Magnesium oxalate may be quantitatively precipitated in a dense and coarsely crystalline form from 85per thousand acetic acid solution by the gradual release of oxalate ion in this medium as the result of the slow decomposition of dissolved ethyl oxalate. In contrast to a precipitate obtained by the direct addition oxalate ion, one obtained by this technique may be filtered off and washed rapidly. By the use of this special technique of precipitation, the indirect method for the determination of magnesium based upon the solution of magnesium oxalate dilute sulfuric acid and titration of the released oxalic acid becomes a very convenient and simple procedure.