Abstract: A method is provided for forming a film having excellent anticorrosion properties on a metal surface without producing sludge, and without using phosphorus or chromium. In this method, the following steps (a)-(c) are performed on a metal material: (a) degreasing, (b-1) pretreatment if necessary, and (c) which comprises the following steps (c-1) or (c-2). The film-forming step (c-1) is a step for forming a film by bringing the metal material in contact with an aqueous solution comprising at least one of the following compositions (A), (B), (C) or (D): (A) is a monomer comprising a sulfonium group at one end of the molecule. (B) is a water-soluble polymer obtained by homopolymerization or copolymerization of the monomer (A). (C) is an emulsion or water-soluble polymer comprising a sulfonium group obtained by copolymerization of the monomer (A) and a radical-polymerizable unsaturated monomer excluding the monomer (A).

Abstract: A water-dispersible organic clay complex in which a quaternary ammonium ion having both an oxypropylene unit and an oxyethylene unit is present in interlamellar space of an expansible phyllosilicate. This complex is excellent in dispersibility in an aqueous medium and generates excellent water resistance of the resulting coated film when used as a rheology control agent for an aqueous coating composition.

Abstract: There are disclosed a magnetic particle for an immunoassay method, which comprises a core and a coating layer formed on the surface of the core wherein said core comprises an organic polymer matrix and said coating layer comprises a mixed crystal ferrite represented by the formula:M.sub.x Fe.sub.(3-x) O.sub.4wherein M represents at least one metal selected from the group consisting of Mn, Ni, Zn, Co, Cu, Mg, Sn, Ca and Cd, and x is a number satisfying the relation: 0<x<3,and an antigen or an antibody is bound onto the surface of the coating layer and wherein said particle has a particle size of 0.03 to 10 .mu.m, and an immunoassay method using the same.

Abstract: An immunoassay method using magnetic particles comprising a core and a coating layer on the surface thereof, The core comprises an organic polymer and the coating layer comprises an iron oxide type ferrite coating layer. An antigen or an antibody is bound onto the surface of the coating layer and the particle has a particle size of 0.2 to 3 .mu.m.

Abstract: There is disclosed a method for forming a ferrite coatings on a substrate, which comprises:(a) bringing a substrate into contact with water or an aqueous solution, and(b) adding a ferrous ion solution, an oxidizer solution and a pH controller so that pH and an oxidation-reduction potential may be included within the range specified by A (6, -440 mV), B (6, -130 mV), C (11, -430 mV) and D (11, -740 mV) in a pH - oxidation-reduction potential graph.