Hoechst Aktiengesellschaft

Gerhard Nolte

Eberhard Preisler

Franz-Josef Dany

Gerhard Kalteyer

Hedwig Prell

Hans-Werner Stephan

Gerhard Mietens

Gunter Reichert

Johannes Holzem

Herbert Panter

Hermann Schrodter

Bernhard Hofmann

Hermann Klein

In the process for the preparation of dicalcium phosphate dihydrate, which has a good compatibility with fluorine and stability to hydrolysis and causes the minimum possible after-thickening when used in tooth-pastes, by reaction of calcium carbonate suspended in water with an aqueous solution of orthophosphoric acid, precipitation of dimagnesium phosphate trihydrate, as a stabilizer, by reaction of aqueous solutions of a magnesium salt and of orthophosphoric acid in the presence of a basic compound and final filtration, drying and grinding of the precipitate, 0.2 to 0.8% by weight of polyphosphoric acid, calculated with respect to the dicalcium phosphate dihydrate precipitated in the reaction mixture, is added to the reaction mixture as a further stabilizer.

Process for the preparation of a dicalcium phosphate dihydrate suitable

In the process for the preparation of dicalcium phosphate dihydrate, which has a good compatibility with fluorine and stability to hydrolysis and causes the minimum possible after-thickening when used in toothpastes, by reaction of calcium carbonate suspended in water with an aqueous solution of orthophosphoric acid, precipitation of dimagnesium phosphate trihydrate, as a stabilizer, by reaction of aqueous solutions of a magnesium salt and of orthophosphoric acid in the presence of a basic compound and subsequent addition of tetrasodium pyrophosphate to the reaction mixture as a further stabilizer and final filtration, drying and grinding of the precipitate, 0.2 to 0.6% by weight of tetrasodium pyrophosphate, calculated with respect to the dicalcium phosphate dihydrate precipitated in the reaction mixture, is added to the aqueous reaction mixture.

The present invention relates to a method for the preparation of electrolytic manganese dioxide in which flocculent nuclei of a manganese oxide hydrate is dispersed in the electrolyte.

Process for the preparation electrolytic manganese dioxide

The disclosure relates to a process for removing molybdenum from aqueous manganese(II)salt solutions by adsorbing the molybdenum on manganese dioxide and separating adsorbend and adsorbate from the purified manganese(II)salt solution. To this end, the disclosure provides for a pH value lower than 5 to be established in the manganese salt solution; for an oxidant capable of oxidizing manganese(II)compounds to manganese(IV)compounds to be added at temperatures between 50.degree. and 80.degree. C., so as to effect oxidation of a small proportion of dissolved manganese(II)salt to manganese dioxide; for resulting precipitate to be allowed to remain in contact over a period of at least 15 minutes with the manganese(II)salt solution, and for the precipitate to be separated from said solution at said temperatures.

Process for removing molybdenum from aqueous manganese salt solutions

The disclosure provides an electrolytic cell sealed in gas-tight and liquid-tight fashion. The cell is comprised of a box-shaped cell tank open at its top and provided with at least one intake duct, at least one overflow duct and at least one discharge duct. A cover is placed on the cell tank and two opposed flanges receiving electrode supporting frames are secured to the inside of the cell tank near the upper end thereof. A chemically resistant and electrically insulating coating is applied to the inside of the cover and cell tank and a plurality of semi-circular recessed grooves spaced apart from each other are formed in the upper rim portion of at least one of the side walls of the cell tank, the recessed grooves receiving semi-circular current beams projecting outwardly. A first elastic packing structurally conformed to the upper rim portion of the cell tank including the recessed grooves is placed thereon and a second elastic packing arranged at the underside of the cover co-operates with the upper side of the current beam and the first elastic packing whereby the electrolytic cell becomes gas tightly sealed. A main current rail is arranged to run outside the cell tank laterally with respect thereto and so as to be spaced therefrom, the rail providing large contact areas supporting the projecting end of the current beams. The electrode supporting frames and the current beams are electrically conducting inside the electrolytic ce

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Erftstadt, Germany

Gerhard Nolte