Two new compounds, (\mathrm{La}{2} \mathrm{~W}{3} \mathrm{O}{12}) and (\mathrm{LaFeW}{3} \mathrm{O}{12}), were prepared from (\mathrm{La}{2} \mathrm{O}{3}) and (\mathrm{WO}{3}) or from (\mathrm{Fe}{2} \mathrm{O}{3}, \mathrm{La}{2} \mathrm{O}{3}), and (\mathrm{WO}{3}). (\mathrm{La}{2} \mathrm{~W}{3} \mathrm{O}{12}) has a structure which can be considered as a distorted superstructure of the scheelite structure (\mathrm{CaWO}{4}) in which (1 / 3) of the Ca sites are vacant. It is monoclinic, with space group (\mathrm{C} 2 / \mathrm{c}) and (a=7.873) (2) (\AA, b=11.841) (2) (\AA, c=11.654) (2) (\AA), and (\beta=) (109.25(3)^{\circ}). LaIcW (\mathrm{O}{3} \mathrm{O}{12}) is triclinic with (a=7.569(3)) &, (b=) 7.537(2) (\AA, c=32.41(2) \AA, \alpha=90.13(4)^{\circ}, \beta=94.75(3)^{\circ}), and (\gamma=) (98.90(3)^{\circ}), and the structure consists of two distinct layers, one of which is a La tungstate which consists of a sheet of La in eight coordination and a sheet of (\mathrm{WO}{4}) tetrahedra and another which consists of a sheet of edge-sharing (\mathrm{FeO}{6}) octahedra sandwiched between two sheets of edge-connected (\mathrm{WO}{6}) octahedra. The reactivity of these compounds with (\mathrm{H}{2}) was investigated by TGA. (\mathrm{La}{2} \mathrm{~W}{3} \mathrm{O}{12}) is reduced at (1100^{\circ} \mathrm{C}) to yield a mixture of (\mathrm{La}{2} \mathrm{O}{3}) and (\mathrm{W}) metal. The products of the reduction of (\mathrm{LaFeW}{3} \mathrm{O}{12}) were found to depend on the composition of the atmosphere. In (\mathrm{N}{2}) with (5 % \mathrm{H}{2}) the compound yields a complex mixture of (\mathrm{La}{x}\left(\mathrm{WO}{3}\right){y}), compounds with (W) and a W-Fe alloy, while in (100 % \mathrm{H}{2}, \mathrm{La}{2} \mathrm{O}{3}, \mathrm{~W}), and the alloys (\mathrm{Fe}{6} \mathrm{~W}{7}) or (\mathrm{Fe}_{2} \mathrm{~W}) are formed. 1994 Academic Press, inc.