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oxygen from common air, fo that the fameexperiments which fncceed in common eudio-metric procefl'es will often convert nitrous gasinto nitrous oxyd.

The fulphite of potafh effects this changewith greater rapidity than any other fubftance.Mr. Davy found that at temperature 46°, 16cubic inches of nitrous gas were converted inlefs than an hour into 7.8 inches of nitrousoxyd by about ieo grains of pulverized fulphiteof potafh, retaining its water of cryftallization.This appears to aft by the finipleft poffibleaffinity, namely that of the fulphite for thatpart of the oxygen which makes the differencebetween nitrous gas and nitrous oxyd. Theazot with which nitrous gas is always mixedremains unaltered.

Nitrous gas expofed to dry muriat of tin isflowly converted into nitrous oxyd, apparentlyby the fame Ample affinity as by the fulphites.

All the dry fulphurets produce the famechange on nitrous gas in about the fame timethat they would require to deoxygenate commonair.

Iron filings and fulphur mingled togetherand moiftened produce the fame effeft onnitrous air, and the change is effefted in abouttwelve hours.

Iron filings alone produce the fame change,which was Dr. Prieftley’s firft experiment bywhich he difcovered this gas.

The prefence of moifture has been fuppofedneceffary to the fuccefs of the experiment, butthis does not feem to have been the cafe. Dr.Prieftley filled a half pint phial with nails andthen' with quickfilver, after which the latterwas difplaced by nitrous gas, and the phial wasleft with its mouth Handing over mercury.

No moifture was intentionally introducedhere, but in the courfe of two months the gaswas converted into nitrous oxyd. Dr. Prieftleyhowever adds that when the procefs is carried onover water the change is effefted in a few days.

When dry nitrous gas and dry fulphurettedhydrogen are mixed together over mercury amutual decompofition flowly takes place. 0 Thegaffes are diminifhed, fulphur is depofited,nitrous oxyd is formed, and Cgns of the pro-duction of ammonia and water are perceived.

As the fulphur is depofited in this experi-m e jtt, and no fulphuric acid produced, thehydrogen muft be the foie deoxygenating agent,but as fome ammonia is produced, a portion ofthe azot of the nitrous gas muft alfo be feparatedto contribute to the formation of the alkali. A

c Davy. * Prieftley.

part of the hydrogen therefore appears to unitewith the excefs of oxygen of the nitrous gasand forms water, and another part of it with aportion of the azot of the nitrous gas forms theammonia. But the removal of this azot fromthe nitrous gas would have a direft effeft inpreventing its converfion into nitrous oxyd, andtherefore the abftraftion of its oxygen muft begreater in this than in the Ample decompoAtionsof nitrous gas, and the entire quantity of nitrousoxyd produced fliould be Jefs. There is toomuch variation however in the different experi-ments to allow of much accuracy of refultswith thefe complicated agents.

Zinc Alings convert nitrous gas into nitrousoxyd with as much cafe as iron Alings, butoniy when in contaft with water. Ammoniais produced and the zinc is changed to a whiteoxyd, which can only be explained by thefuppoAtion of a double decompofition of thewater and the nitrous gas, the latter yieldingpart of its azot to part of the hydrogen of thewater for the ammonia; part of its oxygen tothe remainder of the hydrogen in order toproduce the change from nitrous gas to nitrousoxyd; and the oxygen ariAng from the decom-pofed water uniting with the zinc.

Another method of producing nitrous oxydhas been ftated to be during the folution offeveral of the metals in nitric acid under parti-cular circumftances of concentration, heat, &c.The gas in this cafe is always mixed withnitrous gas, and often with azot. The metalsfrom which it is produced with the greateft eafeare iron, zinc, and tin. Iron produces avariable mixture of nitrous gas and nitrousoxyd. If a cold faturated folution of nitrat ofiron is heated, much nitrous oxyd is produced.*A great quantity of it is alfo given out byadding iron filings to nitrat of iron, and thefilings pafs to the ftate of black oxyd, asBerthollet has obferved. When tin is diffolvedin concentrated acid of about 1.4 fp. gr. (whichis nearly as ftrong as is able to aft on thismetal) the gas is a mixture of about one part ofnitrous oxyd with two of nitrous gas, and a veryfmall quantity of azot. With an acid of 1.24the proportion of nitrous oxyd is greater, andincreafes to about | of the whole towards theend of the procefs.'

Zinc alfo yields this gas during the aftion ofnitrous acid of any fpecific gravity, and in moftabundance when the acid is dilute, and towardsthe middle and end of the procefs. The nitratof zinc whilft diftilling to drynefs gives much

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