CHEMISTRY: T. W. RICHARDS 
411 
THE COMPRESSIBILITIES OF THE ELEMENTS AND THEIR 
RELATIONS TO OTHER PROPERTIES 
By T. W. Richards 
WOLCOTT GIBBS MEMORIAL LABORATORY. HARVARD UNIVERSITY 
Presented to the Academy, May 22, 1915 
Eight years ago the compressibihties of thirty-five elements were de- 
termined at Harvard, in order to discover the relation of these compres- 
sibilities to one another and to other properties of these fundamental 
substances. All the values were referred to that of mercury, with the 
understanding that, although the compressibihty of mercury was not 
at that time very well known, they could all be easily corrected to the 
true standard when more complete knowledge of this quantity had 
been attained. 
This time now seems to have come. The recent research of Bridgman 
at high pressures and that of the author in conjunction with E. P. Bart- 
lett at lower pressures have furnished such a consistent and convincing 
outcome that the compressibility of mercury is no longer in serious 
doubt. Accordingly, it is appropriate that the older results should be 
corrected to the true standard. Moreover, a better standard of pres- 
sure is now available, and the pressure gauges used in the early vs^ork 
have been very carefully compared with it, so that the older results 
can be corrected in this respect also. 
The table below contains the corrected values of the compressibilities 
in question, together with new values for tungsten and tantalum, de- 
termined with the help of E. P. Bartlett, and of boron, determined 
with the help of J. H. Hodges. 
The megabar (or megabarie) is chosen as the measure of pressure be- 
cause this absolute unit bids fair to become the scientific standard of the 
future, being the pressure of one megadyne per square centimeter. It 
is almost 2% greater than the kilogram per square centimeter, and 1.3% 
less than the 'atmosphere.' 
In addition to the compressibihties, the table records also several 
other properties, which will be shown to be more or less related. Many 
of these also have been determined at Harvard, but some are due to the 
work of others. Most of these latter are easily found in the literature; 
complete references would occupy far too much space for the present 
pubHcation. 
