Abstract: Sulfur dioxide is removed from a gas stream by contacting the gas with an aqueous solution containing sulfite anion, magnesium cation, and one or more other cations whose sulfite salts are more soluble than magnesium sulfite. The contacting solution is regenerated with magnesium oxide or hydroxide and then recycled.

Abstract: Peat, lignite, coal, many forms of biomass (land or marine) and solid wastes may have from 1/2 to 30 times as much water associated with the dry solids. Some of this water may be chemically bound or otherwise may be practically inseparable by mechanical means. The solids may be partially oxidized by oxygen or air in the first chemical reactions of a Wet Air Oxidation (WAO) taking place in the presence of the large amount of water at temperatures of 175.degree. C. to 325.degree. C. and pressures of 10 to 100 atmospheres--preferably 240.degree. to 300.degree. C. and 70 to 100 atmospheres. All sulfur in high sulfur coal is oxidized selectively to the sulfate radical; and heat to bring the combustible up to the necessary temperature is supplied by burning part of the combustible itself. The sulfur free coal may be used as conventionally. Residual solids (now 70 to 95% of the original fuel) have a higher heating value on a dry basis, and are mechanically separated from all but 1/2 to 2 pounds of water.

Abstract: A process for reducing the sodium chloride content of crystalline potassium salts without the use of successive recrystallization. The crystalline potassium salts having a sodium chloride content greater than about 0.8 percent by weight are subjected to compacting and crushing to provide a crystalline product having an average particle diameter less than 1.6 millimeters. The crystalline product is leached with a brine at least about 80 percent saturated with said potassium salt and less than 50 percent saturated with sodium chloride to produce a crystalline potassium salt product containing less than about 0.35 percent by weight of sodiumchloride.

Abstract: In the production of iron oxide pigments and substantially iron-free sodium sulphate from iron sulphate by passing an oxygen-containing gas through an alkalized iron sulphate-containing solution at a temperature of about 40.degree. to 100.degree. C.

Abstract: A process for treating a liquid with a gas in a circulatory reactor, in which the gas is introduced by a jet of liquid into a circulating liquid, is entrained downwards in a tube, rises in an annular space surrounding the tube and--if it has not reacted completely--is again entrained downward over the upper edge of the tube. Using the process according to the invention, a very uniform gas distribution and, in the case of heterogeneous reactions, also a very uniform distribution of the suspended catalyst, is achieved over the entire reaction space.

Abstract: Sodium sulfate is purged from a sulfur dioxide removal system involving contact of a sulfur dioxide-containing gas with a solution containing sodium sulfite to absorb sulfur dioxide from the gas. The spent absorbing solution is regenerated by desorbing sulfur dioxide and recycled for further use. To avoid an unduly large build-up of sulfate in the system, at least a portion of the absorbing-desorbing medium, e.g. spent absorbing solution, containing sodium sulfate and a relatively large amount of sodium bisulfite is treated to reduce the amount of water in the medium so that there is precipitated therefrom up to about 10 weight percent undissolved solids containing sodium sulfate in greater concentration than would otherwise be obtained in the absorption-desorption cycle. The insolubles containing sodium sulfate are removed from the liquid, and the liquid can be returned to the sulfur dioxide removal system.

Abstract: Sodium sulfate is purged from a sulfur dioxide removal system involving contact of a sulfur dioxide-containing gas with a solution containing sodium sulfite to absorb sulfur dioxide from the gas. The spent absorbing solution is regenerated by desorbing sulfur dioxide, and recycled for further use. To avoid an unduly large build-up of sulfate in the system, a portion of the absorbing-desorbing medium, e.g., spent absorbing solution, containing sodium sulfate, a relatively large amount of sodium bisulfite, and generally a minor amount of sodium sulfite, is treated to precipitate solids containing sodium sulfate in a concentration which is greater on a dry basis than would otherwise be obtained in the absorption-desorption cycle. The concentration of sodium sulfate in the precipitated solids is increased by providing a portion of the precipitated sodium sulfate-containing solids, e.g. about 25 to 75 weight percent, in solution in the absorbing-desorbing medium treated for sulfate removal.

