( 588 ) 



point curves, they are seen to touch each other at tlie end (critical 

 point of pure carbon dioxide) in agreement with Comni. X^ 81 

 §§ 9 and 14 (Proc. Oct. 1902). In the investigated part tiie curves 

 do ]iot show the point of inflection found by Verschaffelt with 

 mixtures of hydrogen and carbon dioxide (Comni. N". 47 Proc. Feb. 

 1899) ; they are ahvays concave towards the T-axis. 



Physics. - — ''IsothermaU of mivtures of oxygen and carbon dioxide. 

 r. hothermab of mivtures of the molecular compositions 0.1047 

 and 0.1994 of oxyijen, and the comparison o f them with those of 

 pure carbon dioxide." By W. H. Keesom. Communication N". 88 

 (6'^^ part) from the Physical Laboratory at Leiden, by Prof. 

 Kamerlingh Onnes. 



(Communicated in the meeting of November 28. 1 903). 



\ 5. According to § 4 (p. 586) the observations allowed of a 

 more accurate determination of the data for the critical point of 

 the mixtures for the range of the larger volumes and the range of 

 temperatures over which the observations have been made, in the 

 sense as it has been explained there, than it was possible from the 

 drawing given tliere. To this end diagrams were projected on 

 double the scale for the points in the homogeneous area for which the 

 volume is larger than 0.005 ; in these diagrams 0.0005 is represented 



by 1 mm. l^oth for log — and for log v. To determine the relation 



of the critical pressures independently and to test the relation of the 



critical temperatures of mixtures to that of pure carbon dioxide, 



pv 

 diagrams were constructed for the same area, where log — is drawn 



as a function of log p; here 1 mm. represents: on the log p-axis 



0.00025, on the %^-axis 0.0005. 



§ 6. The diagram for the mixture which had been transferred on 

 tracing paper and in the middle of which a cross of axes was drawn 

 in order to permit an accurate judgment of the agreemeiit of the 

 systems of axes for the two diagrams, was placed over the diagram 

 for carbon dioxide, so that the log v-, and log y>-axes respectively 

 coincided, and then they were shifted until to the eye the isother- 

 mals of the mixtui-e coincided with the svstem foi carbon dioxide. 



