893 



the nitrogen side) is only very faintly curved ') had been found 

 before in a series of unpublished pi-eliminary determinations and 

 may be looked upon as an indirect confirmation of our observations 

 respecting the vapour-pressures of nitrogen (IV. 2). 



The /«'-diagrams shows that especially on the nitrogen-side, the 

 values of the composition of the liquid and vapour phases do not 

 differ much from each other. This would lead to the expectation 

 that the fractionation, especially of the mixtures with little argon, 

 will not be a very easy matter. 



When the change with pressure of the composition of the phases 

 is taken into consideration, it follows tiiat the differences in com- 

 position increase with diminishing pressure, so that a comparison of 

 the T-,r diagram for argon -nitrogen at 76.0 cms with B.\ly's dia- 

 gram '') for the fractionation of air |)iits the problem of the frac- 

 tionation of the mixtures in question in a less unfavourable light. 

 At the same time it follows from our results, that the use of mixtures 

 with little argon will give considerable difficulty. 



VII. Resume'. 



1. A method was worked out enabling us to determine the 

 composition of argon-nitrogen mixtures with an accuracy of 0,1 7» 

 or, if need be, higher. 



2. A systematic difference was found between the results of the 

 determinations with the baroscope and the method referred to under 

 1, which led us to the conclusion, independently of ScHUt.TZE's work 

 (I.e.), that the atomic weight of argon hitherto assumed might not 

 be quite exact. As this systematic difference disappears when 

 Schultzk's value is adopted, the latter is thereby rendered highly 

 probable. A preliminary direct determination gave a value in good 

 agreement with Schultze's result. 



3. New measurements of vapour-pressures for oxygen, argon and 

 nitrogen are published and critically compared with those of previous 

 observers. The triple point of argon was determined with greater 

 accuracy. 



4. The end-points of condensation of the argon-nitrogen mixtures 

 were determined with an accuracy corresponding to 0.02° in the 

 temperature. 



1) Pointing to a simple behaviour of argon towards nitrogen. 



2) Phil. Mag. 49 (1900) p. 517. 



