a depolymerized - carboxyalkyl polysaccharide formed by de polymerizing a polysaccharide having from 0 . 5 to 3 . 0 degrees of substitution and reducing the molecular weight of said polysaccharide before or after said depolymerizing provides a biodegradable scale inhibitor useful to prevent deposition of scale comprising , for example , calcium , barium , sulfate and salts thereof . the depolymerized carboxyalkyl polysaccharide is particularly useful in off shore oil production squeeze treatments and in the treatment of scale formed in industrial water treatment .