Abstract: The invention relates to a process for the treatment of an uraniferous ore containing sulfur in the form of sulfates or sulfides with one or more alkaline solutions containing sodium carbonate in the presence of an oxidant, for extracting uranium in the form of soluble uranium salt in said solution.It comprises subjecting the ore, in a first step, to the action of a dilute pre-leach solution of sodium carbonate, whose concentration does not substantially exceed, or by very little, that which is required for the solubilization of the major part of the sulfur initially contained in the ore to convert it to sulfate in the presence of the oxidant and, in a second step, to the action of a leach solution, more concentrated in sodium carbonate, enabling the extraction and solubilization in the medium of the major part of the uranium still contained in the ore, not extracted in the pre-leach medium of the first step.

Abstract: There is disclosed a process for obtaining purer sodium sulfate from a mixture of solids containing sodium sulfate and sodium sulfite. The process involves contacting an aqueous slurry of the sulfate-sulfite mixture with a sulfur dioxide-containing gas under conditions which solubilize a significant amount of the sulfite as sodium bisulfite dissolved in the liquid aqueous phase. The remaining solid phase contains sodium sulfate of greater purity than in the mixture treated with sulfur dioxide. The mixture of sodium sulfate and sodium sulfite which is purified by the process may be obtained advantageously as a purge material from a process for removing sulfur dioxide from a gas stream.

Abstract: Sodium sulfate is purged from a sulfur dioxide removal system involving contact of a sulfur dioxide-containing gas with a solution containing sodium sulfite to absorb sulfur dioxide from the gas. The spent absorbing solution is regenerated by desorbing sulfur dioxide and recycled for further use. To avoid an unduly large build-up of sulfate in the system, at least a portion of the absorbing-desorbing medium containing sodium sulfate and a relatively large amount of sodium bisulfite, e.g. spent absorbing solution, is contacted with a treating gas containing at least a small amount of sulfur dioxide while reducing the amount of water in the medium so that a slurry is obtained having up to about 10, or even up to about 20, weight percent precipitated solids containing sodium sulfate in greater concentration than would otherwise be obtained in the absorption-desorption cycle. Preferably, the sulfur dioxide-containing treating gas is unsaturated with respect to water.

Abstract: Sulfur oxides in the flue gases from a glass furnace are converted to sodium sulfate particles by introducing sodium oxide fume into the hot flue gases immediately downstream of the furnace. The fume is generated by forming a bed of carbonaceous material and sodium carbonate that is caused to react under hot reducing conditions. Sodium gas is thereby produced that burns above the bed to produce sodium oxide fume.

Abstract: In the production of ferric oxide black pigments with the simultaneous recovery of sodium sulphate wherein ferrous sulphate is reacted with an alkaline sodium compound at a pH above about 6 and a temperature above about 50.degree. C., and the pigment formed is separated from the mother liquor containing sodium sulphate, the improvement which comprises conducting the reaction at a sodium sulphate concentration of at least about 20% by weight, after separation of the pigment cooling at least part of the sodium sulphate-containing mother liquor to a temperature of at most about 30.degree. C., thereby to crystallize sodium sulphate decahydrate, and separating the crystals. Air is preferably passed through the reaction solution to oxidize the precipitated pigment and, advantageously, make-up water is added to compensate for water carried off by the air. The end product mother liquor, containing an appreciable amount of sodium sulphate, is employed to dissolve ferrous sulphate for a subsequent cycle.

Abstract: A process for the preparation of a chrome-tanning agent and Glauber's salt from sodium bisulphate contaminated with chromium compounds obtained as by-product from the manufacture of chromic acid from solid sodium dichromate and sulphuric acid, comprising(a) treating an about 20 to 70% aqueous sodium bisulphate solution which contains chromium compounds and is acid with sulphuric acid with sulphur dioxide until all the chromium is present in the form of chromium (III);(b) adding sodium hydroxide to the reduced solution until it has a pH of between about 4 and 5;(c) adding sodium carbonate to the solution to a pH of between approximately 8 and 8.5, thereby precipitating chromium (III) hydroxide;(d) separating off the precipitated chromium (III) hydroxide; and(e) evaporating the filtrate left after removal of the chromium (III) hydroxide to yield solid sodium sulphate.

Abstract: A process for reducing the hydrogen sulfide content of steam, such as steam produced from a subterranean geothermal reservoir, in which the steam is contacted with an aqueous, alkaline solution having a temperature approximating that of the steam to absorb hydrogen sulfide from the steam which is thereafter discharged or utilized in a power generation plant. Hydrogen peroxide is introduced into a cooled portion of the aqueous, alkaline solution to reduce the hydrogen sulfide content thereof and then the aqueous alkaline solution is heated to about the temperature of the steam and recycled into contact with the hydrogen sulfide-containing steam. The temperature of the cooled portion of the aqueous, alkaline solution into which hydrogen peroxide is introduced is such that thermal decomposition of hydrogen peroxide is substantially prevented.

