Basf Aktiengesellschaft

Siegfried Schreiner

Bernd Leutner

Erfried Voelkl

Gerd Wunsch

Volker Kiener

Max Appl

Wilhelm Goesele

Gert Treiber

Werner Ostertag

Hans-Ulrich Schlimper

Jaroslav Melzer

Eckhard Hetzel

Klaus-Dieter Hoppe

Siegmar Lukas

Rudi Waibel

Gerhard D Molin

Gotthard Scizi

Hartwig Koester

Wash solutions containing Fe(II) and Fe(III) chelate complexes and used for removing NO.sub.x from waste gases are regenerated by treatment with sodium tetrahydroborate.

Regeneration of wash solutions containing Fe(II) and Fe(III) chelate

Stabilized water-containing sodium dithionite formulations which have been rendered alkaline have the consistency of a pumpable paste. They additionally contain readily soluble sodium salts and/or potassium salts which are inert to sodium dithionite and whose water-solubility at 20.degree. C. exceeds 500 g/l. These salts are present in the aqueous phase in an amount of not less than 200 g/l. The pastes are useful reducing agents.

Stabilized water-containing sodium dithionite formulations which have

Sodium dithionite formulations containing inert organic liquids have the consistency of a pumpable paste.

Stabilized sodium dithionite formulations containing inert organic

In a process for the manufacture of sodium dithionite by reacting sulfur dioxide with sodium formate and aqueous sodium hydroxide solution in the presence of methanol, an aqueous methanolic solution of sodium formate is first produced by reacting carbon monoxide with sodium hydroxide solution in an aqueous medium, containing from 1 to 50% by weight of methanol, based on the amount of water, at from 80 to 120.degree. C. under a pressure of from 10 to 40 bars. The resulting aqueous methanolic solution can be reacted directly, in the conventional manner, with sulfur dioxide and aqueous sodium hydroxide solution to give sodium dithionite.

Manufacture of aqueous methanolic solution of sodium formate

Concentrated dithionite solutions are produced by cathodic reduction of an aqueous solution, containing sulfite and/or bisulfite, which is circulated by pumping. The cathode and anode chambers are separated from one another by a permselective cation exchanger membrane. The catholyte must be circulated at least 10 times per hour and the selective catholyte volume outside the cell, defined as

Continuous manufacture of sodium dithionite solutions by cathodic

For the preparation of anhydrous sodium dithionite by the reaction of sulfur dioxide with sodium formate and caustic soda in the presence of organic solvents, sulfur dioxide is passed, together with the formate, into a liquid containing all of the caustic soda required for the reaction. This initial liquid may contain, in addition to the caustic soda, a portion of the sulfur dioxide or formate required for the reaction.

Manufacture of sodium dithionite

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Siegfried Schreiner