fi25 



§ 4. The Curie constant of ijndoliaiuvi .•<uliihntf. Iii ^ 3c il lias 

 been lueiitioiied already lluit fur ör/ Il 2,030, < 10~^ has lieeii fouiul. 

 Foi' llie Curie constant of Gd I we find : 



2'= 20^81 K. / == 1,0566 . 10 3 6'= 2,146 . 10-2 



7'= 14°,68 x = i-4663 „ 6'= 2,152 



tnean: 2,149 



Tlie iiieasuremeiits on (rd 1 have heen (considered as less accnrate 

 than liiose on (ril II, because (cf. ^ 3/ on the difficulties of the 

 adjustment) the tnbe appeared afterwards for unknown reasons to be 

 no! exactly in the nnddle between the pole faces, but 1,6 initi out 

 of the center. A previous determiVialion nf ihe Cniie-constant of 

 (Jil I quite inde|)endent of llie present researcli had given 2,113 X 10""^. 

 So it is not very probMl)ie that the large ditfereiu-e lietween the 

 Curie constants of (hi I and Gd 11 is due to inaccni'ale adjustment 

 of the tube only. Besides it must be remarked that different observers 

 have found \alnes differing more siill tlian the valnes mentioned: 

 from the results of Mile Feytis '), Kamkkmnüh Onnics and Pkkuikh '), 

 and Kamerlingh Onnes and Oostkrhi is ') the Curie-constant of gado- 

 linium sulphate is found to be *). 



Mile Feytis 2,167 .10-2 



K. O.andP. 2,086 



K. 0. and 0. 2,016. 

 These differences are not yet explained. 



Finally, I wish to expiess my sincere thanks to Professor Kamer- 

 LiNGH Onnes for his kind interest in my work. 



1) Paris C. R. 15.3 1911), p. 668. 



2) These Proceedings 14, p. 115; Leiden Comm. N '. 122a. 

 3| , , 15, p. 3^2; Leiden Comm. N». 129b. 



^) k correction lias been applied for the diamagiietism nf tlie crystal water and 

 of the anion. The first correction had been applied already by Mile b^EYTis. 



41 



Proceedings FJoyal Acad. Amsterdam. Vol. XXVL 



