EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 



109 



Copper. Two specimens were made for the radial flow method, and 

 four for the longitudinal. As in the case of iron, the thermo-couples 

 and heating element of the radial flow specimens were placed in 

 copper tubes sweated into place, and the results were not at all satis- 

 factory. The points were not regular, and the irregularities repeated, 

 showing some real effect. Furthermore, the two radial flow specimens 

 were made from contiguous lengths from the same piece of commercial 

 drawn rod, and the irregularities were much the same in character for 

 each specimen, showing a real effect of inhomogeneities in the metal. 



The four longitudinal specimens were made from electrolytic copper 

 wdiich I obtained a number of years ago from the Bureau of Standards. 



3 4 5 6 7 8 



Pressure. Kg. / Cm/ X 10' 

 Copper 



Figure 7. Copper. Thermal conductivitj^ on an arbitrary scale against 

 pressure in thousands of kg/cm-. Results obtained with a longitudinal flow 

 specimen. 



Their analysis is as follows : Cu 99.995 per cent, trace S, no x\g, CU2O, 

 As, or Sb. It is to be noticed that the purity is unusually high. 



Measurements were made on some of these samples in the annealed 

 condition, and others not; there seemed to be no difference in the 

 results. 



These four samples gave fairly good results, the points lying on 

 discrete lines, as usual. The least scattering of these is reproduced 

 in Figure 7. The effect is seen to be fairly large, and negative, the 

 mean effects shown by the four samples were —9.7, —8.2, —8.3, and 

 — 7.5% change respectively under 12000 kg/cm^. The mean is 

 —8.4%, but we will take as the best result —9.0% instead, because 



