Deutsche Gold- Und Silber-scheideanstalt Vormals Roessler

Karl Trebinger

Helmut Reinhardt

Gottfried Kallrath

Finely divided hydrophobic silica and silicates are prepared by precipitating of alkali silicate solutions with mineral acids or metal salt solutions and treated with organohalosilanes. To the acid precipitation suspension recovered in known manner there is added as a hydrophobizing agent an organohalosilane, preferably at about 50.degree. to 90.degree. C., the precipitated product filtered, washed and dried and there subjected to a temperature of 300.degree. to 400.degree. C. There is used as the organohalosilane a prepolycondensed organohalosilane or a mixture of prepolycondensed organohalosilanes.

Process for hydrophobization of finely divided silica and silicates

Finely divided hydrophobic silica or silicate is produced by treating the dry, moving particles with an organic silane at elevated temperature. The silica or silicate which had been prepared by wet precipitation or pyrogenically and which is in powdered form is heated to a temperature of about 200.degree. to 300.degree. C. with agitation and is brought to a fluidized condition and then is treated dropwise with an organosilane which is stable and boils below 300.degree. C.

Process for hydrophobizing silicas and silicates with organosilanes

Berlin blue is produced by converting (a) calcium ferrocyanide, sodium ferrocyanide or magnesium ferrocyanide with (b) an iron II salt at a pH below 7 to an acidic iron II salt of ferrocyanic acid FeH.sub.2 [Fe(CN).sub.6 ]. The calcium or sodium ions can be washed out of the precipitate of the ferrocyanic salt. The precipitate is treated with (c) an inorganic or organic potassium salt to form Berlin white and then oxidized to Berlin blue. Alternatively, (a), (b) and (c) can be reacted together at a temperature of 20.degree. to 60.degree.C. to form Berlin white directly.

Process for the production of Berlin blue

Voluminous precipitates or suspensions are contacted countercurrently with liquid purification or extraction agents that hold the continuously supplied precipitate or suspension in the upwardly flowing liquid in a kind of fluidized bed. A suitable apparatus is also described.

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Wesseling, Germany

Karl Trebinger