Rhone-Poulenc Industries

Rhone-Poulenc Specialites Chimiques

Marcel Peltier

Jean Khaladji

Francis Tastu

Pierre Melard

Rare earth glass-polishing compositions of improved homogeneity and reproducibility are prepared by (a) simultaneously continuously admixing a cerium salt solution, a basic solution and a solution of at least one acid and/or one salt, the anion or anions of which being adopted to form insoluble rare earth compounds, the number of equivalents of base being equal to or greater than the number of equivalents of cerium, and the pH of the reaction medium being greater than about 6; (b) filtering the precipitate which results from the reaction medium; (c) drying said recovered precipitate; and (d) calcining said dried precipitate.

Rare earth polishing compositions

Cerium based glass polishing compositions, well adapted for the polishing, e.g., of optical glass, are comprised of (i) at least one crystalline phase of CeO.sub.2 type, and (ii) a crystalline phase which comprises a rare earth pyrosilicate having the formula Ln.sub.2-x Ce.sub.x Si.sub.2 O.sub.7, wherein Ln is at least one lanthanide or yttrium and x is a number ranging from zero to less than 2.

Cerium based glass polishing compositions

Rare earth glass-polishing compositions of improved homogeneity and reproducibility are prepared by (a) simultaneously continuously admixing a cerium salt solution, a basic solution and a solution of at least one acid and/or one salt, the anion or anions of which being adopted to form insoluble rare earth compounds, the number of equivalents of base being equal to or greater than the number of equivalents of cerium, and the pH of the reaction medium being greater than about 6; (b) filtering the precipitate which reuslts from the reaction medium; (c) drying said recovered precipitate; and (d) calcining said dried precipitate.

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La Rochelle, France

Marcel Peltier