1011 
on the particular properties of the substance of which the centre of 
‘attraction consists. 
The time of revolution 7’ (the time in which g increases by 22) 
can easily be calculated. It follows namely from (18) and (19) that 
; 2k 
dp = Ac*y (a+8 cos w)? {1 — — (4+ eos wi, 
Cc. 
and from this, accurate up to quantities of the second order of 
magnitude, 
dy 2k dw 
Ac*ydt = —_—_—_—— + — ————_. 
(a+B cosy)? cc a+Pcos wp 
From this it easily follows, that 
Wer 2n a 4 k 
if Verg? a? — B? ce) 
Let us call a half the major axis of the ellipse, then 
and we get 
k En rn k 
a Kr : Sata 
T depends therefore still exclusively on the major axis of the orbit; 
this is, however, not the case with the time of revolution in the 
ellipse. In the first member we may substitute 42°a*/c’ Tl tor hea 
and thus we get 
her ara le 7 k 
a = |: : en 
AET An? 
instead of the third law of KEPLER. 
Chemistry. — “On gas equilibria, and a test of Prof. J. D. vas 
DER Waats Jr.’s formula’. I. By Dr. F. B. C. SCHEFFER, 
(Communicated by Prof. J. D. van per WaaLs). 
(Communicated in the meeting of Dec. 30, 1914.) 
7. The equilibrium I, = 21. (Continued). 
In my preceding paper') I have shown that from the determi- 
nations of the iodine equilibrium the value 0.41 10-° em. follows 
for the radius of inertia of the iodine molecule; the iodine disso- 
ciation can therefore be represented by equation 8, when 2= 15u 
and log M = — 38.20 are there substituted. That this equation 
sufficiently represents the experimentally found values, appears from 
. 1) These Proc. 17, 695 (1914/15). 
Gi* 
