Abstract: The specific feature of the present method is that in the process solution resulting in the processing of alunite with the object of producing alumina and potassium sulphate therefrom, an excess amount of sodium ions is maintained with respect to the potassium ions.The method is advantageous in that it ensures a higher yield of potassium sulphate and a lower contamination of the final products with respect to sodium and potassium ions.

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 In a preferred aspect, the purge stream is withdrawn from the absorbing solution subsequent to contact with the sulfur dioxide-containing gases and before regeneration.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: 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.