456 



lil filling II a is calculated by interpolation between calibration 

 points 20°, 24 and 4°, 07 K., b by using only tlie calibration point 

 20°, 24 K. in the same way as in filling I only calibration point 3°,60K. 

 needed to be used. 



The agreement between the measurements with filling I and II 

 is bad. If in filling II we calculate, with the pressure increase 

 of 10,3^ mm. per degree, the temperature of the helium on May 

 28^'', 1920, the calculation yields 4°,27 K, while the vapour pressure 

 gave 4°, 22 K (table II); this is in favour of the measurements on 

 May 28^'\ If we further take the large Aif's in filling I into 

 consideration, a determination with filling I deserves less confidence 

 than one with filling II. We take T vanishing point lead = 7°,2 K, 

 although it is still desirable to make a more accurate determination. 



§ 5. Comparison of the vanishiny point temperatures of lead and 

 uranium lead {Ra G). 



On May 18^^, 1920 the cross-thread of the kathetometer was 

 adjusted to the mercury meniscus in the open tube of the thermo- 

 meter at the pressure belonging to the vanishing point temperature 

 of Pè-1919-/ (the meniscus in the closed tube must of course always 

 be kept on the same mark). 



After a decrease of temperature Isotope /^è-1919-/ was inserted 

 in the resistance circuit and the temperature again raised. If the 

 galvanometer moved, because the resistance passed through the 

 vanishing point, the meniscus in the tube of the thermometer passed 

 the cross thread; this phenomenon was certain up to 1 mm. Hg: 

 ''Kahlhamn' lead, atomic weight 207,20 and uranium, lead [Ra G), 

 atomic loeight 206,06 have the same vanishinci point temperature within 

 the accuracy of^/^o degree. The same result was yielded by Pè-1919-ö; 

 an infiuence of the smaller current density in consequence of the 

 larger diameter could not be detected (the strength of the measuring 

 current was always 7,8 m.A.). 



§ 6. Resistances above the temperature of the vanishing point. 



The results of these measurements are given in fig. 2; the point 

 most to the riglit, placed within a square, is the result of a mea- 

 surement in liquid hydrogen. As vanishing point 7°, 2 K was taken. 

 To make the curve join on properly to the one in the field of liquid 

 hydrogen it must be traced as in the diagram ; that is why corres- 

 pondence with the points marked is defective. The broken crosses 

 have the following meaning: if the difference between the vanishing 



