288 NITROGEN. 



completely from any mixture. But notwithstanding this pro- 

 perty, nitric oxide cannot be employed with advantage in the 

 analysis of air or similar mixtures, for the contraction which 

 it occasions does not afford certain data for determining the 

 proportion of oxygen which has disappeared. Nitric oxide 

 is capable of combining with different proportions of oxygen, 

 a combining measure or 4 volumes of the gas uniting, in such 

 experiments, with 1, 2 or 3 volumes of oxygen, and forming 

 nitrous acid, peroxide of nitrogen or nitric acid, or several 

 of these compounds at the same time. 



This oxide of nitrogen, like the preceding, is a neutral 

 body, and has a very limited range of affinity. A substance 

 is left on igniting the nitrate of potash or barytes, which 

 was supposed to be a compound of nitric oxide with potassium, 

 or barium, but Mitscherlich finds it to be either the caustic pro- 

 toxide itself or the peroxide of the metal. But nitric oxide 

 is absorbed by a solution of the sulphate of iron, which it 

 causes to become black ; the greater part of the gas may be 

 expelled again by boiling the solution. All the soluble proto- 

 salts of iron have the same property, and the nitric oxide 

 remains attached to the oxide of iron when precipitated in 

 the insoluble salts of that metal. The proportion of nitric 

 oxide in these combinations is found by Peligot to be definite ; 

 one eq. of the nitric oxide to four of the protoxide of iron ; or, 

 the nitric oxide contains the proportion of oxygen required to 

 convert the protoxide into peroxide of iron.* Nitric oxide 

 is also absorbed by nitric acid. With sulphurous acid nitric 

 oxide forms a compound which will be more particularly no- 

 ticed under that acid. 



NITROUS ACID. 



Syn. AZOTOUS ACID (Thenard,) HYPONITROUS ACID (Turner.) 

 Eq. 477 or 38.2 ; NO 3 . 



The direct mode of forming this compound is by mixing 

 4 volumes of nitric oxide with i volume of oxygen, both per- 

 fectly dry, and exposing the mixture to a great degree of cold. 

 The gases unite and condense into a liquid of a green colour, 

 which is very volatile, and forms a deep reddish yellow coloured 



* An. de Ch. et de Ph. t. 54, p. 17. 



