Basf Aktiengesellschaft

Karl-Ludwig Hock

Wolfgang Habermann

Joachim Kranz

Rolf Schneider

Harry Distler

Helmut Knittel

Peter Hammes

Fritz Brunnmueller

Peter Thoma

Friedrich Brunnmueller

Joachim Felger

Aminonitriles are prepared by reacting a nitrogen compound with formaldehyde and hydrogen cyanide in the presence of an additional acid at a pH below 2 and at from 10.degree. to 70.degree. C., the concentration of the hydrogen cyanide during the reaction being not more than 3 per cent by weight, based on the reaction mixture. The aminoacetonitriles obtained by the novel process are valuable starting materials for the preparation of dyes, fungicides, bactericides, textile assistants, rubber additives, and auxiliaries used in water softening, cosmetics, the photographic industry, the paper industry and the electroplating industry.

Preparation of aminoitriles

Blue iron hexacyanoferrate-III pigments are produced by a process wherein complex iron-II hexacyanoferrate-II (Berlin white) is prepared by electrolysis of an aqueous catholyte solution containing (a) an iron-II salt, (b) an alkali metal salt, an ammonium salt or a mixture of these, and (c) hydrogen cyanide, in an electrolysis cell in which the anode chamber and cathode chamber are separated by an ion exchange membrane, using an electrically conductive aqueous liquid in the anode chamber, and the iron-II hexacyanoferrate-II obtained is then converted to the blue pigment. The process gives Berlin white, which is substantially free from salt, in high yield and high purity. Pollution caused by the process is very low, since only a small amount of salt is produced. Compared with the corresponding blue pigments produced by prior art processes, the pigments obtained give purer colorations with better gloss, and are of higher color strength.

Production of blue iron hexacyanoferrate-III pigments

Blue iron hexacyanoferrate-III pigments (I) are prepared by anodic oxidation of metallic iron in hydrogen cyanide, or a reaction medium containing hydrogen cyanide, at pH&lt;7 and at an anode potential of .ltoreq.0.76 V (measured against a standard hydrogen electrode) to complex iron-II hexacyanoferrate-II compounds (II), which are then oxidized to (I) in a conventional manner. The oxidation of (II) is advantageously carried out with air or oxygen at pH 0-4 and at from 70 to 95.degree. C., but can also be carried out at pH&gt;8. The process gives readily dispersible pigments (I) which are of high color strength and give brilliant, glossy colorations.

Preparation of blue iron hexacyanoferrate-III pigments, and the pigments

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Ludwigshafen, Germany

Karl-Ludwig Hock