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©n a platina dish, and a small' vessel full of drymuriat of lime previously weighed was placedin the tubulure of the vessel. The receiverwas first filled with mercury, which was re-placed by oxygen gas extracted from oxymuriatof potash, and another small glass vessel wasadopted, in which a portion of the gas could bewithdrawn for examination.

The analysis of the gas was performed in thefollowing way. The; oxygen was extracted byhydrosulphuret of potash saturated with azoticgas, which was allowed five days for its opera-tion without agitation, and with care to pre-serve a nearly uniform temperature, that noportion of the azote contained in the eudiome-tric liquor should be expelled. This method heobserves is more exact than Volta’s, of detonatingthe oxygen with hydrogen, when the only im-purity mixed with the oxygen is azotic gas ; butVolta’s is preferable where any carburettcdhydrogen is present, as the sulphuretted liquorabsorbs a sensible portion of this latter gas.

To separate the carbonic acid gas, the authorprefers a small bulk of a very concentrated.solu-tion of caustic potash ; for he finds by direct ex-periment that lime-water, or rather the wateralone, absorbs a little oxygen by agitation aswell as all the carbonic acid gas, when no greatproportion of azote is present. Thereforethough lime-water will accurately separate thecarbonic acid alone from a mixture of this gaswith common air, it cannot be depended on togive such exact results with a mixture of car-bonic acid and oxygen. Messrs. Allen andFepys had ascertained the accuracy of lime-water in the former case, but not in the latter.

The author further observes, that when anysubstance containing hydrogen, such as wood,oil, &c. is burnt in oxygen gas, a small quantityof the hydrogen escapes combustion, howevergreat the excess of the oxygen is, and even cannotbe ignited in this excess of oxygen by the electricspark. The only way of detecting and estima-ting this hydrogen, is to addjJOO additionalmeasures of hydrogen to 200 of the impureoxygen to be examined, which are then in theproportions capable of detonation; and then toobserve whether the condensation is greaterthan would be produced by pure hydrogen andoxygen, allowing 200 measures of the formerto condense 100 of the latter. M.Saussureasserts that every kind of hydrogen, even thatobtained by the electrization of pure water,contains a small portion of carbon, so as to fur-nish a sensible quantity of carbonic acid whenburnt with the purest oxygen which has pre-

viously been agitated with potash. This car-bonic acid he finds to be about 3 measures from1000 of hydrogen and 1000. of oxygen, but itis only made sensible when an excess of oxygen'is employed; for when, on the contrary, amexcess of hydrogen is used, scarcely any indica-tions of carbonic acid are given, but the authorasserts that then the unconsumed hydrogen istO'a certain degree oxy-carburetted.

When a mixture of oxygen and azote is ex-posed to the electric spark with hydrogen inVolta’s eudiometer, a sensible quantity of theazote is condensed, which in a single detonationmay amount to 2 percent, of the azote present.When much oxygen remains after the combus-tion, the condensed azote furnishes nitric ornitrous acid; but when the hydrogen is in ex-cess, the azote produces nitr.it of ammonia.This same ammoniacal salt is always generatedby the slow combustion of hydrogen and of oxy-carburetted hydrogen in the open air.

The carbonaceous substances burnt in theseexperiments were plumbago, anthracite, charcoalarising from the decomposition of oii of rose-mary, box-wood charcoal, and the charcoalwhich remains after passing the vapour of sulphurthrough it in the preparation of carburettcd sul-phur. Themodeof performing these experimentswas considerably complicated, as may be inferred,from the preliminary eudiometrical remarks.

We shall select the experiment on the com-bustion of plumbago: 0.588 grammes of Cor-nish plumbago dried at a red-heat was burnedin the receiver full of oxygen gas for an hour'by the sun’s rays collected through a lens.There remained 0.33 grammes of red oxyd ofiron, the oxygen of which was .0099, and theiron therefore was .0231, and hence the carbonconsumed was 0.588—0.0231 “0.5019. The*gas before combustion, reduced to the standard:pressure and temperature, was I75S.8 cubiccentimetres, and after combustion 1.750.4, giv-ing a diminution of 8.4. The vessel of muriatof lime enclosed in the receiver had increasedin weight 5 centigrammes, on? of which isto be reckoned as the moisture absorbed from-the air during the shoit time of its introduc-tion into the vessel before the experiment, so.!that the moisture absorbed from the gas alonewas 4 centigrammes, which is within of .the quantity of moisture contained in the un—dried oxygen at the temperature employed..Hence it appeared that no water was produced*by the combustion of the plumbago._

The oxygen examined befbre combustion, bythe test, of hydrosulphuret. of potash, shewed: