The present invention relates to a method for purifying phosphoric acid from a mixture which comprises organic compounds and water. In particular the present invention relates to a method for purifying phosphoric acid from a pulping slurry, containing or consisting of phosphoric acid, one or more organic compounds and water, comprising or consisting of the following steps: i) providing a mixture containing or consisting of phosphoric acid, one or more substance(s) S having at least one secondary carbon atom attached to an alkoxy group, one or more (further) organic compounds and water, and adjusting (if necessary) the molar ratio of phosphoric acid to the total of one or more substance(s) S, having at least one secondary carbon atom attached to an alkoxy group, in the mixture to be in the range of from 1:0.4 to 1:10, preferably to be in the range of approximately 1:0.6 to 1:4, especially preferably to be approximately 1:0.85 to 1:2, ii) heating the mixture to 25° C. or more until phase separation occurs, iii) removing the light phase, and iv) separating the phosphoric acid from the heavy phase.