[miller-kenrick] researches IN PHYSICAL CHEMISTRY 213 



on the assumption of equilibrium, using Bodlander and Storbeck's 

 value for the equilibrium constant. {Jour. Phys. Chem. 14 pp. 885- 

 908, 1910). 



No. 14. W. L. Argo: — The velocity of sound in nitrogen dioxide 

 gas. — The relation between the piessure, temperature and density of 

 nitrogen peroxide is satisfactorily expressed by the statement that 

 there is equilibrium between two gases with formula weights corres- 

 ponding to N2O4 and NO 2- Up to the present no experiments have 

 indicated that any appreciable time is required for establishing equi- 

 librium after an alteration of pressure. The object of Mr. Argo's 

 investigation was to ascertain whether, in extremely rapid changes 

 of pressure, any evidence of incomplete equilibrium could be ob- 

 tained. 



Since the peroxide dissociates according to the equation 



N2O, = 2 NO2 



the adiabatic changes of pressure due to stationary sound waves will 

 cause local dissociation and association. The actual behaviour of the 

 gas under such changes of pressure will confoim to a condition which 

 lies between those represented by the two following limiting assum- 

 tions, viz: — (a) that the dissociation is so rapid that complete equi- 

 librium exists at every moment in spite of the sound waves, and (6) 

 that the rate of dissociation is so small that no change in dissociation 

 takes place during the rapid change of pi essuie. 



The change of density with pressure, dp.' dp, may be calculated 

 for each of these two assumptions and compared with the actual 

 value found experimentally from the velocit}' of sound in the gas. 



Since nitrogen peroxide attacks rubber and many metals, a modi- 

 fication of Kundt's apparatus for determining the velocity of sound had 

 to be devised. An apparatus was constructed entirely of glass and 

 platinum, and graphite powder was used for producing the dust 

 figures. The only two experimental results obtained up to the pres- 

 ent, gave a value for dp! dp lying between those calculated from the 

 assumptions (a) and {h) above. It seems probable, therefore, that the 

 reaction between the two forms of the peroxide is not instantaneous.* 



It is proposed to continue these measurements, and to determine 

 if possible whether traces of water vapour have any effect on the 

 rate. (Wintei 1911-1912). 



*Since this article was sent to press Mr. Argo has completed the investigation. 

 The results show definitely that the rate of dissociation is so great that there is no 

 appreciable "lag" in the reaction following changes of pressure caused by the sound 

 waves, in the case of both dry and moist nitrogen peroxide. 



The results will appear shortly in The Journal of Physical Chemistry, Vol. 18. 



