. . . "in which 40%-60%, preferably 50%-55%, of the uronic units are those of iduronic acid, R, R??? e R??? represent hydrogen or a SO3 ??? group, for a sulfation degree of from 2 to 4, q is an integer from 2 to 17, advantageously from 2 to 14, preferably from 2 to 11, presents an unit (a???) as defined above at the reducing end of the majority of its chains and the corresponding cation is a chemically o" .