5fVjit CONTENTS. 



Physics. W. H. Keesom : "On tlie equation of state of an ideal monatomic gas accof- 

 ding to the quantum-theory". 227. 



W. H. Keesom : "On the theory of free electrons in metals". 236. 



H. Kamerlingh Onnes and C. A. Crommelin : "Isothermals of di-atomic 



substances and their binary mixtures. XIII. Liquid densities of hydrogen between 

 the boiling point and the triple point; contraction of hydrogen on freezing"". 245. 



— W. H. Julius : ''On the interpretation of photospheric phenomena". 264. 



— P. Martin: "The magneto-optic KERR-eilect in ferro magnetic compounds". IV". 318. 



— J. P. KuENEN and S, VV. Visser: "The virial coell'icient B for normal butane". 350. 



— J. P. KuENEN and S. W. Visser : "The viscosity of the vapour of norma 

 butane". 355. 



— F. E. C. Scheffer : "On the system hexane-water". 404. 



— E. OosTERHUis : "Magnetic researches. IX. The deviations from Curie's law in 

 connection with the zero-point energy". 432. 



— H. Kamerlingh Onnes and W. H. Keesom: "The vapour pressures of hydrogen 

 from the boiling point down to near the triple point". 440. 



— S. Weber: "Vapour-pressures at very low reduced temperatures. II. The vapour 

 pressure of carbon dioxide in the range from — 140° (J. to about 160° C." 445. 



— W. H. Keesom : "On the magnetization of ferro magnetic substances considered 

 in connection with the assumption of a zero-point energy". 454. II. 468. 



— C. A. Crommelin : "Isothermals of monatomic substances and their binary 

 mixtures. XV. The vapour pressure of solid and liquid argon, from the critical 

 point down to — 206° C." 477. 



— J. K. A. "Vy^ERTHEiM Salomonson : "Contribution to the knowledge of the string 

 galvanometer". 522. 



— W. J. H. Moll: "A rapid thermopile". 568. 



— P. Ehrenfest : "A mechanical theorem of Boltzmann and its relation to the 

 theory of energy quanta". 591. 



— W. H. Keesom: "On the question whether at tlie absolute zero entropy changes 

 on mixing". 669. 



— H. Kamerlingh Onnes and Albert Perrier : "Magnetic Researches. X. Appa- 

 ratus for the general cryomagnetic investigation of substances of small suscepti- 

 bility." 689. 786. 



— Ph. Kohnstamm and K. VV. Walstra : "An apparatus for the determination of 

 gas isotherms up to about 3000 atni." 754. 822. 



— .1. J. VAN Laar : "A new relation between the critical quantities and on the 

 unity of all the substances in their tliermic behaviour". 808. 924. 1047. 



~ J. D. VAN DER Waals : "The volume of molecules and tlic volume of the 

 component atoms". 880. 



— E. OosTERiiuis : "Magnetic researches. XL Modification in the cryomagnetic 

 apparatus of Kamerlingh Onnes and Perrier." 892. 



— Albert Perrier and H. Kamerlingh Onnes: "Magnetic researches. XII. The 

 susceptibility of solid oxygen in two forms". 894. XIII. The susceptibility of liquid 



