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to afcend along with them. A quantity "of air of this kind was collected at the King's

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Bath, by inverting a glass, and holding it over the bubbles as they rofe, and then conveying it into an inverted bottle, which, "when full, was carefully corked up, and "carried away. The air thus obtained an"fwered in every respect to fixible air, preci"pitating lime in lime-water, and having "every other quality which that fubftance << poffeffes."

Being informed of this, I thought it unneceffary to repeat the experiment, but finding, upon inquiry, that Dr. Nooth had not examined what proportion the refiduum of the fixed air bore to the whole, or of what quality that refiduum was, though he speaks of the whole as containing every quality that fixed air poffeffes, I thought it would not be amifs, as I was upon the spot, to make the trial myfelf. Accordingly, I took about a pint of that air, in nearly the fame manner that Dr. Nooth had done, and found, upon examination, that only about of its bulk was fixed air, precipitating lime in lime-water, and being readily abforbed by water. The reft extinguished a candle, and was fo far phlogisticated, that two measures of it, and one of nitrous air, occupied

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cupied the space of 2% of a measure; that is, it was almoft perfectly noxious.

Had I had more leifure,, and a better apparatus, the experiments might have been made with more accuracy; but I do not think that, whenever they are repeated, they will be found to be materially wide of the truth, though it is poffible that the ftate of the air in the water, and especially that which rises through the wa ter, may be subject to variation, The meafures were only estimated by the eye; but then all who were prefent agreed very nearly in the fame eftimation.

Being in Germany in the fummer of the year 1774, we happened to pafs by the famous fpring of Seltzer-water, near Schwallbach, and also another very hot spring near the road from that place to Mentz. Through both thefe fprings there was a bubbling of air, exactly fimilar to that in the Bath-waters; but I had not time, or convenience, for making the fame experiments upon them, and therefore contented myself with finding that the air of both of them extinguished a candle.

It is well known that all fermented liquors, that are not quite flat or vapid, contain fixed air; and I had the curiofity to try, what pro

portion

portion of this air is contained in different kinds of wine, and in wines in different ftates. For this purpose, I took one of the phials with a ground-stopple and tube, represented fig. e, containing of an ounce-measure, and filling it accurately with each species of wine, I plunged it into a veffel of water, which was fet on the fire to boil, receiving the air in quickfil ver. The air that I got from all kinds of fermented liquors was pure fixed air; but, except champaigne and cyder, it was in much lefs quantity than I expected; the refults being as follows.

The quantity of air contained in
of an ounce-meafure.

Madeira, was

Port of 6

years old

Hock of 5 years
Barrelled Claret

Tokay of 16 years

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Champaigne of 2 years 2
BottledCyder of 12years3

Some champaigne fparkies much in confequence of containing much air, but there is a kind of champaigne which does not sparkle, and contains very little air. The difference, as I was informed, when I made inquiry concerning it, in that part of France where the wine is made, is owing to this, that when they wish Q ?

to

to have the wine fparkle, they check the fermentation as much as poffible at the time that the wine is made; fo that the fermentation going on gradually, the fixed air produced by it is abforbed by the liquor: whereas, when they do not chufe to have it sparkle, they let it ferment freely, like any other kind of wine.

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In other cafes, therefore, where fermented liquors contain much air, as in most kinds of malt-liquor, cyder, and our English madewines, I take it for granted, that the fermentation is either purposely checked, or that the liquor is of fuch a nature, that the fermentation will neceffarily continue a long time, after it is put into the cafk or bottle.

I once found that a quantity of port-wine contained its own bulk of fixed air; but I now imagine that the wine was not genuine, but must have been made chiefly of cyder. Perhaps this may not be a bad method of diftinguishing genuine foreign wines from compofitions made of cyder.

SEC

SECTION XIII.

Mifcellaneous Obfervations.

I.

I

I have mentioned a fact, which fhews that chalk retains fixed air very obftinately; fo that neither the folar rays, nor the strongest heat of a fmith's fire, continued for a long time, can expel the whole quantity that it contains. have also found, that a fmall quantity of fixed air was contained in the beft quicklime that I could procure; fince ftrongly concentrated acids would ftill expel a fmall quantity from it. I mention this, chiefly, for the fake of an obfervation which may not be new, but which, if it be new, may be of fomeufe, viz. that when. I had heated fome pieces of quicklime in oil of vitriol, in order to extract from it all the air that I poffibly could, the next day I found the oil of vitriol folid and tranfparent, exactly refembling a thick jelly; but it became fluid again with the heat of my hand. This may, probably, be a good and expeditious method of concentrating this acid, the quicklime abforbing its water.

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