Abstract: A method of carrying out air oxidation comprises substantially continuously feeding liquid and air to an oxidizing tank (A) via a bubble forming device (D) which is fixed at the bottom of the tank, feeding a part of the liquid out of the tank via a lower port to a gas-liquid separating device (B) and then returning the liquid free from gas from the separating device to the oxidizing tank via the bubble forming device. Air separated from the liquid in the separating device is returned to the oxidizing tank and the finished solution is overflowed out from an upper portion of the oxidizing tank. The bubble forming device operates by feeding air into the lower chamber thereof via a nozzle which is aligned with and directed toward an orifice in a partition which divides the bubble forming device into two chambers. The liquid is fed into the lower chamber and the liquid and air are fed as a mixture through the orifice to impinge an upper wall of the upper chamber of the bubble forming device to more fully mix same.

Abstract: In a process for making chlorine electrolytically in which a build-up of nitrogen trichloride occurs in the bottoms of cooling apparatus, a method and apparatus is provided wherein the nitrogen trichloride is dissolved in an organic solvent such as carbon tetrachloride, the chlorine removed, and the solution treated to destroy the otherwise hazardous nitrogen trichloride. The solvent is then separated and recycled to avoid environmentally undesirable waste products.

Abstract: In the process for the production of chlorine and alkali metal hydroxide by electrolysis according to the amalgam process using calcium- and/or sulphate containing crude salt, the calcium and/or sulphate contents introduced into the brine circuit by the crude salt are removed from the brine by precipitation of the double salt Na.sub.2 SO.sub.4 . CaSO.sub.4. Small particles of glauberite may be introduced to the brine to initiate and accellerate precipitation.

Abstract: Isobutylene, hydrogen cyanide and sulfuric acid are reacted to produce tertiary butyl formamide, which is hydrolyzed by sodium hydroxide to produce tertiary butyl amine. The tertiary butyl amine is removed by vaporization and the residue is treated with sulphuric acid and methanol and is distilled to recover formate values as methyl formate or sodium formate. There is additionally recovered crystalline sodium sulfate and a water immiscible yellow organic phase.

Abstract: A method of separating sulfuric acid from spent chlorine dioxide generator liquor. The method comprises simultaneously adding to the spent liquor, a water-soluble organic compound selected from the group consisting of alcohols and ketones, and water. The resulting solid is separated to leave an aqueous solution of sulfuric acid. The method is of particular application in acid and salt cake recovery from the effluent of a chlorine dioxide generator operating at an acid normality of between 6 and 11.

Abstract: A bubble-forming device for gas-liquid contact which can be advantageously used for air oxidation in a liquid phase comprising a housing divided into upper and lower chambers by a partition having an orifice, a liquid inlet in the lower chamber, a gas inlet in the lower chamber having a nozzle directed upward toward the orifice, and having orifices in the side wall of the upper chamber such that gas-liquid mixture will be directed upward through the orifice in the partition toward the ceiling of the upper chamber and directed out the orifices in the side wall. A process for carrying out air oxidation in a liquid phase using said device by creating a large number of fine air bubbles in the liquid.

Abstract: The content of sodium sulfate (and less soluble sulfates) in rock salt (halite) can economically be reduced from levels as high as 5 weight percent to levels as low as about 0.1 weight percent by the process of the invention. The halite is crushed to a certain particle size range and particles less than 0.5 mm in effective diameter are removed while (or after) the crushed material is subjected to attrition washing with a low sulfate, high NaCl brine. The washed, coarse particles are rinsed with a low sulfate brine, drained and dried to an extent appropriate to their contemplated use.

Abstract: A method of obtaining caustic soda and pure sodium chloride from an electrolytic cell liquor containing also sulfate ions including the steps of concentrating the liquor through multiple effect evaporation, cooling the concentrate obtained, separating the sodium chloride and the salt containing sulfate and recovering the caustic soda, whereby during a first stage the liquor is evaporated so as to precipitate only sodium chloride which is removed, in a second stage a solid phase is formed of sodium chloride, sodium sulfate and triple salt of caustic soda, sodium chloride and sodium sulfate, with said solid phase being contacted with a caustic soda solution of less than about 35% by weight concentration, so as to decompose said triple salt, removing the salt containing sulfate, and in a third stage the solution from the second stage is cooled to precipitate said triple salt of caustic soda, sodium chloride and sodium sulfate, which is separated from the caustic soda which does not crystallize and is removed fro

