| 摘要 |
Hydrargillite crystals which are crystallographically pure, regular and have an active area of up to 100 sq. m. per gram are prepared by aging a gel of amorphous alumina protected from drying and containing at least 0.1 gram ions of monovalent anions per gram molecule of Al2O3 in the gel, at a temperature between ambient and 60 DEG C. for at least 2 days, adding the gel thus obtained, which is in the form of hydrargillite crystals, to a solution of sodium aluminate and leaving the hydrargillite crystals to increase in size. Monovalent anions exemplified are NO3- and Cl-. Preferably the ratio of the alumina in the aged gel to the total alumina in the mixture containing the sodium aluminate is up to 20%. The hydrargillite crystals may be allowed to increase in size for a period of from half an hour to 3 days at a temperature between ambient and 70 DEG C., and then may be drained and washed. |
