIATIC ACID. Aqua Regia .Konigivajfcr. Germ.

The term nitro-muriatic acid Is not meant todefignate any particular acid cr modification of,acid but fimply a mixture of nitric or nitrousand muriatic acid, or fometimes muriat ofammonia, which when united produce a veryimportant agent in many chemical operations.It is particularly as a folvent for gold that thiscombination (which is very ancient) has beenknown, and hence it was termed by the al-chemifts aqua regia, (gold being with them theking of metals) and is nearly the only fubftancethat can diffolve this noble metal. The com-pofition of the aqua regia fitted to diffolve goldhas been deferibed under that metal. Katinaalfo, like gold, is infoluble in either of thefeacids fmgly, but yields to a mixture of the two,but in different proportions. Antimony alfo isfcarcely foluble in any acid but the uitro-muria-tic, and the compofitian of the mixture the beftfitted for this purpofe is ftill different from dieothers.

Berthollet in his excellent and profound effayon chemical ftatics has fome good obfervationson this acid. When pale nitric and muriaticacid are mixed, an effervefcence quickly takesplace, the liquid becomes of a high amber-redcolour, and a very pungent vapour is extricated,obvioufly fnielling very different from the va-pour of the nitrous or muriatic acid fingly, butclofely refembling the oxymuriatic acid gas,which is the adiual vapour given off. This isformed by a partial decompofition of a portion ofnitric acid which furrenders part of its oxygen tothe muriatic acid gas, whilft the remainder isnitrous gas, wliich diflolving in the acid givesthe high colour, and may be driven off byfaturating the acid with an alkali or earth.The above decompofition of nitrous acid, andevolution of oxymuriatic acid ceafes when themixed acid is faturated with the nitrous gas, andhence the fuming nitrous acid which alreadycontains much nitrous gas, gives lefs oxymu-riatic vapour than the pale acid. If nitrous gasbe mixed with oxymuriatic acid gas over mer-cury or over very little water, the nitrous gaa