Abstract: Gaseous mixtures containing nitrogen oxides are contacted with an aqueous solution containing sodium sulfite, trisodium imidobissulfate and sodium sulfate while adjusting the pH thereof by sodium hydroxide or sodium carbonate, and sulfur dioxide is contacted therewith simultaneously or thereafter to produce therein disodium imidobissulfate and sodium hydrogensulfate, and then sodium hydroxide is added therein to deposit sodium sulfate 10 hydrate firstly and trisodium imidobissulfate 1 hydrate secondly, and thereafter the mother liquor is recycled as the absorption medium for nitrogen oxides.

Abstract: A process for treating and recovering components from aldol-condensation polyol waste liquor containing sodium formate, water, polyol, and organic by-products comprising A. vacuum crystallizing and removing sodium formate; B. introducing methanol and sulfuric acid; C. distilling to remove and recover methyl formate; D. increasing the pH to about 6.5 to 7.0; E. cooling to precipitate Glauber's salt, polyol and organics; and F. adding water to dissolve and separate the Glauber's salt and recover substantially pure polyol and organics.

Abstract: A cyclic electrolytic process for the manufacture of hydrogen from carbonaceous material such as coal, agricultural wastes and garbage to produce commercial hydrogen. An alakli metal sulfate is reduced to an alkali metal sulfide by reaction of the sulfate and carbonaceous fuel at an elevated temperature. The sulfide and impurities derived from the fuel are digested with an aqueous solution to dissolve the sulfide and separate out the impurities. The solution of the alkali sulfide is added to electrolytic cells in which an electric current is utilized to generate hydrogen at the cathode while oxidizing the sulfide substantially to sulfate at the anode. The cell electrolyte temperature is greater than 150.degree. C and less than 350.degree. C. Under these conditions the polarization problem encountered in hydrogen/oxygen cells is substantially avoided.

Abstract: The efficiency of the Solvay chlorine dioxide producing process is enhanced by the use of a high total acid normality and a single vessel generator-evaporator-crystallizer.

Abstract: Potassium fluoride and silica are reacted with an aqueous solution of hydrofluorosilicic acid. The resulting potassium fluorosilicate is recovered. The potassium fluorosilicate may be further reacted with ammonia in water to form an aqueous mixture of ammonium fluoride and potassium fluoride. The ammonium fluoride is then heated in aqueous solution in the presence of excess potassium fluoride to release ammonia and to form potassium bifluoride. The potassium bifluoride is recovered from solution substantially free from ammonia and heated to release hydrogen fluoride. Alternatively, the recovered potassium bifluoride may be reacted with sodium fluoride to produce sodium bifluoride. The sodium bifluoride is then heated to release hydrogen fluoride.

Abstract: This invention relates to a method for purifying waste air from sulphuric gases, in particular from hydrogen sulphide, carbon disulphide and sulphur dioxide by adsorption and oxidation in a bath containing inorganic oxidizing compounds soluble in water, e.g. hypochlorites of alkali metals, preferably sodium hypochlorite in an amount equivalent to at least 0.1 g, preferably 3-5 g of available chlorine per 1 liter of bath and, if need be additions in the form of chemisorbents such as polyethylene glycol or aliphatic amines in an amount of at least 0.005 g/l of bath, and/or oxidation catalysts such as vanadium and/or palladium salts in an amount of at least 0.01 g/l of bath, and/or organic oxidizing compounds soluble in water such as hydroquinone in an amount of at least 0.1 g/l of bath, with a pH-value of 9-12, in a closed cycle of bath.

Abstract: In the production of anhydrous sodium dithionite by reacting sodium formate, an alkaline sodium compound and sulfurous acid anhydride in hydrous methanol, a process for treating the mother liquor, which comprises adding an alkali to the mother liquor left after the separation of the resulting anhydrous sodium dithionite to adjust its pH to at least 8, separating the solids precipitated, and oxidizing the filtrate with an oxidizing agent.

Abstract: A method of stabilizing aqueous solutions containing alkali metal sulfite or bisulfite and a catalyst therefor by incorporating in said solutions a stabilizing amount of triethylene tetramine. The catalyzed sulfites which are of primary concern in the present instance are those which are used to inhibit or control oxygen corrosion in water treatment, particularly boiler water treatment.

