536 Observations on some ComUnalions of Azote ivilh Oxygen, 



I hen see the water successively become a greenish blue, a dark 

 green, and an orange-yellow. Tliese variations of colour are 

 the same with tliose which have been so long observed in the 

 iiitric acid of ditferent degrees of concentration, uhe« we pass 

 into it nitrous gas of variable pro])ortions. It seems, therefore, 

 that this gas acts, in this last case, by bringing back a portion 

 «L»f nitric acid to the state of nitrous acid, and passing itself to 

 this state. As to the nitric acid wliich is fountl mixed in very 

 different proportions with these various con)binations of oxygen 

 and azote, according to the manner in which they have been 

 obtained, it does not seem to affect their colours sensibly; at all 

 events, it will not be correct to suppose that these mixed acids 

 are only simple mixtures ; for the nitrous acid seems to have an 

 affinity for nitric acid, if we jud^e according to the recent ob- 

 servations of Mr. Davy, on the properties of the nitro-muriatic 

 acid. 



The aiihvdrated nitrous acid, when placed in contact with a 

 strong solution of potash, is decomposed ; nitrous gas is extri- 

 cated, but in smaller quantity than when the same decomposi- 

 tion is produced by water: — nitrite and nitrate of potash are 

 formed. With liijuid ammonia, the action is extremely violent, 

 iindthe nitrous gas extricated is mixed with azote ; — this proves 

 that a part of the annnonia has been decon)posed. 



When we pass nitrous acid in vapour over dry caustic barytes 

 placed in a tut)e at the common temperature, the vapour is 

 tlowly absorbed ; but at a temperature of above 200" the barytes 

 suddenly becomes incandescent, and no elastic fluid is extricated. 

 The combination which results melts, and is afterwards very 

 difficult to dissolve: — we therein find once more nitrate and 

 nitrite of barytes. It is certainly a very remarkable phEenome- 

 non, and the explanation of which is not very easy, to see the 

 %arytes transformed into nitrate and nitrite, at a temperature 

 which seems to be very superior to that which will be necessary 

 to decompose those two salts when once formed. 



I have endeavoured to determine the action of the different 

 combustible bodies on the nitrous acid when reduced into vapoury 

 but all the phrenomeua which I have oliserved may easily be 

 foreseen by the theory, and this saves me the trouble of relating 

 them. I shall merely say, that ail these experiments confirm 

 the opinion that the nitrous acid yields, less easily than the eu- 

 chlorine, the oxygen which enters into its composition: iode, for 

 instance, may be sublimed into this vapour without receiving 

 any alteration from it: sulphur and even phosphorus require, in 

 order to inflame, a higher temperature than in pure oxygen. 



The anhydrous nitrous acid is combined, without undergoing 

 decomposition, with the concentrated sulphuric acid ; and it i> 



probable. 



