10 
PHYSICS: P. W. BRIDGMAN 
THE RESISTANCE OF METALS UNDER PRESSURE 
By P. W. Bridgman 
JEFFERSON PHYSICAL LABORATORY, HARVARD UNIVERSITY 
Communicated by E. H. Hall, November 27, 1916 
In this note are summarized many of the most important results of 
an extended series of measurements on the resistance of metals under 
hydrostatic pressure. A more detailed account of the experiments 
has been offered for publication in the Proceedings of the American Acad- 
emy of Arts and Sciences. The pressure range of this work is from 0 
to 12,000 kg., and the temperature range from 0° to 100°C. The most 
extensive previous measurements have been made by Lisell and Beck- 
man, ^ who made all their measurements at 0° over a pressure range of 
3,000 kg. 
This investigation includes 22 metals, embracing nearly all the com- 
mon metals obtainable in the form of wire. Special precautions were 
taken in most cases to insure the greatest possible purity; the tempera- 
ture coefficient of resistance at atmospheric pressure affords an indica- 
tion of the probable purity. Of the metals above, Sn, Cd, and Zn 
were Kahlbaum's ^K' grade, Tl and Bi were prepared by electrolysis 
and were of high purity, Pb, Ag, Au, Cu, Fe, and Pt were of exceptional 
purity, and the others are probably not better than of high commer- 
cial purity except Al, which was much better than ordinary. 
The results are summarized in the table. Two kinds of pressure 
coefficient are listed: 'instantaneous coefficient' and 'average coefficient'. 
The 'instantaneous coefficient' is the value of the derivative - 
where w is the observed resistance at the pressure and temperature in 
question. The 'average coefficient' between 0 and 12,000 kg. is the 
total change of resistance between 0 and 12,000 kg. divided by 12,000 
and by the resistance at atmospheric pressure at the temperature in 
question. 
The effect of pressure is to decrease the resistance of all metals ex- 
cept Bi and Sb, the resistance of which suffers a comparatively large 
increase. The anomalous behavior of Bi was known before, but that of 
Sb is new. The Sb was used in the form of extruded wires. The magni- 
tude of the effect for normal metals varies from 12% to 0.8% for 10,000 
kg., but Te forms a notable exception. 
It is apparent from the table that the relative change of pressure 
coefficient with temperature is much less than the relative change of 
