atmosphere gas the slurry was filtered for 10 minutes in a flow of an atmosphere gas consisting of 3 mol of pf 5 and 97 mol of nitrogen at a flow rate of 15 l min dried in the same atmosphere gas at room temperature for 25 min and finally heated at 105 u00b0 c overnight for example about 6 to 8 hours the amount of the lithium hexafluorophosphate crystal yielded was 11 3 kg and impurities were 50 ppm in hf and 70 ppm in lif the amount of pf 5 used was 0 008 kg per 1 kg of lithium hexafluorophosphate hydrofluoric acid anhydride solution containing 22 lithium hexafluorophosphate was cooled at u2212 20 u00b0 c to deposit a crystalline form of lithium hexafluorophosphate next this slurry was transferred to the filtering apparatus 20 l liter volume with inlet and outlet orifices for the atmosphere gas the slurry was filtered for 10 minutes in the flowing atmosphere gas the atmosphere gas consisted exclusively of nitrogen and was fed at a flow rate of 15 l min the slurry was then dried in the atmosphere gas at room temperature for 25 min and finally heated at 105 u00b0 c overnight the amount of the lithium hexafluorophosphate crystal yielded was 11 1 kg and impurities were 58 ppm in hf and 930 ppm in lif the slurry decomposed during filtering and drying resulting in an increase in lif as an impurity hydrofluoric acid anhydride solution containing 22 of lithium hexafluorophosphate was cooled at u2212 20 u00b0 c to deposit a crystalline form of lithium hexafluorophosphate next this slurry was transferred to the filtering.