Abstract: The pigment comprises a mixture of crystalline phase and an amorphous phase in which the crystalline phase represents from 10 to 70 wt % of the mixture and is constituted by zinc phosphate in the form of substantially spheroidal particles having a maximum size of between 0.5 to 5 microns and the amorphous phase represents from 30 to 90 wt % and comprises ferric phosphate and ferrous phosphate in a mole ratio lying between 1:001 and 1:03.The process comprises a reaction giving ferrous phosphate, partial oxidation thereof and association with zinc phosphate.

Abstract: A pigment composition, particularly adapted for the coloring of plastics materials, consisting of pigments comprising lead chromate, lead sulfochromate, lead molyb-do-sulfochromate, zinc chromate or strontium chromate and being covered by a film formed by an ester of an aromatic or aliphatic tricarboxylic acid and an aliphatic alcohol; the composition is remarkably stable at high temperature and improves the viscosity conditions of the semi-molten mass formed by the composition plus the polymer to be colored.

Abstract: A process for the preparation of lead chromate based pigments comprising the steps of nucleation and growth and wherein:(a) the lead ion is released by means of time and/or temperature conditions allowing the later precipitation of the lead ion absorbed or occluded in the crystal and the rearrangement of said crystal;(b) the lead ion is precipitated by the addition of sodium or potassium salts;(c) the crystal structure is prestabilized by reaction "in situ" of sodium silicate and an ammonium salt;(d) the crystal is hot stabilized by the addition of hydrated oxides of a metal at two valency levels thereof;(e) the crystal stabilization is consolidated by phosphorous salts.