Phosphoric Acid → Magnesium Phosphate

A solution obtained by diluting 2.7 kg of a 85% by weight solution of phosphoric acid with ion-exchanged water to a total quantity of 100 kg was gradually added with stirring to a solution obtained by adding 2 kg of magnesium hydroxide to 300 kg of ion-exchanged water, and then further adding and dissolving therein 2 kg of diglycerol monocaprate (trade name: “SUNSOFT Q-10 D”; HLB=9.5; monoester content: 85% by weight; specific gravity: 0.9; manufactured by Taiyo Kagaku Co., Ltd.). The pH of the resulting mixture was adjusted to 8 using a handy pH meter manufactured by HORIBA, Ltd. After forming of the salt of magnesium phosphate by neutralization reaction was terminated, the resulting reaction mixture was subjected to solid-liquid separation by centrifugation (3000×g, for 10 minutes), and 4 kg (dry weight basis) of magnesium phosphate of the solid phase portion was collected (average particle size of fine metal particles: about 0.31 μm). The magnesium phosphate was resuspended in ion-exchanged water, to give a magnesium phosphate dispersion composition having a solid content of 10% by weight (20 parts by weight of an emulsifier were contained based on 100 parts by weight of the metal salt). The resulting composition was filled in a clear container, and stored with leaving it at rest for 1 month at normal temperatures. As a result, the composition was excellent in dispersion stability, with no occurrence of separation and precipitation of the constituents.