| 摘要 |
A monohydrate of barium or strontium hydroxide is made by evaporating an unsaturated solution of the hydroxide until there is obtained a constant boiling point slurry of the monohydrate crystals suspended in a saturated solution of hydroxide mother liquor and recovering the crystals. The initial solution may contain less than 58.8% wt. of BaO (i.e. it has a hydrate number greater than 5) and boiling may be continued until the saturated Ba(OH)2 liquor has an equivalent hydrate number of 4.5 to 5.0. Boiling may be discontinued when the solids content of the Ba(OH)2 slurry is 15-50% wt. Alternatively, water may be flashed out of the saturated Ba(OH)2 solution, the super-saturated solution then being fed to a crystallizing chamber containing seed crystals of Ba(OH)2H2O, where further crystals are grown in situ. The crystals may be removed by a heated centrifuge or filter and then cooled in an inert atmosphere. The mother liquor may be recycled if desired. The evaporation may be performed under increased pressure, e.g. 1.68 or 2.5 atm., until a saturated solution of equivalent hydrate number of 3.8 or 2 respectively is obtained, the pressure is then released, e.g. by a spray nozzle, to form Ba(OH)2.H2O. The evaporation may be also performed under reduced pressure. The invention can be used to prepare mixtures of Ba and Sr hydroxide monohydrates or as a means of separating them from each other. The Ba(OH)2.H2O. produced may have a monoclinic biaxial positive crystalline structure and a bulk density of at least 90 lbs./cub. ft. At least 90% wt. of the particles can be -20 to +100 Tyler mesh with less than 1.5% wt. being -200 mesh. The refractive indices of the monohydrate may be 1.594 along the a -axis, 1.620 along the b -axis, and 1.648 along the g -axis. The crystals may have a diameter of 0.2 to 1.5 mm. |
