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



Summary of .Results. 



I. The reaction between nitric oxide and nitric acid varies with 

 the concentration of the acid and the temperature ; with more con- 

 centrated acids nitrogen peroxide is at first formed and then nitrous 

 acid ; with less concentrated acids the latter is produced at once. 



II. Only with quite dilute acids (of 30 per cent, concentration and 

 below) does the reaction between the nitric oxide and nitric acid 

 appear to be reversible ; the average value for p/q = 9 (p = quantity 

 of nitric, q of nitrous, acid), though the actual value varies from 

 3 to 4 per cent, on either side, according to the conditions of the ex- 

 periment. 



III. With more dilute acids the amount of nitrous acid formed at 

 first increases slightly and then decreases with the temperature ; but 

 with more concentrated acids the amount uniformly decreases. 



IV. The proportional quantity of nitrous acid formed increases 

 with decrease of concentration, but the actual quantity is of course 

 less. 



It would appear that the simple reversible reaction between nitric 

 oxide and nitric acid becomes modified with acids above a concentra- 

 tion of about 30 per cent, and a temperature of 32. These were also 

 approximately the limits of concentration and temperature, above 

 which the reactions between metals and nitric acid could not be 

 prevented by substances such as urea, potassium chlorate, and the 

 like. I will, however, merely allude to the point without wishing to 

 lay an undue stress upon possibly nothing but chance coincidences. 



The Bate of Decomposition of Nitrous Acid. 



The velocity of the decomposition of nitrous acid, presumably in 

 nitric acid solution, has been made the subject of a previous investi- 

 gation by Clemente Montemartini (vide supra). As a result of 

 several series of experiments this writer considers that the rate of 

 this decomposition may be expressed by the differential equation 





or 



in which C is the concentration, T the time, and & is a constant. 



This equation will be discussed in the sequel. My experiments 

 were commenced primarily with a view of ascertaining if nitrous acid 

 is the more stable the greater the proportion of nitric acid present, 

 a point which was raised in the course of my investigations on the 

 reactions of nitric acid and metals. Further, it seemed probable that 

 the presence of metallic salts might also affect the stability of nitrous 

 acid, as Armstrong and Ac worth* allude to the persistence with 

 * ' Cbem. Sec. Journ./ 1877 (II), p. 54. 





