“…A literature review showed that ammonium fluorides can be considered as the main reagents for processing chemically stable oxides and other oxygen-containing compounds. Well known is the use of a melt of ammonium fluorides as a reagent for processing the most chemically stable oxygen-containing compounds and also minerals (tantalite, 11 laterite, 12 monazite, 13 spodumene, 14 trinitite, 15,16 zircon, [17][18][19][20][21][22] ilmenite, 23 titanomagnetite, 24,25 polymetallic slags, 26 etc.) and pure oxides (plutonium dioxide, 27 thorium dioxide, 28 lanthanum, neodium and gadolinium, 29 etc.).…”