Abstract: A precipitated calcite of substantially spherical morphology having an average spherical diameter of from 2 to 10 microns and a specific surface area of from 1 to 15 square meters per gram is prepared by introducing carbon dioxide gas into an aqueous slurry of calcium hydroxide containing dissolved polyphosphate in the amount of from 0.1 to 1.0 percent, calculated as grams of phosphorus per 100 grams of the calcite equivalent of the calcium hydroxide, the starting temperature of the carbonation being 15.degree. to 50.degree. C. The spherical calcite is particularly suitable for use in dull finish coated paper.

Abstract: A process for the preparation of finely divided precipitated calcite in which carbon dioxide is introduced into an aqueous calcium hydroxide slurry containing anionic organopolyphosphonate polyelectrolyte with the carbonation started at a temperature above about 7.degree. and below about 18.degree. C.

Abstract: A thermally stable oxide product comprising particulate iron oxide coated with an insoluble metal metaphosphate in the amount of at least 1 percent by weight based on the weight of said product, wherein said iron oxide is hydrated ferric oxide or ferroso-ferric oxide, and wherein said metal is aluminum, barium, calcium, magnesium, iron or zinc, and said product is characterized by a procedural decomposition temperature of at least about 230.degree. C. for the hydrated ferric oxide and about 180.degree. C. for the ferroso-ferric oxide and a heat soak .DELTA.E of at most about 4.0 for the hydrated ferric oxide and about 5.0 for the ferroso-ferric oxide. A process claim is also asserted.