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gas was given out, and on encreafing the heatit came over in torrents. It contained a muchlefs proportion of carbonic acid than the laft,and towards the end it confifted of pure inflam-mable gas. The abfence of carbonic acid wasknown by its not rendering lime-water turbid.Part of the zinc was found in the metallic ftatefublimed in the neck of the retort.

In like manner the red oxyd of copper andcharcoal gave by diltillation, firft, a mixture ofcarbonic acid with inflammable gas, and at Ialt agas purely inflammable. The copper was foundreduced in fmall globules. Litharge and char-coal gave a fimilar refult, and the lead was re-duced. The oxyd of manganefe previoufly par-tially deoxidated by heating to rednefs, wasalfo mixed with charcoal and diftilled, and gavethe fame products.

The diitillation of charcoal and the fublimedoxyd of zinc was repeated by Deformes andClement, with particular attention to the quan-tity of produ£ts from a given weight of thematerials. The charcoal and zinc were firftheated feparately and examined. Common char-coal heated ftrongly gave a confiderable quan-tity of an inflammable gas, and about Vo of itsweight of water. After an hour nothing far-ther came over, fo that to enfure the perfectpurity of the charcoal, it Ihould be ufed hot froma crucible or other veffel in which it has beenheated to a full red heat for about an hour. Theoxyd of zinc gave nothing at all by being heatedpcrfe, fo that it may at any time be confideredas pure when previoufly freed from accidentalmoifture.

By experiment it was found that 1435 partsof zinc increafed by calcination to 1748 of whitefublimed oxyd, and hence it is inferred that 100parts of the white oxyd confill of 82.15 of metal,and 17.84 of oxygen. Thirty grammes (463grs. troy) of pure charcoal prepared as above,and ftill hot, were mixed with as much oxydof zinc (equal parts having been found to bethe proportions in which the carbonous oxyd isgiven with more eafe than when lefs charcoal isufed) and were put into a coated glafs retort, withan adopter communicating with lime water,through which all the gafeous products paffed.When firft heated, a fmall portion of carbonicacid appeared, rendering the lime water turbid,but this effect foon ceafed, and the gas waspurely inflammable. In five hours all the pro-duction of gas had entirely flopped, and the en-tire products of the operation were as follows;

grammes

Zinc fublimed in the retort . . 21.82

Charcoal remaining.26.60

Carbonic acid contained in theprecipitated lime-waterNine litres (16.9 wine pints) ofinflammable gas, weighing

58.84

Lofs.. x.16

60,00

Difox'jgcnathn of Carbonic acid.

Mr. Cruikfhank having repeated an experi-ment of Prieftley’s to obtain an inflammable gasfrom carbonat of barytes, and the grey oxyd ofiron, varied it in the following manner;

Equal parts of chalk (heated red hot previouflyfor ten minutes) and iron filings were mixedand heated in a retort as before. Abundanceof gas was given out, which confifted prettyuniformly of about one part of carbonic acid,and 5 parts of the inflammable gas.

An ounce of chalk, previoufly heated red fat-ten minutes, was mixed with as much zincfilings, and heated gradually in a coated glafsretort. A little carbonic acid came over at firft,but foon mixed with the carbonous oxyd, andwhen the contents were thoroughly red nothingbut the inflammable gas came over, and in pro-digious quantity. Examined at different periodsof the diftillation it was found perfectly in-flammable, and free from carbonic acid. Whencold, there was found in the neck of the retortfome of the zinc fublimed and oxydated, belowthis fome remaining metallic zinc, and at thebottom a crumbly mixture of unmetallic zincwith an imperfe£t lime.

Chalk with tin filings gave a fimilar refult.

In the above three experiments the carbonicacid was united to an earthy bafe before diftil-lation, and confequently it was expofed to thedeoxydating effett of the metallic filings in itsnafcent ftate, or at the moment of its affumingthe gafeous form, a ftate in which gafeousbodies are peculiarly fufceptible of chemicalchange, frequently even when the very famefubftances refufe to act on each other after theyhave once acquired the ftate of gas. Mr. Cruik-fhank found however that even carbonic acidgas could be decompofed by the metals, thoughlei's perfectly. It was feen in the. followingway. A quantity of dry chalk was introducedinto an iron retort, over which was rammed

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