J. W. Gibbs — Vapor- Densities. 291 
increase with the pressures more rapidly than the formula 
allows; but the differences are not too large to be ascribed to 
errors of observation, and the experiment at the lowest pres- 
sure (8£"™) also shows a large excess of observed density. 
much more critical test may be found in the comparison 
of Naumann’s experiments with those of Deville and Troost, 
are compared with the densities calculated by the formula 
1589(D —1:589) 3800 
= — 12°641. 11 
loo 
of the third series of the Annales de Chimie et de Physique 
and the higher pressures employed at this peas cannot 
ith res 
pressure of saturated vapor is about 19™™ at 13°, 20°5™™ at 
15°, 33:57™ at 22°, and 585™ at 82°. By interpolation 
between the logarithms of these pressures, (in a single case, 
extrapolation), we obtain the following result. 
~ 
