32 Mr. V. H. Veley. The Conditions of the [June 2, 



It is manifest from the figures given in the tables above that 

 sample No I was decomposed to some extent at 58, and to a greater 

 degree at 100, sample No. II at 120, sample No. Ill at 155 U , and very 

 rapidly at 195, sample No. IV at 195, while the most dilute acid 

 remained practically unaltered throughout. Ib would also appear 

 that, provided every care be taken to eliminate reducing substances, 

 especially of an organic character, and provided also that the acids 

 are not unduly exposed to sunlight, nitric acid is more stable than 

 former experience indicated. It would be an interesting subject of 

 enquiry to ascertain as to whether nitric acid is affected by shocks, 

 as I have found that samples of acid purified so as to be practically 

 free from nitrous acid were contaminated with that impurity after a 

 railway journey. 



Formation of Nitrous Acid from Nitric Oxide and Nitric Acid. 

 It is a common matter of observation that when nitric oxide gas is 

 passed into nitric acid a greenish-blue solution is produced, which 

 shows all the reactions of nitrous acid ; some writers, however, con- 

 sider that the nitric oxide gas is only dissolved as such in the nitric 

 acid in that, when the liquid is warmed, the gas is again evolved. It 

 is more probable that nitrous acid is formed and subsequently decom- 

 posed, changes represented by the following equations : 



(I.) 2NO+HN0 3 +H 2 = 3HN0 2 . 

 (II.) 3HN0 2 = 2NO + HN0 3 +H 2 0. 



Clemente Montemartini* has proved that of these changes the 

 latter proceed quantitatively, at least in dilute solution, in accordance 

 with the equation given. 



If these changes are strictly reversible, it would follow as a 

 necessary consequence that there would be a limit to the amount of 

 the nitrous acid produced, and this limit would be dependent upon 

 conditions such as concentration of acid and temperature. The equa- 

 tion for equilibrium will be 



pjq = constant, 



wherein p is the mass of nitric acid, and q is the mass of nitrous 

 acid, for when the limit is reached the amounts of nitric oxide gas 

 passing in and out would be identical, while the alteration of the 

 mass of water would be immaterial. 



On the other hand, if the phenomenon is merely that of solution, 

 the amount of nitric oxide gas dissolved should, other conditions 

 remaining the same, diminish under all circumstances as the temper- 

 ature increases. 



* ' Home, Accad. Lincei Eendiconti,' 1890, p. 264. 



