Abstract: A method for the synthesis of betaines of the general formula ##STR1## by quaternizing the fatty acid amide dialkylamines of the general formula ##STR2## with .omega.-halogenalkylcarboxylic acids of the formula X-(CH.sub.2).sub.y COOH, wherein X is a halogen group, or their salts in aqueous solution, the reaction being carried out within a temperature range of 115.degree. to 180.degree. C., until organically bound chlorine can no longer be detected, the fatty acid amide dialkylamine optionally being quaternized partially or completely in a first step at 80.degree. to 100.degree. C.

Abstract: An aqueous liquid solution of a betaine of the following general formula is disclosed ##STR1## in which R is an alkyl group of coconut fatty acids, preferably hydrogenated coconut fatty acids, or a fatty acid mixture which, on the average, corresponds to coconut fatty acids, wherein the solution has a solids content of at least 40% by weight, a pH of 5 to 8 and an aminoamide content of not more than 1% by weight, characterized by a content of 1 to 3% by weight, based on the solution, of one or more saturated fatty acids with, on the average, 8 to 18 carbon atoms or one or more unsaturated fatty acids with, on the average, 8 to 24 carbon atoms and 0 to 4% by weight of glycerin, based on the solution.