The Pippard relations have been reformulated in terms of the spectroscopic parameters and applied to the NH4Cl system in the vicinity of its lambda-transition. We have effectively tested some of these relations in an earlier study where we have used, for the frequency shift, data for the nu5 lattice mode of NH4Cl. Here, using our observed frequency shifts for the internal mode, nu2 of NH4+, we have obtained a good fit to the Pippard relations for temperatures below T(lambda) for the NH4Cl system. We have then been able to extract the frequency shift data for the nu2 internal mode as a function of temperature, using the specific heat and also thermal expansion data from the literature. The method of analysis for obtaining the thermodynamic data from the spectroscopically measured quantities or vice versa is given here.