Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler

Everhard Gratzfeld

Helmut Reinhardt

Eva Clausen

Ferrocyanide blue is produced by reacting an aqueous ferrocyanide solution with an iron II salt and subsequently aging of the precipitate at elevated temperature and optionally at elevated pressure as well as oxidation in acid medium. The improvement comprises simultaneously leading the aqueous solution of ferrocyanide and the ferrous salt solution into a water receiver, whereby optimum mixing occurs during the precipitation and whereupon the precipitate formed, the so-called white stage is aged in known manner directly in the reaction medium in the presence of the salts formed in the reaction at elevated temperature and optionally under pressure and likewise in known manner is converted into Berlin blue by oxidation in acid medium.

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Wesseling, Germany

Everhard Gratzfeld