Benckiser-knapsack Gmbh

Bk Ladenburg Gmbh

Bk Ladenburg Gmbh Gesellschaft Fuer Chemische Erzeugnisse

Bk Giulini Chinie Gmbh & Co., Ohg

Bk Ladenburg Gmbh Gesellschaft Fur Chemische Erzeugnisses

Alexander Maurer

Richard Taenzler

Guenter Raab

Hans-Georg Steinert

Gudrun Raab

Istvan Potencsik

Wilhelm Spatz

Stephan G Kleemann

Detlev Schober

Gerhard Schoenmann

Reinhold Schmitt

Albert Erasmus

Armin Etzel

A process for purification by multistage countercurrent extraction of wet-process phosphoric acid includes the steps of (a) preparing an aqueous phosphoric acid by decomposition of crude phosphates with sulfuric acid and prepurification thereof; (b) providing an organic solvent mixture consisting of one of (A) a water immiscible solvent and a fully water-miscible solvent or (B) a partially water-miscible solvent and a fully water-miscible solvent; (c) extracting water from the acid by contacting with the solvent mixture in a volumetric ratio of acid to solvent mixture of 1:1 to 1:10 at a temperature of 5 to 90&deg; C.; (d) recovering the fully water-miscible solvent by distillation and washing; (e) recycling the fully water-miscible solvent to step (b) to provide a recycled solvent mixture; and (f) repeating steps (c), (d) and (e) with the recycled solvent mixture to provide a phosphoric acid having a preselected degree of purity.

Wet-process technique for refining phosphoric acid

A process for the preparation of a hydroxyapatite, which is suitable as a tooth-cleaning substance, by precipitation from aqueous phosphoric acid and calcium hydroxide solution, in which a calcium-doped phosphoric acid solution is fed to an intensive mixer with a suspension of calcium hydroxide/oxide in a molar ratio of Ca:P=1.667 corresponding to the hydroxyapatite of and reacted there at precipitation temperatures of 60.degree.-100.degree. C., preferably 80.degree.-90.degree. C. and a pH of 4-8, preferably of 6.5-7.5. Also disclosed in a tooth-cleaning substance containing the hydroxyapatite.

Process for the preparation of hydroxyapatite

The present invention provides a process and apparatus for the production of coarse-grained dicalcium phosphate anhydride, at least 95% of which consists of particles with a grain diameter of &gt;45 .mu.m, wherein, at a temperature of 60.degree. to 100.degree. C., a highly reactive calcium component, for example freshly slaked milk of lime or an aqueous slurry or suspension of calcium hydroxide and/or calcium carbonate, is introduced directly into the stirrer zones of a vessel containing aqueous phosphoric acid and having one or more turbulent stirrer zones. An equivalent amount of aqueous phosphoric acid is introduced into another zone of the vessel, the speed of introduction being so regulated that a pH value of 3.0 to 4.5 is obtained in the stirrer zone and the whole batch or a continuously or semi-continuously removed part thereof is cooled to 40.degree. to 60.degree. C. The removed part then is mixed with an additional calcium component, for example milk of lime, to obtain a pH value of from 5.5 to 6.8, the mixture further stirred for 10 to 60 minutes and the resultant course-grained dicalcium phosphate anhydride is filtered off and dried.

Process for the production of coarse-grained, anhydrous calcium

An apparatus for the preparation of alkali metal monofluorophosphates is disclosed. The apparatus includes a melting crucible of a platinum/rhodium alloy, devices for feeding the alkali metal fluoride and alkali metal metaphosphate or alkali metal polyphosphate raw materials into the upper part of the crucible, an outflow orifice for molten alkali metal fluorophosphate in the bottom of the crucible, a corresponding discharge orifice in the furnace, and a cooling arrangement, wherein a direct voltage is applied between the cooling arrangement and the melting crucible which is connected as the anode.

Apparatus for the preparation of alkali metal monofluorhosphates

The invention provides a process for the production of Maddrell's salt, wherein solid sodium dihydrogen phosphate and/or disodium dihydrogen pyrophosphate, containing catalytic amounts of an acid or of an acid-generating compound statistically distributed therein, is brought to condensation at an elevated temperature.

Process for the production of Maddrell's salt

Growing community of inventors

Mannheim, Germany

Alexander Maurer