公开(公告)号：US3920802A

公开(公告)日：1975-11-18

申请号：US44794874

申请日：1974-03-04

Applicant: KEWANEE OIL CO

Inventor： MOSS ROBERT H ,  SWINEHART CARL F ,  SPICUZZA WILLIAM F

IPC: C01F5/28 ,  G02B1/00

CPC classification number: G02B1/00 ,  C01F5/28 ,  C01P2002/01 ,  C01P2002/82 ,  C01P2004/51 ,  C01P2004/61

Abstract: A process is disclosed for converting basic magnesium carbonate into pure hot-pressable magnesium fluoride such as is used for the hot-pressing of infra-red radiation transmitting optical bodies. The process includes contacting a slurry of basic magnesium carbonate with carbon dioxide to form enough magnesium bicarbonate or hydrates of magnesium carbonate, in situ, to alter the particles in the slurry. Carbonation of the slurry increases solubility of the solids by establishing an equilibrium relationship in solution between the unstable magnesium bicarbonate and hydrates of magnesium carbonate particles. When the carbonated slurry is contacted with a slight excess of hydrofluoric acid it precipitates solid particles of fine hydrous magnesium fluoride. Neutralization of excess hydrofluoric acid is effected with ammonium hydroxide. The solid particulate precipitate is dried and calcined to yield hot-pressable magnesium fluoride powder of exceptional purity and consistent quality. A hot-pressable magnesium fluoride powder has been prepared which has a specific and uniform refractive index, nD 1.3850 at 20* C; the powder is made up of primary particles the majority of which have an average particle diameter of greater than 5 Mu (microns), permitting the hot-pressing of the powder without grinding it.