287 
Physics. — “On the Fundamental Values of the Quantities b and 
wa for Different Elements, in Connection with the Periodic 
System. HL. Discussion of the Different Groups of Elements 
Separately.” By Dr. J. J. van LAAR. (Communicated by Prof. 
H. A. Lorentz). 
(Communicated at the meeting of May 27, 1916). 
1. In the preceding Paper!) in § 3 we saw that hj, can be 
obtained from the (quid volume v, (at such a low temperature 
that the vapour density may be neglected) through the formula 
kn Xfi tf On Pe) 
‘ee. 
in which y represents the (reduced) coefficient of direction of the 
straight diameter between D, and PD, in a D,7-diagram, and im, 
is the reduced (absolute) temperature 7’: 7%. 
We might even continue to use this formula, when v, represents 
the volume in so/id state — when namely the law of the variability 
of v with 7’ does not deviate too much from that holding for the 
liquid state. But in case v, is only known for the solid state, we 
can also first reduce v, to the value of » at the triple point (by 
means of the experimentally determined formulae for the expansivity), 
and then apply the above formula (1) starting from that point. 
A great difficulty is experienced for elements the melting point 
of which lies very high, and for which the value of y is perfectly 
unknown; besides — when also that of v at the melting point is 
unknown --- the value of y can in many cases no longer be 
calculated from the empiric formulae of expansion in the solid state, 
seeing that mostly these are only valid for temperatures far below 
the melting point. In such cases there is often nothing left but to apply 
formula (1) as a first approximation also to the solid state, and 
determine the value of y from other data. In many eases the formula 
‘(valid for the liquid state) 
pe =a. 0,088 1 Fest on be oS, Ss en ee) 
can be used for it, which formula was lately derived by me’). It 
will be remembered that 2y is also — bj : h,, and therefore expresses 
the degree of the variability of 5. 
1) Denoted by I in what follows: cf. These Proc. of March 25, 1916. Paper 
I appeared in These Proc. of Jan. 29, 1916. 
Cf. also Journal de Chimie physique. T. 14, N°. 1 (March 31, 1916). 
2) Cf. the series of papers, cited by me already in | (Footnote 3) on p. 1221, 
particularly the 3°¢ paper of May 29, 1914, p. 1051. 
