526 Mr. E. Buckingham on the Thermodynamic 
determined by two methods. The corresponding tension 
measurements were carried out by the drop-pipette method. 
3. The results show a considerable discrepancy between 
the actual amount adsorbed and that calculated on Gibbs's 
theory — the actual amount measured being always in excess 
to the extent of twenty to eighty times the theoretical values. 
4. Experiments with dye-stuffs show similar behaviour, 
the discrepancy being of the order stated. 
5. As regards the discrepancy noted, no suggestion is as 
yet offered. Further experiments are in progress employing 
other electrolytes and non-electrolytes as material for measure- 
ments of a similar nature. 
In conclusion, I would express my indebtedness to Professor 
onr 
work. 
Donnan for his advice and criticism during the course of this 
XL VIII, The Thermodynamic Corrections of the Nitrogen 
Scale. By Edgar Buckingham *. 
[Plates XV.-XVIL] 
Introduction. 
LET fjb denote the ratio of the cooling observed to the fall 
of pressure at the porous plug in the Joule-Thomson 
experiment. For small and moderate pressures, experiment 
shows that this ratio is nearly or quite independent of the 
fall of pressure and of the mean value of the pressure- 
Assume that the observed value represents the limiting value 
for an infinitesimal fall of pressure. Let p be expressed in 
centigrade degrees for a fall of pressure of 1 dyne/cm. 2 
Let Gp be the specific heat at constant pressure expressed 
in ergs. Let v be the specific volume of the gas. Let 
be the absolute thermodynamic temperature. Then the 
fundamental equation of the porous-plug experiment may be 
written : 
•®i- + ^ (1) 
This may easily be put into the form 
(p = 7r= const.) ... (2) 
* Communicated by the Author. 
60 ) a 
fiGpdO 
