PREPARATION OF PURE AQUEOUS BETAINE SOLUTION

The process described relates to the preparation of aqueous betaine solutions by reacting a tertiary amine with an omega -monohalocarboxylic acid, preferably monochloroacetic acid, and alkali metal hydroxide in the presence of water, it being intended that these betaine solutions are ultra pure especially with regard to tertiary starting amine and omega -monohalocarboxylic acid. This is achieved by reacting the three reactants initially at a certain molar ratio with the aim of obtaining a betaine solution which only contains a tolerated amount of starting amine. This aqueous betaine solution is then treated with a sulphonating agent, preferably an alkali metal sulphite, alkali metal pyrosulphite or alkali metal bisulphite for converting the omega -monohalocarboxylic acid which is present into the corresponding sulphocarboxylic acid which is not troublesome. The process described is simple to carry out and results in the abovementioned ultra pure aqueous betaine solutions.