( 760 ) 



§ 5. The hydrogen. 



The filling was accomplished for Series III with all the improve- 

 ments described in Comm. N u . 94 e § 2. For the first series the 

 purification by means of cooling - in liquid air was not yet applied, 

 in the second series it was, but without application of high pressure. 



§ 6. The temperatures. 



The temperatures t i and t 3 respectively of the divided stem b± and 

 the steel capillary // L (see Comm. N°. 69 PL II) were determined 

 in the same way as in Comm. N°. 78 § 13. In series I three ther- 

 mometers were placed along the steel capillary, and one at the part 

 of the glass capillary ƒ„ that remained outside the cryostat. The 

 refrigerating action of the cryostat proving to be very slight even 

 in the immediate neighbourhood, only three thermometers were used 

 in the following two series, two at the ends and one in the middle 

 of the steel capillary. The influence of an error of 1°C. in the 

 temperature of the capillary (comp. Comm. N°. 78 § 13) is only 



1 1 



- of the total compressed volume at — 100° 'and at — 200 \ 



4000 l ' 10000 



For the temperature of the glass capillary we assumed here that 

 indicated by the thermometer at the end of the steel capillary. 

 This simplification is the more admissible as the temperature in 

 the cryostat is lower, and hence the volumes outside it contain less gas. 

 The temperature of the glass capillary in the cryostat has been 

 determined in the same way as was followed in the investigations 

 with the hydrogen thermometer mentioned in Comm. N°. 95 ,; . As the 

 arrangement of the cryostat was the same in the two cases, and the 

 measuring-apparatus placed in it had almost the same form, there 

 was no objection to start from the previously found data for the 

 determination of the temperature of the capillary, (see Comm. N°. 95 e 

 §4). This method gives sufficient accuracy, as, reasoning in a similar 

 way to that followed in the said communication, we arrive at the 

 result, that an error of 50° in the temperature of the part of the stem 

 that is taken into consideration still gives a negligible error in the 



1 



final result, viz. less than . 



5000 



The temperature t 1 of the piezometer-reservoir was determined by 

 means of the resistance-thermometer, which (cf. Comm. N°. 95 c ) had 

 beforehand been compared with the hydrogen-thermometer. 



They differ little from those at which the calibration of the resistance- 

 thermometer took place. Hence the reductions are simple and maj r 

 be effected with great accuracy. 



The temperatures were not calculated directly from the resistance 



