The author's method for the separation of lithium from the other alkali metals has been studied with the view to its adaptability to the separation of magnesium from these metals. With some modifications, the procedure has been found to be well adapted to magnesium. The method depends on the pogressive precipitation of the sodium and potassium chlorides €ram a concentrated aqueous solution by the use of alcohol and ether and is divided into 2 stages, (I) in which all but a few mg. is precipitated, and (2) in which the last few mg. is removed from solution. The method has several advantages, viz., (I) it affords a direct determination of the sodium and potassium chlorides in that they are precipitated jirst (rather than after magnesium as in other methods), (2) the reagents used are readily volatile organic solvents, and (3) no foreign base or salts is introduced as a precipitating agent.