The Force-Temperature Coefficient at Constant Elongation

The derivative occurring on the left of Eq. (20) may be expanded in terms of the independent variables T, P, and L as follows  

In order to arrive at Eq. (20), it is required to show that this quantity A is negligible. 

Since a — L/La where Lo is a function of pressure and temperature only. 

Introducing this expression along with Eqs. (A-3) and (A-4) into Eq. (A-2), we have 

For reasons which appear below, it is preferable to express this relation as follows 

---

No thermoelastic inversion should appear in the force-temperature coefficient at constant elongation a, inasmuch as the effect of ordinary thermal expansion is eliminated by fixing a instead of the length L as the temperature is varied. As the elongation approaches unity, both the force and its temperature coeffi.cient df/dT)p,a must van-... 

---