Patent ID: 8779119

Claim:
A metal salt of a crosslinked cellulose represented by the following formula (I), wherein the degree of substitution of the hydroxyl group of glucose unit of the crosslinked cellulose by a functional group “A” is 1 or more: R—O—A (I) wherein R represents a crosslinked cellulose residue and A represents —SO 3 H, wherein the degree of crosslinking is 0.174-0.3, both inclusive, and the degree of substitution n is calculated by the following equation: n =(the molecular weight of one unit of crosslinked cellulose)* Y÷[y/m −((molecular weight of SO 3 H)−(atomic weight of one hydrogen))* Y] Y: the elemental analysis value of sulfur, y: the atomic weight of sulfur, m: the atomic valence of sulfur.