| 摘要 |
PROBLEM TO BE SOLVED: To obtain a hydrate iron oxide having narrow particle size distribution and heightened in aspect ratio by adding sulfurous acid (sulfite) into a suspension containing ferrous hydroxide, which is obtained by adding an alkali aq. solution into a ferrous salt aq. solution, to oxidize, supplying an alkali and oxidizing to grow hydrate iron oxide. SOLUTION: The suspension containing ferrous hydroxide is obtained by adding the alkali aq. solution in a quantity equal to or below the neutralization equivalent weight to the ferrous salt into the ferrous salt aq. solution having 10-100g/l Fe concentration. A suspension containing the hydrate iron oxide of a seed crystal is obtained by adding 0.1-1.0mol% sulfurous acid (sulfite) to the ferrous salt neutralized and precipitated by the seed crystal reaction into the suspension and allowing to react in the presence of an oxygen- containing gas at 20-60 deg.C for 60-600min. The hydrate iron oxide is obtained by, if necessary, adding the ferrous salt aq. solution and oxidizing while supplying the alkali to keep to pH2-6. |
