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PROOFS OF THE PROPERTIES OF NITROUS GAS.

Experiment IV.

Nitrous gas is absorbed by nitric acid, to which it gives newcharacters.

Let nitrous gas pass as it is liberated from the materials whichafford it, into a bottle containing colourless nitric acid, the acidwill first become yellow, then green, next orange-coloured, andat last dark olive-coloured and fuming.

Rationale. ..The change of colour depends on the absorptionof different quantities of nitrous gas. Priestley found that 100parts of nitric acid of a moderate strength, absorbed in two days9O.29 of nitrous gas He informs us that when about sevenparts were absorbed, die acid assumed an orange colour; wheneighteen parts were absorbed, a green colour; and diat whenthe 9O.29 were combined, it became red and fuming.

Remark. ..If the olive-coloured acid be diluted with water, itbecomes blue; the orange-coloured when united with waterbecomes emerald-green ; and a large quantity of water renderseither of them colourless.

Experiment V.

Nitrous gas which has been absorbed by nitric acid may be ex-pelled again from this fluid.

This may be shown by gently heating the acid coloured in thebefore-going experiment till it becomes limpid. In this experi-ment light should be excluded.

Rationale. ..The nitrous gas absorbed by die acid has agreater affinity for caloric than the nitric acid lias; this propertytherefore is here employed for disengaging the nitrous-gas whichrendered the acid fuming.