FLU

( 107 ) FLU

fumes, but it mixes uniformly with dry air, andhence it is an excellent test of hygrometricmoisture. It has no action whatever en glass.It corrodes vegetable and animal matters aspowerfully as the strongest sulphuric acid, andcarbonizes them, so that it instantly blackenspaper.

It converts alcohol into ether. It does nothowever corrode the skin whilst experimentsare made upon it. Water appears to dissolve atleast as much of this gas as of muriatic acid gas,and at the same time the water heats and expandsmuch.

When it is saturated it forms a limpid fumingcaustic liquid, which when heated will give outonly a fifth of the gas that it had absorbed, andit then resembles strong sulphuric acid in causti-city and in appearance, and like this acid itsboiling point is very high, and when distilled byitself, it condenses in long streaks on the re-ceiver.

The fluoboracic acid combines very easilywith the various salifiable bases. When satu-rated with ammonia and when the solution isevaporated to dryness, a higher heat expels awhite sublimate of fluatof ammonia mixed withsome borate of ammonia, and pure fused boracica.cid remains behind.

These chemists did not pursue the examina-tion of these compounds much further, exceptto ascertain that the fluoboracic gas is not alteredby passing through red-hot iron turnings.

Mr. J. Davy (in the paper above quoted) findsthat this compound acid gas may be procured inan easier manner than that just described. Itis sufficient to heat gently in a common glassretort, one part by weight of fused boracic acidmixed with 2 parts of iluor spar, both in finepowder, and about 1.2of sulphuric acid. Com-mon calcined borax will even answer, but not sowell. If the heat is gentle the retort will beuntouched, and pure fluoboracic gas will beproduced. If the heat be raised higher, aviscid mixture of sulphuric and fluoboracic acidcomes over. Not more sulphuric acid shouldbe used than is necessary to decompose thefluor spar, on account or the quantity of thefluoboracic gas which is absorbed by the sulphu-ric acid. The specific gravity of this gas, Mr.J. Davy estimates to be to that of common air,as 14.7 to 6.2, and hence 100 cubic inchesweigh 73.5 grains. Water condenses no lessthan TOO times its volume of this gas, which ismore than of any other known gas Water thusfully saturated has 1.77 specific gravity. Sul-phuric acid condenses about 50 times its volume

of the gas, and forms a dense tenacious com-pound.

Some singular results take place on com-bining the fluoboracic gas with ammoniacal gas.When equal volumes of the two gasses are used,they condense into a solid white opake salt.When a double or triple quantity of ammoniais employed, the dry salt resolves itself into atransparent colourless fluid, though without con-taining any water.

Decomposition of Fluoboracic and SilicaledFluoric Gas.

The singular energy of potassium in deprivingmost oxyds of their oxygen, and leaving theirbases separate, has been employed to discoverthe hitherto unknown radical of fluoric acid.But here a particular difficulty occurs, as nomeans have yet been found of obtaining fluoricacid free from water, except by combining itwith silex or with boracic acid in the form ofgas. As the presence of water entirely de-feats the purpose of applying potassium, it isnecessary to take the other alternative ofemploying one of the two compound fluoricgasses.

Messrs. Gay Lussae and Thenard have ex-amined the effect of potassium on both thesegasses.

Potassium is not serisibly acted on by drysilieated fluoric gas at a common temperature,but if it is melted in the gas by a gentle heat, itthickens and burns strongly with much light andheat. In this process a large quantity of thegas is absorbed, very little hydrogen is givenout, and the potassium is converted into a red-dish brown substance. When this latter sub-stance is digested with hot water, some hydro-gen is given out, the hot water holds in solutionsome fiuat of potash; and the insoluble portion,after calcination in an open crucible or combus-tion in oxygen, yields a triple fluat of potash andsilex. From these facts the authors conclude,that the potassium when burned in silieatedfluoric gas, decomposes the fluoric acid, andthat the reddish brown substance is a compoundof fluoric radical, potash, and silex, and perhapssome undecomposed fluoric acid, and hencewhen it is afterwards digested with water, thefluoric radical returns to the state of fluoric acid,and forms with the potash and silex an insolu-ble fluat of silex and potash. Potassium burnswith great ease in this gas, and when only asmall quantity is used, it may be done in a smallglass tube full of the gas, into which the potas-sium is introduced on an iron support, and heatapplied externally by a spirit lamp. Sodium-