Extremely accurate determinations of the linear thermal expansions have been made interferometrically from — 196°C to temperatures about +400°C for Al and +700°C for Fe, Ni, Cu and Au. The relationship between true thermal coefficient of expansion and temperature conforms very well to the Grueneisen-Debye theory when values are chosen for the Debye characteristic temperatures which turn out to agree well with those chosen to achieve agreement with the Debye theory of specific heats. Our values for these characteristic temperatures are: 410°K for Ni, 420°K for Fe, 400°K for Al, 325°K for Cu, and 190°K for Au. The magnetic Curie temperature for Ni is found to be 352°C. In plotting true coefficient of thermal expansion versus temperature Simon and Bergmann found a horizontal plateau at about 175° to 235°K for Ni and Fe; but we do not confirm this.

• Received 8 August 1941

DOI:https://doi.org/10.1103/PhysRev.60.597