662 Dinwiddle — Separation of Magnesium. 



Art. XLIX. — The Separation of Magnesium from Lithium 

 by Means of Ammonium Carbonate in Alcoholic Solution ; 

 by J. Gray Dinwiddie. 



(Contributions from the Kent Chemical Laboratory of Yale Univ.— cclxvii.) 



The following work was undertaken to determine the con- 

 ditions under which lithium may be separated quantitatively 

 from magnesium by means of ammonium carbonate in alcoholic 

 solution. It has been shown* that by the agency of such a 

 solution magnesium may be separated quantitatively from 

 sodium and potassium andf that very small amounts of 

 magnesium may be detected qualitatively in presence of limited 

 amounts (100 mgm.) of lithium. In the quantitative procedure, 

 the solution containing the salts of magnesium, sodium, and 

 potassium is brought to a volume of about 50 cm3 , an equal 

 amount of absolute alcohol is added, precipitation is made by 

 addition of 50 cm3 of a saturated ammoniacal solution of 

 ammonium carbonate in 50 per cent alcohol, and the mixture 

 is allowed to stand half an hour after stirring vigorously for 

 five minutes. If the amount of alkali salt present is small, the 

 precipitate may be collected without further treatment upon 

 asbestos in the perforated crucible, washed with the precipitant, 

 dried, ignited, and weighed as magnesium oxide. When the 

 amount of alkali salt is large the precipitate may be freed from 

 included alkali salt by decanting the supernatant liquid through 

 the prepared asbestos filter, dissolving the precipitate in hydro- 

 chloric acid and reprecipitating by ammonium magnesium car- 

 bonate as at first. This second precipitate, collected upon the 

 filter used in the decantation, leaves upon ignition a practically 

 pure magnesium oxide. The essential condition of this process 

 is that precipitation shall be brought about by a considerable 

 excess of ammonium carbonate in a 50 per cent alcoholic 

 solution. 



In the work to be described, it was convenient to make use 

 of 93 per cent alcohol instead of absolute alcohol in making up 

 the solution to be treated and the precipitant, but the propor- 

 tions of solution and precipitant were so adjusted that the liquid 

 at the time of precipitation should be 50 per cent alcohol. 



The alcoholic solution of ammonium carbonate was made by 

 mixing 1500 cm3 of the saturated aqueous solution of that reagent 

 with 360 cm3 of concentrated ammonium hydroxide and 1900 cm3 

 of 93 per cent alcohol, settling out the precipitated ammonium 

 carbonate, and filtering off the clear solution. In carrying out 



*Gooch and Eddy, this Journal (4), xxv, 444, 1908. 



f A System of Qualitative Analysis for the Common Elements, Noyes and 

 Bray : reprint from The Technology Quarterly, xxii, p. 472. 



