A slurry containing abrasive grains and a liquid medium, the abrasive grains including first particles and second particles being in contact with the first particles, the first particles containing ceria, the first particles having a negative zeta potential, the second particles containing a hydroxide of a tetravalent metal element, and the second particles having a positive zeta potential.

The present invention is a method of producing silicon compound coated oxide particles in which at least a part of a surface of a metal oxide particle is coated with a silicon compound, wherein wettability and color characteristics are controlled by controlling a ratio of SiOH bonds contained in the silicon compound coated oxide particles. By the present invention, silicon compound coated oxide particles having controlled wettability such as hydrophilicity, water repellency or oil repellency, and controlled color characteristics of either reflectivity, molar absorption coefficient or transmittance can be provided.

A method for the precipitation of rare earth sulphate, the method including subjecting a crude rare earth sulphate solution to precipitation in the presence of a water soluble, volatile, organic compound to produce a rare earth sulphate precipitate and an acidic supernatant. The organic compound is preferably selected from the group consisting of methanol, ethanol, iso-propanol, tert-butanol, acetone or mixtures thereof, and is preferably methanol. Preferably, the organic compound is used in the precipitation at a weight ratio of between 0.25:1 to 1.5:1, and preferably 0.5:to 1.25:1, with the crude sulphate solution.

A method for the precipitation of rare earth sulphate, the method including subjecting a crude rare earth sulphate solution to precipitation in the presence of a water soluble, volatile, organic compound to produce a rare earth sulphate precipitate and an acidic supernatant. The organic compound is preferably selected from the group consisting of methanol, ethanol, iso-propanol, tert-butanol, acetone or mixtures thereof, and is preferably methanol. Preferably, the organic compound is used in the precipitation at a weight ratio of between 0.25:1 to 1.5:1, and preferably 0.5:to 1.25:1, with the crude sulphate solution.

A composition based on cerium and niobium oxide in a proportion of niobium oxide of 2% to 20% is described. This composition can include zirconium oxide, optionally 50% of cerium oxide, 2% to 20% of niobium oxide, and at most 48% of zirconium oxide. Also described, is the use of the composition for treating exhaust gases.

The present invention relates to silicon-compound-coated fine metal particles, with which surfaces of fine metal particles, composed of at least one type of metal element or metalloid element, are at least partially coated with a silicon compound and a ratio of SiOH bonds contained in the silicon-compound-coated fine metal particles is controlled to be 0.1% or more and 70% or less. By the present invention, silicon-compound-coated fine metal particles that are controlled in dispersibility and other properties can be provided by controlling the ratio of SiOH bonds or the ratio of SiOH bonds/SiO bonds contained in the silicon-compound-coated fine metal particles. By controlling the ratio of SiOH bonds or the ratio of SiOH bonds/SiO bonds, a composition that is more appropriate for diversifying applications and targeted properties of silicon-compound-coated fine metal particles than was conventionally possible can be designed easily.

A highly stable gas sensor capable of detecting carbon dioxide is provided. A carbon dioxide gas sensor includes an insulating substrate and a gas sensing layer formed on one major surface of the insulating substrate via electrodes, in which the gas sensing layer comprises one or more rare earth oxides represented by Ln.sub.2O.sub.3, Ln being at least one rare earth metal element selected from Sc, Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Pr, Yb and Lu, and a method for producing the gas sensor are provided.

The present invention concerns a process for the production of metal doped cerium compositions comprising a cerium oxide and a metal oxide by precipitation. The invention also concerns metal doped cerium compositions providing high crystallites size and exhibiting high thermal stabilities, which may be used as a catalytic support or for polishing applications.

These surface-modified metal compound particles have metal compound particles the surfaces of which are modified by: at least one first carboxylic acid selected from the group consisting of a methacrylic acid, an acrylic acid, and a propionic acid; and at least one second carboxylic acid selected from the group consisting of a C6-C16 fatty acid and a C7-C32 monovalent carboxylic acid having at least one benzene ring, wherein at least a portion of the first carboxylic acid is a carboxylic acid type in which a hydrogen atom of the carboxy group is not dissociated as an ion.

Provided is a porous molding which is capable of removing ions in water to be treated, in particular, phosphorus ions at a very high liquid-permeation rate of at least SV 120 hr.sup.1, and which has a large adsorption capacity. The porous molding according to the present invention comprises an organic polymer resin and an inorganic ion adsorbent, and is characterized in that a total volume of pores having a pore diameter of 1-80 nm as measured by a nitrogen adsorption method is 0.05-0.7 cm.sup.3/g per unit mass of the inorganic ion adsorbent.