PURPOSE: To obtain inorganic powder having extremely suppressed activity, by adsorbing a salt of a polyamino acid on the powder to control the surface activity of the powder, followed by treating the powder with an acidic substance.
CONSTITUTION: When a perfume or drug coexists with inorganic powder such as kaolin, talc, etc., an acidic or basic points of the powder exhibit acidity or basicity, to produce an offensive odor or decomposition. To prevent this, the powder is dispersed into an aqueous solution of a salt of a polyamino acid, so that the salt of polyamino acid is adsorbed on the powder. An acidic substance such as citric acid, etc. in the form of a solution or the substance itself is added to the aqueous solution, the same operations are repeated, and the powder is dehydrated and dried.