Highly transparent alumina hydrate particles having a large pore volume, having
a pore diameter which falls in a specified range and, when formed into a high-concentration
dispersion sol, exhibiting a low viscosity are provided. Alumina hydrate particles
having a composition represented by the general formula xM2O.y(NH4)2O.Al2O3.zH2O
(210-4x2510-4, 0.110-4y2010-4,
0.6z2.5, M represents an alkali metal; when the alkali metal is
in the form of M2O, x is the number of moles thereof per mol of Al2O3;
when ammonia is in the form of (NH4)2O, y is the number of
moles thereof per mol of Al2O3; and z is the number of moles
of hydration water (H2O) per mol of Al2O3), the
alumina hydrate particles having an average particle diameter of 0.02 to 0.2 m,
a total pore volume of 0.5 to 1.5 ml/g, and a volume of pores whose diameter is
from 15 to 30 nm ranging from 0.3 to 1.0 ml/g.
