520 



not yet completely inonatoinic, whereas at the higher temperatures 

 much iiigher critical reduction-temperatures have undoubtedly to be 

 used, no weight can be attributed to the latter determination. 



2. Oxijgen (Amagat). 



The isothermals — J98°.4;vt' '^i"^ 0\ coincide, so that, v/ith 

 %0, = — 118°. 84 C. (according lo Kameri.ingh Onnks, Doksman and 

 Holst), 



Ok.Ne^ -230.°9 C, 7V.We= 42.^2 K. 



3. Aiyoii (Kamkrungh Onnes and Ckommelin). 



a. The isothermals — 21 7". S^^^ and — 87°.05^r coincide. With 

 OkAr^= — 122 .44 C according lo Crommeun this leads to: 



Ö,,.;,, = -22>\°2 C, 7',.;v. = 44^9 K. 



b. The isothermals — 200.°!;^^ and — 28°,i,. coincide; hence 



0,j,, ^ -228.^2 C, T,.^, = 44.°9 K. 



c. The isothermals — 191';/^ and 0°j,. coincide; which yields: 



ü^,Ne= -227.°9 C, and '/Vat. = 45.°2 K. 



It will be seen that on the one hand the two values obtained 

 from iiy drogen and o.xygen and on the other the three values from 

 argon agree closely, the mutual agieenient between these two groups 

 of values being much less perfect. 



if, using the critical temperature as obtained by the comparison 

 with argon, the data of Table IV are plotted in the diagram of 

 reduced vapour-pressure curves (p as function of ', where f is the 

 reduced temperature for the several substances) and in that of the 

 reduced liquid- (and vapour-) densities (Comm. ISlrt tig. 3 Oct. 1912) 

 respectively, the curves for iieon range themselves very well between 

 those of the other substances in their proper order. 



Neon thus appears to correspond closely with argon and 

 to deviate from it in the direction indicated by its lower critical 

 temperature. We hope to be able soon to be in a position to com- 

 municate fuller data regarding the equation of state of neon, especially 

 to replace the preliminary measurement of the critical pressure by 

 a more accurate one and to give a direct determination of the critical 

 temperature. 



We are glad to I'ecord our thanks to Mr. P. G. Cath for his 

 assistance in the investigation of the liquid state of neon. 



