196 OXYGENATED COMPOUNDS OF NITROGEN. 



The same reaction occurs, whatever ~be the relative proportions 

 of the two gases and the order of the mixture, in presence of con- 

 centrated alkaline solutions, and even of baryta water. Not 

 only do the ratios between the volumes of the gases establish 

 this fact, but analyses made on several grammes of matter have 

 shown that the proportion of nitrogen trioxide formed corre- 

 sponds to 96 or 98 per cent, of the nitric oxide employed. 



If the reaction occur without proper precautions being taken 

 to absorb the nitrogen trioxide, and particularly if it be 

 executed with anhydrous bodies, nitric peroxide is formed. 1 

 Nitrogen trioxide acid cannot exist for any length of time 

 except in the presence of the products of its decomposition. It 

 is this complex mixture, variable according to circumstances, 

 which constitutes the body called nitrous vapour, whenever 

 oxygen is not in excess. The same remark applies, moreover, to 

 the liquid acid, the purest nitrogen trioxide which has been 

 obtained (Fritzche ; Hasenbach), containing about one-eighth 

 of nitric peroxide, according to the analyses. Peligot has 

 for long insisted on this circumstance. 



In presence of an excess of oxygen, there is formed, or 

 rather there exists, only nitric peroxide, as is known from the 

 labours of Gay-Lussac, Dulong and Peligot, who obtained in 

 this way the crystallised acid. We will not dwell further 

 on this point, except to observe that, nitrogen trioxide being the 

 initial product of the reaction, even in presence of an excess of 

 oxygen, we are forced to admit that nitric peroxide results 

 from this nitrogen trioxide, combined afterwards with a second 

 equivalent of oxygen 



N 2 3 + = 2N0 2 . 



In a dry gaseous mixture, as well as in presence of water, 

 the formation of the two oxides takes place almost in- 

 stantaneously. Admitting, according to analogy, and in con- 

 formity with an approximate gaseous density given by 

 Hasenbach, that the formula N 2 3 represents two volumes, the 

 second reaction would offer this remarkable character, hitherto 

 unique in the study of direct actions, of a real gaseous com- 

 bination accompanied by increase of volume, three volumes of 

 the component gases furnishing four volumes. 



1 The experiments were made with a system of two concentric bulbs (see 

 p. 168) of known capacity, hermetically sealed, one containing dry oxygen, 

 the other dry nitric oxide, about 300 to 400 cms. The inner bulb is broken, 

 by a jerk, and the two gases are allowed to react. When the reaction is 

 complete, the point of the outer bulb is broken in a solution of potash of 

 known strength ; the nitrogen trioxide and nitric peroxide are absorbed with- 

 out affecting the nitric oxide. The nitrogen trioxide is absorbed without 

 change, as proved by the foregoing tests. Nitric peroxide in the state of 

 vapour is likewise completely absorbed, being changed according to a well- 

 known reaction into nitrogen trioxide and nitric acid. 



