Process for the production of surfactant mixtures based on ether sulfonates and their use

The process of recovering oil from an oil reservoir, comprising preparing a surfactant mixture consisting essentially of an alkyl ether sulfonic acid or salt thereof as a principal constituent and at most a substantially equal quantity of alkoxylated alcohol as a by-product of the process by reacting an alkyl ether sulfate with an aqueous alkali metal sulfite solution at a temperature of from about 160.degree. C. to about 220.degree. C. a pH of from about 7.5 to about 10, and under a pressure of up to about 20 bar, wherein said alkali metal sulfite is present in a stoichiometric excess with respect to said alkyl ether sulfate, and wherein said alkyl ether sulfate is added to said aqueous alkali metal sulfite solution with simultaneous mixing at a rate so that about 20% of the total reaction time is taken up by the addition of said alkyl ether sulfate, and extracting the surfactant mixture formed with a substantially water-insoluble alcohol at a temperature of from about 50.degree. C. to about 100.degree. C. whereby said surfactant mixture is substantially free from sulfate salt, and flooding said oil reservoir with said surfactant mixture.