382 J. W. Gibbs — Vapor-Densities. 
pene was reduced by mixing the vapor with air. In Table 
ITI all these determinations are compared with the formula 
1... 3°6 (D—3°6) 5441 
Sy kee > bet 978 
The differences between the calculated and observed values are 
often large, in six cases exceeding ‘80; but they exhibit in 
general that irregularity which is characteristic of errors 0 
observation. We should expect large errors in the observed 
densities, on account of the difficulty of obtaining the substance 
in a state of purity, and because the large value of the density 
renders it very sensitive to the effect of impurities which 
diminish the density,—also because the specific heat of the 
vapor is great, as shown by the numerator of the fraction in 
the second member of (18),* and because the density varies 
very rapidly with the temperature as seen by the numbers in 
the third column of Table VIII. 
+ log p — 14°353, (13) 
t 
withstanding the abrupt change of pressure. Yet it is difficult 
unequivocal evidence. Now it is worthy of notice that the 
nea raniene meee 
i ose ANE itia — 
