Abstract: A magnetic toner comprises a binder resin and a magnetic iron oxide. The magnetic iron oxide has a silicon content of 0.1-1.5 wt. % based on the iron contained therein and is in the form fine particles containing the silicon preferentially in the inner part thereof. Because of these features, the magnetic iron oxide particles have a sharp particle size distribution, have uniform surface properties including those under various environmental conditions and freeness from agglomeration, have a good black hue, and are uniformly dispersed in the binder resin to provide a magnetic toner having uniform properties particularly suited for electrophotography.

Abstract: A dry developer for developing electrostatic images comprises (a) toner particles comprising 100 parts by weight of a binder resin and 1-20 parts by weight of polyalkylene having a ratio of weight average molecular weight to number average molecular weight of 2.0-10.0 and Z average molecular weight determined by gel permeation chromatography of 10,000-200,000, and containing 5-60% by weight of a component soluble in n-hexane at boiling point, kinetic friction coefficient of the toner particles being 0.20-0.50, and (b) non-magnetic inorganic fine powders having BET specific surface area according to a nitrogen adsorbing method of 0.5-500 m.sup.2 /g.An image forming method comprises using the dry developer to develop electrostatic latent images on a photosensitive member having a surface hardness of 8 g or more, transferring the developed images to a receiving member, and removing the toner particles remaining on the photosensitive member by a cleaning means accompanying abrasion.

Abstract: A developer for developing electrostatic latent images, comprising toner particles and particles of a fluorine-containing substance as represented by a vinylidene fluoride polymer having a specific randomness in molecular structure or crystalline structure. The randomness of the vinylidene fluoride polymer is defined by the absorption peak ratio in the F.sup.19 nuclear magnetic resonance spectrum in acetone or by the absolute .beta.-crystal content of the vinylidene fluoride polymer. The vinylidene fluoride polymer provides a friction reducing characteristic to the developer while retaining good developing characteristic under various conditions.

Abstract: A process for polymerizing ethylene or copolymerizing ethylene with an .alpha.-olefin in the presence of a catalyst comprising: (A) a solid catalyst ingredient obtained by contacting (1) a solid reaction product prepared by reacting (a) a reaction product of an aluminum trihalide with an organic compound containing an Si--O bond and/or an ether compound and (b) a magnesium alcoholate with (2) a tetravalent titanium compound containing at least one halogen atom or further (3) an electron donor compound, and (B) an organo-aluminum compound.