OniCoherence and Recoherence. 165 
and therefore K ES K,, 
ex 
We found K,=K’ o%, therefore we get 
and according to the equation K= renee, there follows 
Rage th ER Ay /y 
(iyo Wa ae ) 
from which we derive 
Beale U/l“ 
Ja anny Os ak ae 
Since v,, the concentration of water is in diluted solutions 
nearly constant, we may contract the value K VK’. into one 
constant, and by squaring results Vw 
Yy on Cy 
(l—wy\v 
the equation of Rudolphi-van’t Hoff. 
Some of our assertions were only approximate, and there- 
fore that equation cannot have an exact validity. 
Finally, let us suppose that the nonelectrolytes and the 
weak electrolytes are not able to dissociate the double mole- 
cules of the solvent, and that therefore the equation 
(=u) te 
is not changed, then we can understand that in this case the 
equation : =K is the right expression for the facts. 
(l=) 
Charlottenburg-Berlin, Technische Hochschule. 
XVIII. On Coherence and Recoherence. 
‘By P. BopuewereA., D-Se., and C. A. B. Garrett*. 
J HEN electromagnetic waves fall on a loose contact 
of two metallic or other conducting surfaces, co- 
herence occurs between the surfaces whether there be a 
completed metallic circuit or not. The resistance of the con- 
tact falls, and the surfaces cling together and can only be 
* Communicated by the Physical Society : read May 27, 1904. 
