Fractional precipitation of the hydroxides by means of ammonia, alkalies, or alkaline earths has also been frequently employed. A modification of this process is the precipitation with aniline, carried out by Kruss;[358] in this method, the solution of the chloride in warm dilute alcohol is treated with an alcoholic solution of the organic base. Another modification is the ‘Oxide process’ employed by Auer von Welsbach[359] for the separation of the cerium elements, and by Drossbach[360] in the yttrium group. The concentrated solution of the mixed salts is thoroughly digested with the oxides obtained by precipitating a fraction of the earths; the more strongly basic oxides tend to displace the less basic, so that these accumulate in the insoluble part. The solution is filtered from the undissolved oxides, another fraction precipitated, and the oxides obtained from the precipitate digested with the concentrated solution as before. [358] _Zeitsch. anorg. Chem._ 1893, ~3~, 108, 353. [359] _Monats._ 1883, ~4~, 630. [360] _Ber._ 1902, ~35~, 2826. [Illustration: ~GROUP B~ YTTRIUM DOUBLE SUPLHATES. Fractionate as Bromates. ||||| +--------------------------+|||+-------------------------+ | +------------+|+------------+ | | | | | | ~1~ ~2~ ~3~ ~4~ ~5~ Gd, Tb, Dy. Tb, Dy, Ho, Dy, Ho, Er, Yt, Er, and Tm, Yb, Lu, Yt. Yt. Sc? etc. For separa- Transform to Fractionate Fractionate Continue. tion of Ethyl- by Nitrate by Nitrate ||||| Terbium sulphates. Fusion. Fusion. ||||| group.--+ ||| || || ||||| | | | | ||| +---+| || ||||| Terbium | ||| | | || ||||| Group. | ||| | | ||+----------+|||| +----+ ||| | |+-----------+|| +---+||| |+----------+|| | || +-----+| | ||+-----+ || +-----+| | || | | | |+-----+| ~6~ | ~8~ | ~10~ | ~12~ | ~14~ || Tb, Dy. | Ho, Yt. | Yt, Er. | ~Tm.~ | ~Lu.~ || Continue | Fractionate | Continue. | Bromate. | Bromate.|| Ethylsulphate| by Nitrate | | | || Fractiona- | Fusion. | | | +----+| tion. | | | | | | +---+ | | | | | | | ~7~ | ~9~ ~11~ ~13~ | | ~Dy.~ | ~Yt.~ ~Er.~ ~Yb.~ | | Ethylsulphate.| Nitrate. Nitrate.