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Nitrous Oxyd. The specific gravity ofthis gas is to that of hydrogen as 21. to 1; and1 00. cubic inches weigh between 48 and 49grains. When one cubic inch of nitrous oxyd ismixed with the same quantity of hydrogen andexploded by the electric spark, water is formed,and the only residue is one cubic inch of azote.Now as one cubic inch of hydrogen requireshalf a cubic inch of oxygen to become water,it follows that one cubic inch of nitrous oxydcontains one cubic inch of azote and half acubic inch of oxygen, condensed into the spaceof a single cubic inch.

In like manner, if dry charcoal be ignited inone cubic inch of nitrous oxyd, the productsare half a cubic inch of carbonic acid and onecubic inch of azote.. Hence, as oxygen neithergains nor loses in bulk by its conversion intocarbonic acid, the composition of nitrous oxydis found, as before, to be two volumes of azoteand one of oxygen, condensed into the space oftwo volumes. Hence too it consists, by weight,of 26 of azote and 15 of oxygen.

Nitrous Gas. Its specific gravity is to thatof hydrogen as 14 to I ; and 100 cubic inchesweigh about 32 grains. When several metals,such as arsenic, zinc, or potassium, are Heatedin nitrous gas, it oxydates them 1 and affordshalf its volume of azote. If charcoal is ignitedin two cubic inches of nitrous gas, the productsare one cubic inch of carbonic acid and oneof azote. Hence as oxygen gas neither ex-pands nor contracts by conversion into carbonicacid gas, nitrous gas consists of equal volumesof azote and' oxygen not condensed by theirchemical union; or it contains (by weight) 13parts of azote to 15 of oxygen. When twocubic inches of nitrous gas are exposed to theaction of nutriat of tin, or sulphuretted alkali,part of the oxygen of the gas is absorbed, andone cubic inch of nitrous oxyd is left, whichexactly harmonizes with their relative propor-tions of oxygen and azote; for one cubic inchof nitrous oxyd contains, as already mentioned,one cubic inch of azote and half a cubic inchof oxygen ; and therefore the portion of oxygenextracted by the sulphuret is exactly half acubic inch of oxygen.

Nitrous Acid Gas. When oxygen andnitrous gas are mixed together, red fumes ofnitrous acid gas are produced, and a conden-sation of the bulk of the gasses takes place. Ifthe experiment be made over water, a rapidand total absorption takes place, and the waterbecomes acidulous, Much difference of opinion

still exists as to the respective proportions iswhich nitrous gas and oxygen unite, nor is itvery easy to make accurate experiments, sincethe acid gas is absorbed both by water andmercury.

According to Sir H. Davy , when two vo-lumes of nitrous gas and one volume of oxygen,both previously dried, are mixed together in a'vessel exhausted of air, they become condensedto half their volume, and form a deep orange-coloured gas, which is nitrous acid gas. Cal-culating from the condensation, the specificgravity of this gas must be to that of hydrogenas about 28. to 1 ; and 100 grains of it mustweigh 65.3 grains. When water is admitted’to this gas there is a rapid absorption, and thewater gains a tint of green. This proportionof two volumes of nitrous gas to one volumeof oxygen is the highest in oxygenation thatcan be produced as a pure and distinct gasseousbody; for when the oxygen is actually mixedin greater proportion, the condensation is suchas only to indicate the formation of the above-nitrous acid gas, with an excess of uncombinedoxygen. The same happens when water isadmitted, the acid gas absorbed retaining nogreater a proportion of oxygen than when in agasseous state. But on the other Hand , whenthis nitrous acid gas is absorbed by an alkalinebase, a portion of nitrous gas is always evolved,leaving the remainder in a state of a higherrelative oxygenation than gasseous nitric acid.This the author concludes from many experi-ments to be in the proportion of 2 volumesof nitrous gas and If of oxygen, and this formsthe pale nitric acid as it exists in solution inwater, or as the acid part of the alkaline, earthy,and metallic nitrats. Nitric acid therefore, ac-cording to this opinion, when once obtained,from the decomposition of the nitrats can-exist unchanged in solution in water ; thoughwater alone cannot condense from its gasseous-state a mixture of two volumes of nitrous gasand If of oxygen, which is here given as thecomposition of nitric acid. This liquid acidagain may be made to absorb different quantitiesof nitrous gas, when it becomes yellow, orange,blue, and finally blueish-green, when saturatedwith ni.rous gas..

It has been mentioned that oxygen and ni-trous gas unite in different proportions, andthese are in a good measure regulated by thequantities of each gas employed, and the dia- •meter of the vessel in- which they are mixed;.Mr. Dalton gives the following interesting.re*.