Magnetofluids and Their Manufacture.
U S Pat 3 764 540 1973 Oct; :
Magnetofluids from nonmagnetic precursor compounds are produced which require reduced grinding time in the manufacturing process. A 200-g sample of fe2o3 powder was reduced to fe0.91O weighing approximately 184 g. It was removed from the furnace crucible and quenched to room temperature. 100 Ml of oleic acid then was added, and the slurry was ball milled. A true colloidal suspension fluid resulted with a specific gravity of 0.806 and a viscosity of 2.87 Cp. The fluid exhibited a negative magnetic response; it was converted by refluxing at 250 deg. C into a suspension of magnetite and fe which exhibited a strong magnetic response and a decreased viscosity (0.806 Ml). (Ed.: Evidently should be cp; numbers also may be wrong, as they duplicate sp.Gr. Quoted above)
U.S. Pat. 3,764,540; Oct. 9, 1973; Chem Abstr. 79:141,010W