Abstract: The present invention provides an improved process for coating titanium dioxide with precipitated alumina (aluminum oxide) for use as a pigment in plastics wherein a first coating of amorphous alumina is precipitated onto the titanium dioxide and then a second coating of crystalline alumina is precipitated over the first coating. In operation, the pH of an aqueous slurry of titanium dioxide pigment is adjusted to be within a first pH range as the first alumina coating is effected by adding an amount of sodium aluminate to the aqueous slurry and then the pH of the slurry is adjusted to be within a second pH range while a second amount of sodium aluminate is added to form the second coating over the first coating. The present invention also contemplates an improved titanium dioxide pigment having a first coating of amorphous alumina and a second coating of boehmite alumina.

Abstract: The present invention relates to a method for producing an alkali metal pyrophosphate useful, for example, as a plant food. Broadly, the method comprises reacting an alkali metal nitrate and aqueous phosphoric acid in the presence of catalytic amount of a metal oxide at a temperature of at least about 700.degree.C to produce a substantially pure alkali metal pyrophosphate and gaseous reaction products.