GB1033030A - Preparation of inorganic and organic salts - Google Patents

Abstract

A metal or ammonium salt of an acid HX which has a dissociation constant higher than 1 x 10-6 is prepared by reacting either HX in the presence of a water-insoluble weak base anion exchanger, or said anion exchanger in the form of a salt with HX, with a metal or ammonium salt of an acid HY, HY having a dissociation constant greater than that of HX. Specified acids HX are sulphurous and phosphoric acids, the metal salts of HY may be sodium chloride, nitrate or sulphate and other specified metal ions are Li, K and Cs. The anion exchanger may be a liquid amine containing 8-25 carbon atoms, and may be a tert.-alkyl primary amine, a secondary amine or a tertiary amine. Such liquid amines are preferably dissolved in an inert water-insoluble solvent, e.g. a hydrocarbon such as kerosene, in the concentration range 5-50%. Less desirably, solid anion exchangers, e.g. those prepared by chloromethylating and aminating a cross-linked aryl hydrocarbon polymer, particularly copolymers of styrene and divinyl benzene, or those prepared by the aminolysis of a cross-linked alkyl acrylate polymer, may be used. Sodium bisulphite may be prepared by agitating an aqueous solution of NaCl with a solvent solution of the amine present in e.g. 33% molar excess and bubbling SO2 through the mixture. The bisulphite may be recovered from the aqueous phase by evaporation, or converted to sodium sulphite by contacting the solution with the free base form of the amine. Sodium dihydrogen phosphate may be prepared by equilibrating phosphoric acid in, e.g., 30% solution with a 33% molar excess of amine and added the stoichiometric quantity of NaCl, or the three reagents may be mixed together. Partial conversion of NaH2PO4 to Na2HPO4 may be achieved by the process of the invention. The anion exchanger may be regenerated with sodium carbonate, sodium hydroxide or ammonia or, particularly in the case of the liquid resins, with an aqueous suspension of lime.ALSO:A metal or ammonium salt of an acid HX which has a dissociation constant higher than 1 x 10-6 is prepared by reacting either HX in the presence of a water-insoluble weak base anion exchanger, or said anion exchanger in the form of a salt with HX, with a metal or ammonium salt of an acid Hy, the dissociation constant of Hy being higher than that of HX. Examples describe the preparation of sodium acid tartrate, sodium citrate, sodium acid malate, sodium formate, sodium acetate and sodium succinate from stoichiometric amounts of sodium chloride solution and the appropriate acid using a 33% molar excess of the anion exchanger. Other metal salts of Hy may be sodium nitrate or sulphate. Other specified metal ions are Li, K and Cs. The anion exchanger may be a liquid amine having 8-25 carbon atoms, and may be a tert.-alkyl primary amine, or a secondary amine, or a tertiary amine. Such liquid amines are preferably dissolved in an inert water-insoluble solvent, e.g. a hydrocarbon such as kerosene, in a concentration of 5-50%. Less desirably solid anion exchangers may be used, e.g. those prepared by chloromethylating and aminating a cross-linked aryl hydrocarbon polymer particularly co-polymers of styrene and divinylbenzene, or those prepared by the aminolysis of a crosslinked alkyl acrylate polymer. The exchangers may be regenerated with sodium carbonate, sodium hydroxide, ammonia or, particularly in the case of the liquid exchangers, an aqueous suspension of lime.