449 
and quantity of adsorbed fluid (¢ being the quantity of gr. of water, 
absorbed by 1 gr. of dry powder). 
——_—_——— ee ee 
QUARTZ 3 ANORTHITE 
Pip, | ix<10? Pip, | id 102 
0 0 jot | , 
0.020 | 0.29 00208 | 110 
0.048 | 0.31 0.048 | 1.85 
Or122) 4}; 0.33 O13 U.Sa 
0.306 | 0.34 0.306 | 1.88 
0.525 | 0.39 0.525 | 1.89 
0.718 | 0.40 Orte ol 
0.857 | 0.41 0.857 | 1.99 
0.915 | 0.42 0.915 | 2.04 
0.965 | 0.61 0.965 | 2.53 
By graphical representation the following curves were obtained : 
PlPo anorthite 
ipo quartz 1.00 
i 
0.005 0.010 
Both curves begin with a more or less horizontal part, then have 
the convexity below, with larger 7 first have a flexible point, then 
have the concavity below; they therefore have the shape of an 58. 
Thermodynamical relation between vapourtension and potential 
of molecular attraction. 
Prof. vAN per WaAats now called my attention to the fact, that 
in the following manner an approximate theory of the shape of this 
30 
Proceedings Royal Acad. Amsterdam, Vol. XV. 
