Abstract: A process for producing aluminum fluoride particles having a smooth surface, comprising the steps of adding aluminum fluoride seed crystals to a super-saturated solution of aluminium fluoride; allowing aluminum fluoride particles to be precipitated under heating and agitation; collecting the aluminium fluoride particles by filtration; and drying them, wherein: a super-saturated solution of aluminium fluoride containing 0.6 to 1.3 wt % of fluosilicic acid which is preferably obtained by reacting aluminum hydroxide with fluosilicic acid in an [Al(OH).sub.3 /H.sub.2 SiF.sub.6 ] molar ratio of 1.80 to 1.90 is used as the crystallization mother liquor.

Abstract: A method of manufacturing aluminum fluoride anhydride by means of a wet method. This method is featured in that a seed crystal of AlF.sub.3.3H.sub.2 O containing not more than 5% of fine particle 40 .mu.m or less in diameter is added into the super-saturated solution of aluminum fluoride in such a ratio that the total surface area of the seed crystal is in the range of 40-100 m.sup.2 per 1 kg of AlF.sub.3.3H.sub.2 O to be precipitated until an initial concentration of the super-saturated solution is reduced to 1.6%. The initial concentration of the super-saturated solution is adjusted to 8 to 15%. Resultant slurry is heated under agitation, thereby precipitating in batch-wise large AlF.sub.3.3H.sub.2 O particles which are then separated, dried and dehydrated.