Abstract: Combustion products, especially those from electric power generating installations burning high sulfur fuels are treated to remove solids and then to separate physically sulfur containing constituents, such as SO.sub.2 and/or SO.sub.3 from other gases in the combustion products mixture by means of an ultra high speed gas centrifuge or a gas cyclone. The recovered oxides of sulfur in a heated condition are utilized in any desired chemical reaction. For example, they may be passed over dry NaCl and reacted therewith to yield sodium sulfate and chlorine, both of which can be recovered, and/or they may be passed directly over suitable catalysts in the presence of air to produce a pure grade of sulfur trioxide which can be absorbed in water to manufacture concentrated sulfuric acid.

Abstract: A process for the treatment of aqueous solutions containing cations and anions, including aluminum sulphate and fluoride ions, for the recovery of the fluorine contained in the aqueous solution by means of an ion exchange plant, in which the aqueous solution flows through at least a strong acid cation-exchanger filter step, then a first weak basic anion-exchanger filter step which produces an almost complete separation of the sulphate ions, and after that a second weak basic anion-exchanger filter step which separates out the fluorine ions, and the fluoride is recovered from an eluate obtained during regeneration of the second anion-exchanger filter step.

Abstract: Trialkyl boranes are reacted with compounds containing protons in the presence of catalytic amounts of carboxylic acid derivatives, especially derivatives of t-alkyl carboxylic acids, thereby highly increasing the rate of protolyses of trialkyl boranes. These reactions may, for example, be utilized for the borylation of H-acidic compounds or for the dehydration of salts.

Abstract: A process for the recovery of oxides of sulfur from combustion waste gases, which comprises cooling said waste gases and forming entrained particles of sodium compounds, consisting essentially of sodium carbonate, by spray contact with sodium hydroxide or sodium carbonate, converting sodium carbonate in the particles to sodium sulfate by passing said oxides of sulphur containing waste gases and said sodium compound particles over plate-like packings, whereby said particles are comminuted to a finer particle size form so as to enhance the reaction of said sulfate particles with the oxides of sulfur in said waste gases, collecting entrained particles of said sodium compounds in a dust collector.

Abstract: A process for recovery of iodine from waste containing iodine or iodine compound, comprising the steps of burning the waste in a cumbustion chamber, and scrubbing out the iodine or iodine compound in the resulting combustion gas with a basic aqueous solution of sodium thiosulfate.

Abstract: A process for the fluorination of carboxylate compounds to the corresponding acyl fluoride or carbamoyl fluoride, the latter compounds decompose to isocyanates and hydrogen fluoride, wherein the carboxylic acid, its anhydride or metal salt is intimately mixed with a metal fluorosulfonate and heated at a temperature at which the gaseous carboxylic acid fluoride is formed or decomposed.

Abstract: Ferric sulfate obtained by the oxidation of ferrous sulfate or ferric sulfate available in its original state is added to an alkali hydroxide at a ratio such that the amount of said alkali hydroxide will be in excess of its stoichiometric proportion, so as to form a pasty substance. Then, this pasty substance is subjected to a hydrothermal treatment. From the resultant product of the treatment, there are obtained micaceous .alpha.-iron oxide crystals and aqueous solutions of sodium sulfate and alkali hydroxide.

Abstract: A method for processing alunite consisting in that alunite ore is treated with a solution of caustic alkalis at a maximum temperature of 60.degree.C, and a solid residue resulting from the above operation and containing largely potassium and sodium sulphates, is washed with hot water. As a result, potassium and sodium sulphates are dissolved in the wash water, and potassium sulphate is isolated by the action of a caustic-potash solution. The method enables losses of alkalis and aluminium during processing alunite ores containing active forms of silicon compounds to be much reduced, which compound when treating alunite ores with a solution of caustic alkalis, are liable to form insoluble aluminosilicates which are discarded into slime and thus lost together therewith when the latter is separated from the process solution.

Abstract: Metal salts which are crystallizable from a saturated aqueous solution of the salt in the presence of a dispersion of polytetrafluoroethylene (hereinafter referred to as PTFE) resin are grown as geometrically better defined and larger crystals than those grown from an unseeded saturated solution.

Abstract: Chrome saltcake has stable free flowing properties imparted to it by subjecting the sodium dichromate impurity present in chrome saltcake to reaction to form a product that is less susceptible to absorption of moisture than sodium dichromate.

