Abstract: Iron blue characterized by an ammonium content of .+-.5.5 weight %, a potassium content of <0.1 weight %, a sodium content of <0.1 weight %, a color strength in a toluene intaglio printing ink up to 15% greater than the standard Vossen blue 705/80 (calculated in accordance with DIN 53 234) and the color spacings (determined in accordance with DIN 6174 relative to Vossen blue 705/80 as standard) of.DELTA.a*:6.5.+-.0.5.DELTA.b*:1.3.+-.0.3.DELTA.c*:-1.5.+-.0.5It is prepared by placing an aqueous solution of sodium hexacyanoferrate (II) in a reaction vessel at a pH of 7.0 and a concentration of 45.+-.5 g/l, calculated as Fe(CN).sub.6 together with ammonium sulfate having a concentration of 14.+-.1 g/l at a temperature of 22.degree.-23.degree. C., adding an aqueous iron-II sulfate solution at a pH of 2.0, a concentration of 100.+-.10 g/l, and a temperature of 22.degree.-23.degree. C., and precipitating the white dough until an excess of iron up to 1.4-1.

Abstract: Iron blue pigment (DIN 55 906) is produced by white paste precipitation and subsequent oxidation of the white paste. Alakli or alkali metal ions i.e. sodium and potassium ions, cyanide or complex iron cyanide ions and iron ions are used as raw materials. The iron blue pigment according to the invention is characterized by a potassium content of 0.5-4.5% by weight, preferably 0.5-2.0% by weight, a sodium content of 0.2-1.0% by weight, an ammonium content of 2.0-4.5% by weight, preferably 3.0-4.5% by weight, a coloring power in accordance with DIN 53 204 and DIN 53 234 of 5-15% above the Vossen Blue 705 Standard and the following color intervals (determined in accordance with DIN 53 204 and DIN 53 234 in conjunction with DIN 6174, in relation to Vossen Blue 705 as standard):.DELTA.L: -0.7 to -1.5.DELTA.a: -0.5 to 1.5.DELTA.b: -0.6 to -2.3.DELTA.C: +0.5 to 2.

Abstract: Iron blue pigment (DIN 55 906) is produced by white paste precipitation and subsequent oxidation of the white paste. Alkali or alkali metal ions i.e. sodium and potassium ions, cyanide or complex iron cyanide ions and iron ions are used as raw materials. The iron blue pigment according to the invention is characterized by a potassium content of 7.0-9.0% by weight, preferably 7.6-9.0% by weight, a sodium content of 0.5-2.0% by weight, preferably 0.5-1.5% by weight, a coloring power according to DIN 53 204 and DIN 53 234 of 5-15% above the Vossen Blue 705 Standard and the following color intervals (determined in accordance with DIN 53 204 and DIN 53 234 in conjunction with DIN 6174, in relation to Vossen Blue 705 as standard):.DELTA.L: -0.7 to -1.5.DELTA.a: -0.5 to +0.3.DELTA.b: -0.6 to -2.3.DELTA.C: +0.5 to +2.

Abstract: 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.