METHOD OF PRODUCING MAGNESIA ADDITIVE Russian patent published in 2015 - IPC C01F5/38 C01F5/00 

FIELD: chemistry.

SUBSTANCE: when decomposing caustic magnesite with nitric acid, taken in stoichiometric excess, followed by separation of the non-decomposed residue from magnesium nitrate solution by filtering, decomposition is carried out in two steps. At the first step, caustic magnesite, in the presence of fluoride or silicofluoride ions, is decomposed with 42-47% nitric acid for 4-6 hours at temperature not higher than 90°C, and at the second step the obtained suspension, before separating the non-decomposed residue, is diluted with water to magnesium nitrate content of 30-40 wt % and held at 70-90°C for not less than 30 min. Content of fluoride or silicofluoride ions is not less than 0.1 wt % in terms of fluorine with respect to the caustic magnesite.

EFFECT: high efficiency of filtering magnesium nitrate suspensions.

5 cl, 3 tbl, 33 ex