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ftrong carbonated water and lime-water be mixedtogether at intervals, the mixture will becometurbid by the firft portion of carbonated water,then by more of the fame it will become quitetranfparent; then, a frefh portion of lime-waterwill again make it turbid; an excefs of carbon-ated water will again rediffolve the precipitateand make the liquor clear, and fo on alternately.

Barytic-water and Strontian-water are equallygood tefts with lime-water, and the two folutionsholding more of the refpective earths, they aremore active in their operation.

When carbonic acid gas is contained in anygafeous mixture, it is detected and readily ab-sorbed by the above-mentioned tefts, and thelofs which the whole gas experiences on beingfliaken with the tell, indicates the quantity ofcarbonic acid contained. A folution of caufticor femi-cauftic fixed alkali is a ftill better fub-ftance to abforb the carbonic acid gas, as it maybe made fo ftrong that a very fmall quantity ofalkali will take up a large portion of the gas, andthe full effect is immediately produced. Withthe alkali there is no cloudinefs or precipitateproduced, fo that the abforption is the only teftof the prefence of the acid gas.

It required the united efforts of many of thernoft eminent chemifts to prove that the famefubftance which exifts in a folid form in theliardeft lime-ftones, which gives the briflc tafteand fparkling appearance to mineral waters,which is entangled in the froth of fermentingliquids, which is generated in the lungs of allliving animals by refpiration, and which per-forms a moft important office in the fundtionsof vegetable life, is the fame that refults fromthe combuftion of charcoal and all carbonaceousmatters, and therefore, according to the univer-fally received theory of combuftion, is compofedof charcoal, the inflammable balls, united to aportion of oxygen fufficient to give it the pro-perties of an acid. The full difcovery and proofof this laft fact is due to Lavoifier, and fromthis elementary experiment he was able to de-duce the exa£t compofition of carbonic acid andthe proportion of its conftituent parts.

For this purpofe he introduced fome well-burnt charcoal into a large bell-glafs filled withoxygen gas, having previoufly kindled a minutepiece of tinder with an atom of phofphorus ad-hering to it and in contact with the charcoal.As foon as the charcoal took fire, it began toburn in the gas with a very bright flame, throw-ing brilliant fparks in every direction. The com-buftion flopped long before the whole of the1 An. Chem. tom. 39. c Prieftley. ■> P

oxygen was confumed, owing to the carbonicacid generated, and mixing with it; and hencetoo there was very little diminution of the entirequantity of gas, as takes place in the combuftionof phofphorus, and many other bodies where theproduct is folid or liquid. When all was cold,the carbonic acid was fubtradled from the re-fidue by means of cauftic alkali, the weight ofwhich acid was very exadlly equal to the unitedweights of the charcoal and the oxygen con-fumed, and by computing the proportions, of dietwo, it was found that carbonic acid is compofedof about 28 of charcoal and 72 of oxygen. Sub-fequent experiments by different chemifts agreevery nearly in the above proportions. Thofeof Clement and Defornies, f made with pickedcharcoal heated ftrongly for an hour in a co-vered crucible, and therefore in the pureft pof-fible ftate, give 28.6 of charcoal to 71.4 of oxy-gen. No tinder nor phofphorus were ufed tokindle it, for when any portion of the charcoalis heated red-hot in the air, the inftant the oxy-gen gas reaches it, the combuftion becomes bril-liant, fparkling, and rapid.

Carbonic acid is alfo produced by direct com-bination of carbon and oxygen when charcoal isdiftilled with the red oxyd of mercury; s whichmetallic fubftance diftilled without addition, isknown to yield a very large quantity of oxygengas.

Carbonic acid is at its higheft ftate of oxy-genation, and in any lower ftate it lofes its acidproperties. It is capable of decompofition eitherwholly or partially, furnilhing many very curiousexperiments in each procefs.

Phofphorus is the only fubftance by whichthe carbonic acid has ever been compleatly de-compofed by compound affinity, and its bafeleft in the ftate of charcoal. This difcovery isdue to Mr. Tennant, h and was followed by othervaluable experiments by Dr. Pearfon.

From the well known fact that the phofphoricacid cannot be decompofed by charcoal whenunited with lime (phofphat of lime not yieldingphofphorus by diftillation with charcoal) Mr.Tennant inferred that the united actions of phof-phorus and lime would be fufficient to decom-pofe the carbonic acid, and therefore that whencarbonat of lime was heated with phofphorus,the latter would abforb oxygen from the car-bonic acid, and be acidified at its expenfe. Heaccordingly put a little phofphorus into a glafstube, doled at one end and coated with fandand clay, and over the phofphorus fome pow-dered marble. The other end of the tube waslib Tranf. for 179X- ’ Fhil. Tranf, for 179*.