Abstract: The subject invention relates to the use of certain iron oxide spinels to color plastics. The iron oxide spinels are acicular particles having an average length of less than 0.1 micron and are represented by the formulae XFe.sub.2 O.sub.4 or YFe.sub.5 O.sub.8 in which X is a metal selected from the group consisting of Zn, Sn, Cu, Ca, Cd, Co, Ba, Sr, Mg, Al, and Mn, and Y is Li. The spinels are incorporated into plastics by methods which are known to those of ordinary skill in the art. The resulting plastics can be made with a wide variety of colors and can be used to coat surfaces without hiding the underlying surface.

Abstract: A yellow pigment capable of withstanding elevated temperatures such as 200.degree. C. is provided by the formation of a spinel of iron and other metal, such as Mg, Zn, and Sn. The pigment is made by a method which does not involve a step of calcining at high temperature, such as 600.degree. to 1100.degree. C., but rather involves precipitation from aqueous solution and subsequent exposure to elemental oxygen, as by aeration, to form submicron-sized particles of desired spinel.

Abstract: Improved transparent iron oxide pigments having increased color strength are achieved through the incorporation of fluoride with the crystals or particles of the iron oxide. These pigments may be prepared by the process which comprises reacting an aqueous solution of a water-soluble iron salt with an alkaline precipitating agent wherein a fluoride salt is added to the solution or to the reaction product.

Abstract: A monomeric reactant is adsorbed on the surface of a pigment prior to its agglomeration. The subsequent addition of a polymerization initiator or second reactant produces a coated pigment of improved dispersibility, especially in chemically related polymer binder systems.