Abstract: Method of casting an integral slide gate and nozzle assembly wherein a casing (11) conforming to the exterior sides and bottom of the valve is placed upside down on a flat smooth plate (12), a tube (14) is placed within the mold so formed to produce a channel in the cast valve, a first castable refractory exhibiting good resistance to molten metal is cast in the bottom of the mold, a tube (19) is placed about the passage-forming tube (14), the same first refractory castable is cast between the two tubes, and a refractory of lesser resistance to molten metal is cast within the remainder of the mold, the second tube (19) being removed after the casting is complete. Preferably casting is carried out while vibration is applied to the mold, the vibration continuing until after removal of the second tube (19). The second refractory can be an insulating material. Preferably the first castable is a high alumina material, for example one containing over 70%, most preferably over 90%, Al.sub.2 O.sub.3.

Abstract: A high purity periclase grain having less than 8 volume % porosity, less than 2% SiO.sub.2, and a CaO:SiO.sub.2 weight ratio not over 1.0 is produced in a single fire process by mixing from 0.5 to 1.5% finely divided SiO.sub.2 with a magnesium hydroxide containing (on the ignited basis) at least 98% MgO, not over 1.5% CaO, and not over 1.0% SiO.sub.2, drying the admixture, compacting it at a pressure of at least 10 tons/in.sup.2 (1400 kg/cm.sup.2), and firing the compacts at a temperature of at least 1700.degree. C.