EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 



101 



ever, were made on lead of unusually high purity provided by the 

 Bureau of Standards for the calibration of thermo-couples by the 

 melting point. The analysis of this lead was as follows: 



Ag .0002 - .0003%, Sb .0019 - .0028%, Sn .0008 - .001 l%o, 

 Cu .0003 - .0004%o, Fe. .0004 - .0006%, As, Bi, Zn, Co, Ni, trace, 

 Cd, Mn, none; Lead (by difference) 99.9948 + %. 



The melting point according to the certificate of the Bureau was 327°. 3. 

 The accidental errors in the measurements were greater than differ- 

 ences due to slight amount of impurity, since all varieties of metal 

 gave essentially the same results. The results are summarized in the 

 following table. 



TABLE I. 

 Summary of Results for Lead. 



Description of Specimen 



Solid Cu sheath, 3 copper tubes, commercial 



" « « « " " " test " 



" " " central Cu tube, " test " 



Split Cu sheath, central Ag tube, Bur. Stds 



Large cylinder, no sheath, central Ag tube. Bur. Stds 



<( » (( U (I U K fl U 



" 0.007" central hole. Bur. Stds. . 



a u a II u u a u u 



Longitudinal flow, Bur. Stds. holes cast in specimen 



u l( II a u u u u 



Average 



Percentage Change 



of Conductivity for 



12000 kg/cm'- 



20.7 



In the above table, those specimens for which the nature of the 

 central tube only is specified had the thermo-couple holes cast in the 

 body of the metal in the isthmus shape already described. The 



