Abstract: Provided herein is a device useful for measuring the fineness of a dispersion of particles in a liquid vehicle. A device according to the invention includes a light source, a means for mounting a film of said vehicle of increasing thickness, and a means for producing an electronic image of said film, in which these elements are positioned relative to one another so that the light the imaging means receives is predominantly light reflected from regions of the surface of said film which are disrupted by protruding particles. This is achieved by configuring the device so that the image producing means is aimed into the dark field below the light source, with the image producing means being directed generally at an angle below the angle of reflection of any light reflected from undisrupted regions of the surface of the film.

Abstract: Provided herein is a device useful for measuring the fineness of a dispersion of particles in a liquid vehicle. A device according to the invention includes a light source, a means for mounting a film of said vehicle of increasing thickness, and a means for producing an electronic image of said film, in which these elements are positioned relative to one another so that the light the imaging means receives is predominantly light reflected from regions of the surface of said film which are disrupted by protruding particles. This is achieved by configuring the device so that the image producing means is aimed into the dark field below the light source, with the image producing means being directed generally at an angle below the angle of reflection of any light reflected from undisrupted regions of the surface of the film.

Abstract: A process for the treatment of titanium dioxide pigment in which there is added to a slurry of the pigment a compound of silicon, of aluminium, of zirconium and of titanium, changing the pH of the slurry to 7.5 to 8.5 prior to adding a compound of silicon, an acidic compound of aluminium and an alkaline compound of aluminium, thereby producing a coated pigment.

Abstract: A process for the production of the highly durable titanium dioxide pigment in which the pigment is coated with a phosphate, a silicate and a hydrous oxide of zirconium and aluminium in specified carefully controlled amounts and order of deposition.

Abstract: A process for the treatment of titanium dioxide pigment which involves adding to a pigment slurry a compound of phosphorus, of aluminium, of zirconium, of titanium and of silicon, adjusting the pH of the slurry to a value of from 3.5 to 4.5, followed by adding to the slurry a compound of phosphorus of an alkaline reacting compound of aluminium prior to the addition of mineral acid to adjust the pH of the slurry to a value of 6.5 to 8.