aluminium in solid liquid Br2 was dropped into a solid mixt. of oxide and a large excess ofAl powder in one-end sealed quartz tube under Ar atm., evacuated, seale d, placed in a tabular furnace with temp. gradient from 750 to 460 K;

in benzene (vac.); soln. of Pr compd. and BrCH2CH2Br was heated at 120°C for 5 h; formed ppt. of PrBr3 was filtered off; org. layer was sepd. by distn.;

aluminium in solid byproducts: O2; Pr6O11, AlBr3 (Ln:Al = 1:4) and Al powder were placed into an one-end sealed quartz tube under Ar, sealed under vac., heated at 600 K for 1 h; sealed tube was placed in a tubular furnace with a reduced temp. gradient from 750 to 460 K, vapor transport reaction for 6 h, tube was quicklyremoved from the furnace, the hot end was quenched with water, AlBr3 wa s condensed;

NH4Br in hydrogen bromide HBr (liquid); Pr6O11 dissolbed in hot HBr, crystd., dehydrated in the presence of NH4Br; melted, distilled (vac.) at 1150 K, elem. anal.;

Pr-oxide in not given according to A. Brukl, Angew. Chem. 52 (1939) 152, G. Meyer, P. Ax, Mater. Res. Bull. 17 (1982) 1447; vac. distn. in Ta container;

in not given G. Meyer, P. Ax, Mater. Res. Bull. 1982, 17, 1447-1455; vac. distillation at 900°C;

in water Pr6O11 dissolved in aq. HBr by heating in a Teflon beaker in sand bath; NH4Br added; evapn. to dryness; ground in agate mortar; heated slowly t o 170°C in N2 flow; further heated under vac. to 450°C; purified by sublimation at 800°C below 1E-6 mbar;

byproducts: CO2, C; 4-fold excess of CBr4; 400-600°C, 4-5 h; further by-product: Pr oxide bromide;

HBr vapor, at higher temp.;