223 



TABLE II. 



Vapour pressures of carbon dioxide at temperatures between 

 — 183O.0 and — 167O.04. 



j Pressure observed I 

 Temp. 'in baryes diminish-' Vapour pressure 



T- 273°. 09 ; cd by residual ; in baryes. 

 i pressure \ 



Calculated 



according to 



Nernst. 



by correcting for the thermal molecular pressure. This was done 

 by means of' the formula given, by IvtsUDSf.n : 



1 ] 



p, V'J 



where />, and p.^ arc the measured pressure and the real pressure 

 respectively, 7\ and 7\ the corresponding temperatures, 2/? the 

 dianicler of the vapour pressure tube and / tlie mean free |)alh 

 calculated from y/'. == 4. This relation was thus also applied in 

 conditions, where the mean free path is not well represented by 

 Sutukuland's formula'): this may, however, be considered allowable 



2R 



in view of the small iiitliiencc ot the term ■ — . 



It will be seen that the nuxin term of the correction is large: 

 but its value is accurately known and is in no way connected with 

 the additional coi-rection for / . The latter is only of importance in 

 the last measurements. 



It is possible by a suitable choice of the radius of the vapour 

 pressure tube R to make the additional correction so small, that it 

 may be entirely neglected. It is our intention to do this in fnture 

 experiments in order to become entirely independent of the small 



1) The circumstance that in llie exponenlial form the same factor is here used 

 for the residual prossiu'o, although llie substance to which tliis pressure is due, 

 is unknown, is of no importance wiiliin the limits of accuracy of the experiments. 



