Orthorhombic lead chromate pigments of greenish hue
AssigneeCiba-Geigy Corporation
InventorsLeonardus J. H. Erkens, Gerben P. Algra, Jacobus M. H. Snijders, Herman J. J. M. Geurts, Andre Pugin
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Abstract
The invention relates to orthorhombic lead chromate pigments of greenish hue, which contain lead chromate and lead sulfate in the weight ratio of 60:40 to 100:0, and which are characterized by a tinctorial strength of 0.067 to 0.103 at a standard depth of shade of 1/25 in accordance with DIN 53 235 and by an opacity factor Y.sub.black /Y.sub.white of 0.78 to 0.87. These pigments are obtainable by mixing an aqueous solution of a chromate and, if necessary, of a sulfate, under high turbulence.
Claims14
An orthorhombic lead chromate pigment of greenish hue, which contain lead chromate and lead sulfate in the weight ratio of 60:40 to 100:0, and which is characterised by a tinctorial strength of 0.067 to 0.103 at a standard depth of shade of 1/25 in accordance with DIN 53 235 and by an opacity factor Y.sub.black /Y.sub.white of 0.78 to 0.87, which pigment is obtainable by mixing an aqueous solution of a lead salt with an aqueous solution of a chromate and, when the pigment contains lead sulfate, of a sulfate, under high turbulence.
A process for the preparation of an orthorhomic pigment which contains lead sulfate in the weight ratio of 91:9 to 100:0, which process comprises mixing an aqueous solution of a lead salt with an aqueous solution of a chromate and, when the pigment contains lead sulfate, of a sulfate, in a high-performance stirring apparatus.
Dependencies are inferred from the claim text.