1892.] Formation and Decomposition of Nitrous Acid. 



47 



In all the above series of experiments the observed and calculated 

 results are as nearly approximate as can be expected, considering the 

 great instability of the nitrous acid, which is appreciably decomposing 

 even in the brief interval of time required for the transference of the 

 solution from the decomposition flask into the potassium permangan- 

 ate. In the last series of experiments quoted above, in which a 

 considerable proportion of nitric acid was purposely introduced, it is 

 to be noticed that the rate of decomposition is decreased, even though 

 the mass of nitrous acid originally present was greater, which should 

 of course produce an exactly opposite result. This would, therefore, 

 seem to indicate that nitrous acid is more stable in the presence of 

 excess of nitric acid. 



Nitrous Acid from Nitric Oxide and Nitric Acid. 



Nitric oxide gas was passed into concentrated nitric acid until a 

 deep green liquid was obtained ; 10 c.c. of this were then slowly 

 introduced into about five times its bulk of water, and the whole 

 volume finally made up to 100 c.c. 



Series XXVII. 



Volume of solution = 100 c.c. Temperature, 27'70'1. 

 Ratio of nitrous to nitric acid = 1 : 10" 1. 



The curve representing the course of decomposition of the nitrous 

 acid obtained by this method is precisely identical with that of the 

 nitrous acid from the silver nitrite ; though the rate of decomposition 

 is somewhat diminished. For if the series above be compared with 

 Series XXV, which lasted for the same duration of time, yet though 

 the mass undergoing change was nearly twice as great, and the tem- 

 perature 2 higher, both of which conditions would increase the rate, 

 yet there is a difference of only 5 per cent, in the amount of nitrous 



