Abstract: Method for imparting superior viscosity to an aqueous polysaccharide solution comprises prehydrating polysaccharide in fresh and deionized water. The viscosity imparted to the final aqueous solution by this method is greater than the viscosity of an aqueous polysaccharide solution initially hydrated in hard water. Alternatively, the polysaccharide solution in fresh water may be used alone or diluted with water containing inorganic ions.

Abstract: The specification discloses a process for recovering oil from a subterranean reservoir which process utilizes a thickened flooding liquid containing polysaccharide B-1459. In the process the polysaccharide B-1459 is imparted with superior viscosity by first prehydrating it with fresh or deionized water before mixing with another aqueous component, for example brine water containing large amounts or inorganic ions, that is, hard water. The invention comprises the polysaccharide B-1459 which has been prehydrated in the fresh or deionized aqueous medium and then mixed with hard water. The process for imparting viscosity to polysaccharide B-1459 is an improvement over the prior art in that a higher viscosity is obtained while using the same amount of polysaccharide that has been obtained by hydrating the polysaccharide in hard or brine water initially.