Abstract: A process for the preparation of dyes which contain sulfonic acid groups and have a low electrolyte content, wherein an aqueous solution or suspension, which may or may not contain inorganic salts, of the dye containing sulfonic acid groups is(a) mixed with an amount, equivalent to the said dye, of a non-emulsifying, water-insoluble amine of a total of 12 to 40 carbon atoms, which forms, with the said dye, a salt which is sufficiently lipophilic for it to separate spontaneously from the aqueous phase,(b) the pH is brought to <5 with an acid and the batch is mixed thoroughly,(c) the two resulting phases of different density are separated, and(d) the phase which consists of the lipophilic ammonium salt of the dye is mixed, with or without prior washing with water, with a water-soluble base whose sulfonate salt is to be prepared, and with water, the resulting phases are separated, and the salt is left in the aqueous solution or is isolated therefrom.

Abstract: 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.

Abstract: Sludges are flocculated by the addition of a polymer which is prepared by the homopolymerization of N-vinylformamide in the presence of a free-radical polymerization initiator to give a poly-N-vinylformamide, followed by hydrolysis of from 10 to 90% of the formyl groups in the poly-N-vinylformamide.

Abstract: Production of formaldehyde by oxidizing dehydrogenation of methanol in the presence of a silver catalyst and a tertiary or secondary amine. The formaldehyde which can be prepared by the invention is a disinfectant, tanning agent, reducing agent and valuable starting material for the production of synthetic resins, adhesives and plastics.