Vibrations set up in Molecules hy Collisions, 27& 



In all these sets of results the differences between the 

 values in the third and fourth columns respectively are also 

 within the limits of experimental error. 



Example III. The decomposition of ammonium nitrite in 

 aqueous solution into nitrogen and water, as being in accor- 

 dance with monomoleciilar law, is also analogous to the case 

 cited above, but at present difficulties have been experienced 

 in fixing the conditions for obtaining a sufficient number of 

 observations to apply the above equation. It has only been 

 found possible to obtain at most two or three observations 

 unless the volume of gas collected in each single observation 

 is so small that the experimental error is thereby greatly 

 increased. 



Other examples of the above phenomena that have been 

 observed are the decomposition of oxalic acid and of potassium 

 ferrocyanide by concentrated sulphuric acid, but as regards 

 both of these the formation of more than one gas within the 

 solution renders the problem more complicated. The rate of 

 evolution of oxygen from solutions of peroxides would pro- 

 bably present a similar and simple case, and others might also 

 be cited, but in this communication it is only desired to point 

 out a possible line of investigation upon the earlier stages 

 of chemical reaction, which appear to be too often dismissed 

 as inconsequent. 



XXXV. On the Vibrations set up in Molecules by Collisions. 

 By J. H. Jeans, Ji.A., Isaac Neicton Student and Fellow 

 of Trinity College, Cambridge*. 



§ 1. 4 STEEL ball dropped on to a rigid steel plate will 

 Jl\. rebound perhaps half a dozen times before its 

 energy is appreciably lessened ; this is because of the great 

 elasticity of steel. If the kinetic theory of gases is true, a 

 system of molecules must rebound from one another and from 

 rigid walls many billions of times before the total energy is 

 appreciably lessened. The aim of the present paper is to 

 show that, in so far as the data available enable us to 

 judge, molecules will possess sufficient elasticity for this to 

 occur. 



§ 2. Let us suppose that a molecule possesses, in addition to 

 its motions of translation and rotation, small vibratory motions 

 of which the oscillations are, in the cases we have to consider, 

 so small as to be isochronous. Then the kinetic and potential 



* Communicated by the Author. 



