Change of Oxygen into Ozone. 211 



The phenomenon would be explained if we supposed that in 

 the very unstable state of the gas at a pressure near "7 

 millim., where a mere change of volume suffices to dissociate 

 some of the 3 molecules, during the dissociation a number 

 of free ions of were liberated, and on account of slight want 

 of electrical neutrality in the apparatus only in the one 

 gauge. We have therefore to consider the effect of a number 

 of atoms charged with electricity when mixed with a number 

 of molecules. The atoms repelling one another on account 

 of their electric charges will tend to accumulate near the 

 walls of the vessel, while the molecules will remain evenly 

 distributed through the vessel, for if they did not a diffusion 

 stream would be set up in them until they were uniformly 

 distributed. Thus then we can separate the mixture in 

 imagination into two media determining the distribution of 

 partial pressure amongst the atoms as if the molecules were 

 absent, and then adding the uniform partial pressure due to 

 the molecules. The differential equation for the distribution 

 of pressure amongst atoms in a spherical vessel is easily 

 written down, but I will defer its discussion to a more appro- 

 priate occasion. For the present it will suffice to say that 

 obviously the effect of electrical repulsion will be to force 

 the majority of the atoms out to the surface, where a layer 

 of rapidly altering density and pressure will be formed 

 merging into the more gradually altering body of the 

 medium. Let us consider the exaggerated case where, in 

 the surface-layer, the pressure increases from one side of it 

 to the other by P; then if Q is the total charge of the whole 

 layer of surface 4-7rR 2 , the repulsion experienced by unit area 

 of the layer is (Q/R 2 ) (Q/4ttR 2 ), which is to be equal to P. 

 If, then, in Baly and Ramsay's experiments in one of the 

 gauges at the moment at which they were isolated from one 

 another the value of P, due to free oxygen ions in it, was 

 about 8/9 of the recorded initial pressure of about '75 millim. 

 then the mass of oxygen in this gauge, with the assistance of 

 the ions, could equilibrate the pressure due to nine times as 

 great a mass of oxygen in the other gauge, for we shall see 

 immediately that the mass of the ions is negligible. Sup- 

 posing Baly and Ramsay's cylinder of 90 cub. centim. to be 

 replaced by an equal sphere, then R is 2*78 centim., and P 

 being 8/9 of °001 atmo is in round numbers 889 dynes per 

 sq. cm., and therefore Q in absolute electrostatic units is 817. 

 Now the electrochemical equivalent of oxygen is -00082, that 

 is, there is one absolute electromagnetic unit of electricity or 

 3 x 10 10 electrostatic units in '00082 gram of oxygen ions, 

 and therefore the mass of the ions containing our charge of 



