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Water at about 50° may by common meansbe made to take up nearly its own bulk of fixedair, but in the large way with a ftrong forcingpump three times as much may be thrown in.Water thus highly carbonated muft be inclofedin ftrong bottles corked with particular precau-tions, and when the cork is drawn, the liquorfroths and flies out like very brilk cyder.

Mr. W. Henry in his valuable experiments onthe abforption of gaffes by water, c has fhewnthat the quantity of carbonic acid abforbed un-der equal circumftances of temperature, preffure,and agitation, is alfo much regulated by theactual quantity of gas ufed, and by its purity,or in other words its proportion to the refidualatmofpherical air contained in the veffels and inthe water before the experiment, which no boil-ing nor expofure in an exhaufted receiver canentirely feparate. Thus, if 20 meafures of nearlypure carbonic acid gas be agitated with 1 o mea-fures of water at 55 0 , full 10 meafures of thegas (or equal in bulk to the water) are abforbed;but if the fame quantity of water at 55 0 be agi-tated with a mixture of 20 meafures of car-bonic acid, and 10 of common air, only 6 mea-fures will be taken up by the water. This isfomewhat analagous to the obfervation of Dr.Brownrigg, that in carbonated water, howeverfaturated, the gas will not efcape when inclofedin an air-tight veffel, with an empty and collapfedbladder communicating with it, though whenexpofed to air the gas flies off readily. The dimi-nution of abforption in increafed temperatures,Mr. Henry eftimates to be about T V of the whole,for every 10 degrees above 55°. With regardto the effedt of preffure, Mr. H. deduces fromexperiments, the general law, that “ under equal“ circumftances of temperature, water takes up« in all cafes the fame volume of condenfed gas,« as of gas under ordinary preffure.” There-fore as the volume of all aeriform bodies is al-ways inverfely as the comprefling force, thequantity of gas abforbed is directly as the pref-fure to which it is expofed; as, for example, ifthe common atmofpherical preffure, or that ofabout 30 inches of mercury, will caufe the ab-forption of carbonic acid equal in bulk to thewater, a preffure of two atmofpheres muft caufea double quantity to be abforbed.

The fpecific gravity-of carbonated water con-taining its own bulk of carbonic acid, is about1-0015. d B muft be taken in a low tempera-ture, otherwife the perpetual efcape of the gaswould defeat the accuracy of the experiment.

* Phil. Tranf. for 1803.

By freezing, the water parts with the whole ofits carbonic acid, juft before it folidilies.

Water readily parts with its carbonic acidby being heated, and in this way it is collectedin the analyfis of the carbonated mineral waters.To expel the whole it is requifite to boil thewater for ten or fifteen minutes.

The Angle teft of the acidity of carbonic acidby the change of vegetable colours, takes placewith the infufion of litmus, when added to car-bonated water. When the water contains asmuch as T V of its bulk of this acid gas, itchanges the blue of litmus to a red. e This ismoft conveniently {hewn by diluting the litmusinfufion till it is of a very faint blue, puttingfome of it into a glafs tube, and adding aboutas much of the carbonated water. If this iscompared with an equal quantity of litmus liquormixed with as much plain water in a flmilartube, the difference of colour will be very appa-rent. To fhew that the rednefs is produced bythe carbonic, and no other acid, let anotherportion be mixed with the carbonated water,previoufly boiled a few minutes to expel the acidgas, and no change of colour will now appear.

Lime-water is a much more delicate teft ofcarbonic acid, either in its gafeous ftate or unitedwith water, or even in combination with analkali. In all thefe cafes, whenever lime-watercomes in contact with carbonic acid, the limeeagerly abforbs it, and becoming thereby infolu-ble in mere water, it falls down in the form of'a fine white precipitate, rendering the watermilky, as when chalk is diffufed in water. Avery fmall portion of carbonic acid will produce'this effedt, and hence it is that lime-water be-comes cloudy and colledts a white pellicle onthe furface by mere expofure to air, the atmof-phere containing on an average about one percent, of carbonic acid. It is alfo very well fhewnby blowing air from the mouth through anyfmall pipe dipping in a glafs of lime-water. Thebreath contains about 5 or 6 per cent, of car-bonic acid, which prefently renders the lime-water entirely turbid. When the acid is infolution the power of this teft is equally great,difeovering-immediately, according to Bergman,about one cubic inch of the gas in 7000 grainsof water, being TT i w of the whole. It fhouldbe obferved however in ufmg this teft, that anexcefs of carbonic acid rediffolves the ftrft pre-cipitate of carbonat of lime, fo that there fhouldalways be an excefs of lime-water to engage allthe carbonic acid it meets with. Thus if a very

4 Bergman. * Ibid. ,

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vol. 1 .