o^8 



Physics. — ''Mea.'<ar(')nenU on the rapiUdrlti/ of Uqiilil hi/(lrogen^\ 

 By H. Kameklingh Onnes aiid H. A. Kuypers. (Communication 

 N°. 14:2(1 from the physical laboratory at I.eyden). 



(Communicated in the meeting of June 27, 1914). 



For the determination of the capillary constant of liqnid hydrogen 

 in contact with its saturated vapour the method of capillary rise was 

 used. The apparatus are in the main arranged in the manner as used 

 for other liqnid gases in Comm. N". 18. On plate I A of Comm. 

 N°. 107 a may be seen that pai't of the apparatus 

 which serves to condense the gas in the wide 

 experimental tube (fig. 1), inside which is the capil- 

 lary ; for this purpose the tube of fig. 1 is sealed 

 in at (/j. 



The radii of the sections of the tubes were found 

 y » by calibi-ation with mercury as follows : 



Y 1 radius of Ihe capillary inside?' =0.3316 cm 



„ ,, ,, outside )\ = Ü.080J cm 



„ ,, ,, surrounding tube inside /i= 0.554 cm 



--> 



&> 



Jfeaswwnenf of the ra pillar y rise. The reading 

 of the ascension gave some trouble as it had to be 

 made through a numl>er of glass vessels and baths. 

 The rise was measui-ed with a cathetometer ; to test 

 I J the accuiacy of the readings they were taken one 



xy time on a millimctrescale which had been etched 



Fig. 1. on the capillary and another time directly on the 



scale of tiie cathetometer. When it was found, that there was no 

 difference between the heights obtained in the two ways, they were 

 afterwards only measured by means of the scale of the catheto- 

 meter, because, when the cryoslat was filled with the different licpiid 

 gases, the divisions on the capillary were difficult to distinguish owing 

 to the rising gas-bubbles in the liquids. 



Temperature. The temperature was deduced from the pressure of 

 the vapour in the hydrogen-bath using the vapour-pressure curve 

 (H. Kamerungh Onnes and W. H. Keesom, Comm. N°. 137 J. table 

 on page 41). 



Ohs'en)afHms\ The heiglits measured and the corresponding tem- 

 peratures of the hydrogen are contained in the following table. 



