484 



Physics. — " 77(t' specifi-c Ihcitl (it lom ti'iupi-rdtiny.-i.W. Mi'd.iwements 

 oil the specific heni of copper heticeen 14 and 9(^' K." Bj 

 W. H. Kkesom and H. Kamkkmngh Onnks. Communication 

 N°. 147r/ tVoui tlie Piiysicul Laboratory at Leiden. (Commu- 

 nicaled by Prof. H. KAMKRUNCin Onnes). 



iGümmunicatei-l in the meeting of June 26, Uilö). 



\ 1. Ill Comm. NM43 (Oct. 1914, Tliese Proceedings Dec. 1914) 

 § 6 we publisiied a series of measurements on the specific heat of 

 copper between 15 and 22° K. We iiave since made some improve- 

 ments in tlie experimental arrangement, particularij as regards the 

 resistance measurement for the purpose of the deterniinalion of the 

 temperature increase in the calorimetric experiment. Tiie determination 

 of the "sensitivity" of the TnoMSON-bridge arrangement (cf. Comm. 

 N°. 143 § 2) was made this time by shunting the standard resistance 

 of 1 fi (cf. Comm. N°. 143 Fig. 5) by a known resistance and 

 reading the resulting galvanometer deflection. Irregularities as men- 

 tioned in Comm. N°. 143. § 4 note 1 did not occur now. 



At a new calibration of the thermometer wire Aiirw it appeared 

 not to have remained so constant, especially at liquid hydrogen 

 temperatures, as at the time of the measurements of Comm. N°. 143 

 we concluded from determinations in liquid hydrogen on two different 

 days (table I Comm. N". 143j, and also from the comparison of the 

 result of a control measurement') at the boiling point of oxygen on 

 May 25 with the results of the measurements of May 18 1914. See 

 table I. 



Hence the resistance of the gold wire Au,.-i ''), which is enclosed 

 in enamel between metal, ap[)ears to siiow small differences when 

 brought to the same temperature at different times. This behaviour 

 agrees with what has been experienced with wires sealed in glass: 

 cf. Kamerlingh Onnes and Holst, Comm. N°. 141rt § 4. 



At liquid oxygen temperatures the differences are, however, so 

 small, that for the calorimetric determination at these temperatures, 

 they are unimportant. At liquid hydrogen temperatures account has 

 to be taken of these changes. 



1) Tills control measurement, wliicli was not mentioned in Comm. N". 143, gave : 



May 25 '14 90.45 3.6616 



-) The preliminary treatment consisted in (cf. Comm. N". 143 § 3 : glowing 

 before the winding, then 6 times cooling in liquid air and allowing it to return 

 to room temperature, likewise "1 times in liquid hydrogen. 



