GB693108A - Process for the production of easily filterable magnesia and ammonium-magnesium-double salt - Google Patents

Abstract

Magnesia is prepared from a solution containing a magnesium and ammonium salt, e.g. the sulphates, representing a mother lye recycling from the process, by simultaneously introducing the solution and gaseous ammonia, the latter in twice the theoretical amount, with continual stirring, into another part of the lye, whereby precipitation of magnesium hydroxide occurs above 50 DEG C, e.g. 60-80 DEG C, up to a concentration of over 15 per cent ammonium salt, filtering off the magnesium hydroxide, expelling excess ammonia by heat or vacuum, adding to the solution solid magnesium salt the same as that present therein to form an ammonium magnesium double salt, filtering and recycling the mother lye. In a modification, instead of adding solid magnesium salt, the ammonium magnesium double salt is recovered by evaporation, and the liquor is then enriched with magnesium salt.