Abstract: Pigment TiO.sub.2 is prepared from sodium titanate by mixing with sulfuric acid, calcining at from 600.degree. to above about 900.degree.C, thereafter quenching in water, dissolving out the soluble sodium sulfate and recovering TiO.sub.2. By operating at 900.degree.C and above, artificial rutile is obtained. Instead of sulfuric acid, other mineral acids, their anhydrides, ammonium and alkali metal acid salts of said acids and borax may be employed.

Abstract: A method and apparatus for removing sulfur oxides from flue gas comprise cooling and conditioning the hot flue gas to increase the degree of water vapor saturation prior to passage through a bed of substantially dry carbonate chips or lumps, e.g., crushed limestone. The reaction products form as a thick layer of sulfites and sulfates on the surface of the chips which is easily removed by agitation to restore the reactive surface of the chips.

Abstract: Metal, e.g. sodium sulfate, is separated from metal, e.g. sodium sulfite, in a solution, for instance a solution used in a system involving contact of sulfur dioxide-containing gases with the sodium sulfite solution as an absorbing solution to recover sulfur dioxide wherein the absorbing solution is regenerated after contact with the gas and recycled for further use. A portion of the absorbing solution is purged to avoid the unduly large build-up of sodium sulfate in it. The purge stream is contacted with sulfur dioxide to reduce the amount of sodium sulfite therein to relatively soluble sodium bisulfite, and the relatively insoluble sodium sulfate is recovered therefrom as undissolved solids. The liquid separated from the sodium sulfate, which is rich in sodium bisulfite, is returned to the absorbing solution. In a preferred aspect, the purge stream is withdrawn from the absorbing solution subsequent to contact with the sulfur dioxide-containing gases and before regeneration.

Abstract: Evaporite minerals comprising mixtures of relatively coarse salts are treated in a manner such that certain of said salts are converted by recrystallization to very finely divided form and then separated from the coarse salts by size classification such as elutriation, the treatment being especially useful in a process for the recovery of potassium sulfate from marine evaporite mixtures such as kainite and halite.

Abstract: A water-insoluble exchange agent is used to remove barium from aqueous barium sulfide and then to release the barium to aqueous alkali, forming an aqueous solution from which there is crystallized substantially pure Ba(OH).sub.2, 8H.sub.2 O, particularly useful as an ingredient of "barium greases". The preferred exchange agent is di(2-ethylhexyl)phosphoric acid, which can be regenerated and recycled.

Abstract: A solution of sodium sulfite or sulfide is reacted with ammonium sulfate, so as to produce a gas containing SO.sub.2 or H.sub.2 S, NH.sub.3 and H.sub.2 O, which is thereafter treated for sulfur production and NH.sub.3 recovery, and a liquid outflow containing sodium sulfate which is reacted with CO.sub.2 and NH.sub.3, in order to produce NaHCO.sub.3 and regenerate the ammonium sulfate. NaHCO.sub.3 may be converted to sodium carbonate and CO.sub.2, the latter being re-used in the process.

Abstract: A dry alkaline earth metal silicate or an alkali metal silicate is reacted with an acid hydrogen containing salt to form silico-formic acid.

Abstract: A dry alkaline earth metal silicate or an alkali metal silicate is reacted with a concentrated mineral acid, forming a white granular mixture. The mineral acid is then neutralized with a dry alkali metal carbonate or hydroxide producing monosilanal and monosilanic acid. Monosilanal will react with water to produce monosilandiol.

Abstract: A process is described for the removal of oxides of sulfur, dust and mist from a combustion waste gas such as the waste gas evolved from a glass melting furnace in which the waste gas is contacted with an absorbing solution containing an alkaline absorbent such as NaOH, Na.sub.2 CO.sub.3 or Na.sub.2 SO.sub.3, whereby the oxides of sulfur are absorbed and the temperature of the waste gas is decreased and the humidity of the waste gas in increased. The treated waste gas is then passed through a glass fiber filter which is maintained under moist conditions in order to efficiently remove dust and mist particles from the waste gas. Crystalline sodium sulfate hydrate is recovered from the absorbing solution contacted with the waste gas.

Abstract: A method for the reprocessing of cell liquor from diaphragm cell electrolysis plants that operate on potassium chloride brine. The cell liquor is contacted with an SO.sub.2 -bearing gas, and the effluent solution is oxidized with an oxygen-bearing gas, then a definite quantity of KCl is added to said oxidized solution, and this solution is subjected to a filtration and precipitation step, and finally it is then recycled as make-up brine to the electrolysis cell plant.