( 558 ) 



Ihi-,i;p \oliiino at 20" (\ it wcm-o rcdiirod to a pressui'o of 1 alm., 

 and it had followed tlio laws of tlio ideal gases. We then lind the 

 theoi-etieal normal \olunie fat 0° (A) l)v means of the eoeflieient of 

 pi'cssnre variation (= coefHieient of dilatation^ for the ideal iraseons 

 state. As the calenlations of the eorreetion that aecordiiiii: to C'omm. 

 N". 71 (These Proc. IV June 29. 1901. p 125) mnst he applied to 

 the coeflfk'ient of pressnre \ariation of pni-e hydrogen in ordei' to find 

 that coefTicient for the ideal gaseons state were not tinished when 1 

 Itegan my calenlations, I have adopted foi- this the valne 0.0030625, 

 which in Comni. N". 71 was given as a lii'st a]>proximation. The 

 eorrections, howexer, which accordingly must he applied to the 

 i-esnlts, will certainly lie far below the degree of accniacy which 1 

 conld attain in my experiments of the isothermals at high pressures. 



After what has heen said on the calibrations^), the measurement of 

 the normal volume and the reduction to the theoretical noinial volume 

 1 can ('online myself to a short note on the measurement of the 

 volumes. The top and the base of the mercury were read with an 

 eye-glass, parallax was avoided in the way described before (Comp. 

 this Comm, T j». 53:3). In this manner 0.1 mm. could be read. We 

 assumed that the mercury meniscus in the graduated stem of the 

 experimental tube has the form of a spherical segment, lience by 

 niulli]tlication of the bore by half the height the volume may be 

 found with a sufticient degree of accui-acy. our method of I'eading 

 coJisidered. When the mixtures split into two phases, the jwsition 

 of the li(|uid meniscus was also read. Corrections were applied for 

 I he expansion of glass due to heat and to the inner pressui-e. 



§ 4. ^'/n' iiicrtsureiDi'Ht of tin' jiri'ssiuws. The j)ressures were 

 measured with a hydroueu manometer, ranging from 62 to 196 

 atmospheres '). 



In the tirst part of this Comm. [\). 532 tf.; I lia\e discussed the 

 calibration, in § 3 of this paper the determination of the normal 

 \olume. We need only add that the hydrogen was )»repared as 

 described in Comm. X". 27 ZittingsNcrsl. \'. Mei 1.S96 p. 42. 



From the means of ilie values of T.i and T/, of the table 

 from which table \Tl forms an extract and tVom the normal Nolume 



1) Comp. this Comm. I, p. 53i2. 



-) It appeared that the manipulations of tlie stems of tlie manometer- and tlit- 

 piezometer lubes in the hfow-pipe, as for instance the sealing of the top of the 

 latter, had to be made vvilh si)ecial care and the tube had to be cooled very cai'e- 

 fully and slowly, else tensions will rise in the glass and conseijuently when liiirh 

 pressure is applied (in these experiments 1 'i-O aim. was readied, the manometer 

 has stood 195 atms. several limes) the lube will burst. 



