NITRIC OXIDE. 287 



Or in symbols : 



4NO 5 and 3Cu=3(Cu O, NO 5 ) and NO 2 . 



Properties. This gas is colourless, but when mixed with air 

 it produces ruddy fumes of the peroxide of nitrogen. It is 

 irritating, and causes the glottis to contract spasmodically 

 when an attempt is made to respire it. Nitric oxide has 

 never been liquefied : water at 60 according to Dr. Henry, 

 takes up only 5 or 6 per cent of this gas. It is formed of one 

 combining measure of nitrogen or 2 volumes, and two com- 

 bining measures of oxygen or 2 volumes, united without con- 

 densation, so that the combining measure of nitric oxide 

 contains 4 volumes. The weight of one volume, or the density 

 of the gas, is therefore 



976+976 + 1102.6 + 1102.6 ir voQ Q 



1 Uo 7 . O 



This gas is not decomposed by a low red heat. 



Many combustibles do not burn in nitric oxide, although 

 it contains half its volume of oxygen. A lighted candle and 

 burning sulphur are extinguished by it ; mixed with hydrogen, 

 it is not exploded by the electric spark or by flame, but it 

 imparts a green colour to the flame of hydrogen burning in 

 air. Phosphorus and charcoal, however, introduced in a 

 state of ignition into this gas, continue to burn with increased 

 vehemence. The state of combination of the oxygen in this 

 gas appears to prevent that substance from uniting with com- 

 bustibles, unless, like the two last mentioned, they evolve so 

 much heat as to decompose the nitric oxide. Several of the 

 more oxidable metals, such as iron, withdraw the half of the 

 oxygen from this gas, when left in contact with it, and convert 

 it into nitrous oxide. 



No property of nitric oxide is more remarkable than its 

 attraction for oxygen, and it may be employed to separate 

 this from all other gases. Nitric oxide indicates the presence 

 of free oxygen in a gaseous mixture, by the appearance of fumes 

 which are pale and yellow, with a small, and reddish brown 

 and dense with a large proportion of the latter gas ; and also 

 bv a subsequent contraction of the gaseous volume, arising 

 from the absorption of these fumes by water. Added in 

 sufficient quantity, nitric oxide will thus withdraw oxygen most 



