The determination of fluorine in rare earth fluorides by high temperature hydrolysis

The technique of pyrohydrolysis has been applied to the determination of fluorine in the fluorides of scandium, yttrium, and the lanthanons. These fluorides have been divided into two classes according to their rate of hydrolysis. Lutetium, ytterbium, cerium(III), scandium, gadolinium, terbium, dysprosium, holmium, erbium, and thulium florides can be hydrolyzed in 30 min or less. Yttrium, lanthanum, praseodymium, neodymium, samarium, and europium fluorides require from 45 to 150 min for complete hydrolysis. Accelerators, such as uranium oxide (U₃O₈), chromium(III) oxide, and a mixture of these oxides have been used successfully to reduce the tune required for quantitative hydrolysis of the fluorides in the latter group. The use of the correct accelerator reduces the hydrolysis time to 30 min or less for all these fluorides except lanthanum, praseodymium and neodymium.