Hoechst Aktiengesellschaft

Hermann Schrodter

Albert Braun

Gero Heymer

Franz-Josef Dany

Hans-Werner Stephan

Gerhard Nolte

Gerhard Kalteyer

Hedwig Prell

Friedrich-Wilhelm Kampmann

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.

Process for the preparation of a dicalcium phosphate dihydrate suitable

An agent for desulfurizing molten metals, in particular molten iron, comprises a CaC.sub.2 /CaO crystal blend with a maximum of 62% by weight of CaC.sub.2, gas-evolving substances and 0 to 44% by weight of metallic magnesium as the components. For desulfurizing molten metals, in particular molten iron, using this agent, either the mixture comprising both the CaC.sub.2 /CaO crystal blend and gas-evolving substances, and the magnesium, are fluidized separately and the two fluidized products are combined immediately before they enter the melt, or the CaC.sub.2 /CaO crystal blend, gas-evolving substances and magnesium components are fluidized together and the fluidized product is introduced into the melt.

Agent and process for desulfurizing molten metals

Mixture for desulfurizing metal melts based on calcium carbide, calcium oxide, alkaline earth metal carbonates, aluminum oxide, chemically unbonded carbon and alkali metal carbonates, if any. The desulfurizing mixture contains 0.3-4.5 wgt % calcium fluoride as an additional constituent and is produced by grinding the individual constituents jointly in a mill over a period of 3-30 minutes.

Desulfurizing mixture for metal melts, process for making it, and

Production of substantially water-insoluble linear ammonium polyphosphates of the general formula (NH.sub.4 PO.sub.3).sub.n, in which n is a number between 10 and 1000. To this end, substantially equimolecular proportions of ammonium orthophosphate and phosphorus pentoxide are reacted by heating them to temperatures within the range 170.degree. and 350.degree.C in the presence of gaseous ammonia. The reaction is effected while continuously and simultaneously mixing, kneading and comminuting the reaction material in a reactor. The reactor is closed, provided with means for the supply of solid feed material, a gas inlet and a gas outlet, a discharge opening for the removal of final product, and with mixing, kneading and comminuting implements which are rotatably secured to the inside of the reactor.

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Erftstadt, Germany

Hermann Schrodter