A method of measuring linear expansivity at low temperatures
Measurements of linear expansivity can provide information concerning the behavior of metals. Data concerning the behavior of linear expansivity of metals at low temperatures, when combined with complementary data on specific heat and elastic constants, can disclose the enharmonic nature of interatomic forces. Close observation of the linear expansivity of a superconductor as it undergoes a transition from a superconducting phase to a normal phase at zero magnetic field may reveal the nature of this postulated second order phase transition. The data might specify which of two competing theories of second order phase transitions is correct in this case - Ehrenfest*s or Tisza's. That is, the data would indicate whether the discontinuity in linear expansivity is finite or infinite, respectively.