CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL 

 LABORATORY, HARVARD UNIVERSITY. 



THE TECHNIQUE OF HIGH PRESSURE EXPERIMENTING. 

 By P. W. Bridgman. 

 Presented, Jan. 14, 1914. Received, Dec. 29, 1913. 



In this paper I propose to collect the results of several years' 

 experience in designing apparatus and conducting experiments at 

 high pressures. The rather unusual magnitude of the pressures, 

 from 12000 to 30000 kgm / cm-, has made necessary the development 

 of methods different from those which have hitherto sufficed for more 

 moderate pressures, up to perhaps 3000 kgm/cnr. I shall endeavor 

 to present enough of the details of manipulation so that any one may 

 construct apparatus for experimenting in this as yet almost untouched 

 field of higher pressures. It is not claimed that the methods presented 

 furnish the only solution of the problems of high pressure technique; 

 all that is claimed is that the methods given are possible solutions 

 which have stood the test of constant use for a number of years. 



The plan of presentation is to indicate the essential parts of a piece 

 of high pressure apparatus, and then to describe in detail the peculiar 

 features of construction of each of the parts. 



The apparatus consists essentially of a chamber in which pressure is 

 produced by a plunger, a mechanism for pushing the plunger into the 

 chamber, a tube connecting the chamber in which pressure is produced 

 with a second chamber adapted to the particular investigation, and a 

 pressure gauge. The second chamber is the only part of the appara- 

 tus that need be varied for different experiments. The other parts 

 will be described in detail here. 



Packing. 



Obviously an absolute essential to the success of any high pres- 

 sure apparatus is some reliable method of packing. I shall describe 

 here the broad principle of this packing, leaving for further de- 

 scription the numerous modifications for special uses. All the packing 

 used in this work is so designed that at high pressures it is made 

 tighter by the action of the pressure itself. Figure 1, showing the 



