Alkali metal zinc monoalkylphosphate, particles thereof, process for preparing the same, and cosmetic containing the same

A process for preparing particles of an alkali metal zinc monoalkylphosphate represented by formula (I):

• ##STR3## wherein R represents a saturated or unsaturated straight-chain or branched hydrocarbon group having from 8 to 32 carbon atoms, and A represents an alkali metal, which process comprises reacting an alkali metal salt of a monoalkylphosphoric acid (II) represented by formula (II):
• ##STR4## wherein R represents a saturated or unsaturated straight-chain or branched hydrocarbon group having from 8 to 32 carbon atoms, said alkali metal salt having a degree of neutralization of from 0.8 to 1.2, with a zinc salt represented by the following formula (III):
• X.sub.m Y.sub.n (III)
• wherein X represents zinc, Y represents zinc, Y represents an inorganic anion or an organic acid anion, and m and n each represent an integer determined by the valence requirements of Y and X, respectively, by salt exchange, and then adjusting the pH of the reaction system to the range of from 2 to 6.