Process for preparing a solution L 1 <115> of an alkali metal alkoxide XOR in the alcohol ROH in an electrolysis cell E <100>, wherein E <100> comprises at least one anode chamber K A <101>, at least one cathode chamber K K <102> and at least one interposed middle chamber K M <103>, wherein K A <101> comprises an anodic electrode E A <104> and a drain A KA <106>, wherein K K <102> comprises a cathodic electrode E K <105>, a feed Z KK <107> and a drain A KK <109>, wherein K M <103> comprises a feed Z KM <108>, a gas inlet G E <122> and a gas outlet G A <120>, is separated from K A <101> by a diffusion barrier D <110> and is separated from K K <102> by an alkali metal cation-conducting solid-state electrolyte F K <111>, wherein K M <103> and K A <101> are connected to one another by a connection V AM <112> through which liquid can be routed from K M <103> into K A <101>, wherein the process comprises the following steps (a), (b), (c) and (d) that proceed simultaneously: (a) a solution L 2 <113> comprising the alcohol ROH is routed through K K <102>, (b) a neutral or alkaline, aqueous solution L 3 <114> of a salt S comprising X as cation is routed through K M, then via V AM, then through K A <101>, (c) voltage is applied between E A <104> and E K <105>, (d) a gas I <121> is routed via the gas inlet G E <122> into the solution L 3 <114> in the middle chamber K M <103>, and removed via the gas outlet G A <120> from the middle chamber K M <103>, which affords the solution L 1 <115> at the drain A KK <109>, with a higher concentration of XOR in L 1 <115> than in L 2 <113>, and which affords an aqueous solution L 4 <116> of S at the drain A KA <106>, with a lower concentration of S in L 4 <116> than in L 3 <114>, wherein X is an alkali metal cation and R is an alkyl radical having 1 to 4 carbon atoms. wherein E <100> comprises at least one anode chamber K A <101>, at least one cathode chamber K K <102> and at least one interposed middle chamber K M <103>, wherein K A <101> comprises an anodic electrode E A <104> and a drain A KA <106>, wherein K K <102> comprises a cathodic electrode E K <105>, a feed Z KK <107> and a drain A KK <109>, wherein K M <103> comprises a feed Z KM <108>, a gas inlet G E <122> and a gas outlet G A <120>, is separated from K A <101> by a diffusion barrier D <110> and is separated from K K <102> by an alkali metal cation-conducting solid-state electrolyte F K <111>, wherein K M <103> and K A <101> are connected to one another by a connection V AM <112> through which liquid can be routed from K M <103> into K A <101>, wherein the process comprises the following steps (a), (b), (c) and (d) that proceed simultaneously: (a) a solution L 2 <113> comprising the alcohol ROH is routed through K K <102>, (b) a neutral or alkaline, aqueous solution L 3 <114> of a salt S comprising X as cation is routed through K M, then via V AM, then through K A <101>, (c) voltage is applied between E A <104> and E K <105>, (d) a gas I <121> is routed via the gas inlet G E <122> into the solution L 3 <114> in the middle chamber K M <103>, and removed via the gas outlet G A <120> from the middle chamber K M <103>, (a) a solution L 2 <113> comprising the alcohol ROH is routed through K K <102>, (b) a neutral or alkaline, aqueous solution L 3 <114> of a salt S comprising X as cation is routed through K M, then via V AM, then through K A <101>, (c) voltage is applied between E A <104> and E K <105>, (d) a gas I <121> is routed via the gas inlet G E <122> into the solution L 3 <114> in the middle chamber K M <103>, and removed via the gas outlet G A <120> from the middle chamber K M <103>, which affords the solution L 1 <115> at the drain A KK <109>, with a higher concentration of XOR in L 1 <115> than in L 2 <113>, and which affords an aqueous solution L 4 <116> of S at the drain A KA <106>, with a lower concentration of S in L 4 <116> than in L 3 <114>, wherein X is an alkali metal cation and R is an alkyl radical having 1 to 4 carbon atoms.