404 Mr. W. M. Hicks on some Effects of Dissociation 



time not many more of its own are ; therefore, since the com- 

 binations of A and B atoms into C molecules are destroyed 

 more slowly than the combinations of A and B atoms into A 

 and B molecules, the gases A and B after a time change 

 into C. 



5. In a similar manner we may explain the result obtained 

 by Andrews, that if nitrogen be mixed with carbon dioxide, 

 the mixture may be subjected to very high pressure without 

 the carbon dioxide being condensed. When a gas condenses, 

 we must suppose that molecules combine with molecules to 

 form larger aggregations, and that this continues until the 

 whole gas is condensed into a liquid. When the temperature 

 is below a certain degree, the change from the gaseous to the 

 liquid state takes place around nuclei, in which the molecules 

 get entangled, and which the energy of agitation is not great 

 enough to destroy ; in this case a mist is formed, and we see 

 the gas condense. But when the temperature is higher than 

 a certain degree (the critical temperature), the energy of 

 agitation is so great that an aggregation greater than the 

 average gets broken up as soon as formed, and the gas passes 

 into the liquid form by having its particles uniformly pressed 

 more closely together ; no separate nuclei are formed to 

 diffuse the light passing through, and we can see no change 

 take place. The nitrogen molecules and atoms act in the 

 same way to break up the carbon dioxide aggregations as 

 soon as formed, and hence prevent it from condensing. 



6. The fact that two states of a gas are possible under the 

 same conditions, as for instance 2N + and N 2 0, is easily 

 explicable, as it is quite clear that in general there will be 

 more than one way in which the losses of the different 

 molecules may be equal to their gains, In other words, the 

 equations of high order, which we obtain, have several positive 

 roots, which give a stable state of the gas : as the tempera- 

 ture rises, one such state may become unstable ; in this case 

 we shall get a sudden change into one of the other stable 

 states, with a transformation of energy, answering in ex- 

 perience to an explosion with evolution of heat. 



II. 



7. Let N be the number of molecules of mass m^ in unit of 

 volume, and N' the number of molecules of mass m 2 . Also 

 let a, /9 be the velocities of mean square in the two systems 

 respectively, and s .the mean effective distance between mole- 

 cules of the first kind and of the second. 



Consider a molecule of the first kind moving with velocity v; 

 the number of such whose velocities lie between v and v + Sv 



