Lithium hexafluorophosphate, isolated from hydrogen fluoride solution (anhydrous) by decanting and filtering, is an adduct of composition LiPF6*HF. By thermogravimetric investigations the dynamics of HF removal from LiPF6 by LiPF6*HF thermal decomposition was studied. Based on the experimental data the constants entering into the equations as C=C-0*exp(r*K-0*exp(-E/RT)) were calculated, explaining the thermal decomposition processes of LiPF6*HF and LiPF6.