Dowex-50 X8 100-200 resin column of Interfering anions were precalculated capacity. removed by elution volumes of distilled water. with two-column The resin was then stripped of cations with three-column volumes of 2N) HCl and the neutralized to methyl orange with NH4OH. concentrated eluate Cal- cium was removed by precipitation with ammonium oxalate followed by boiling and filtration. with 1N The filtrate was made basic NH4gOH; 5 per cent (NH4)2 POqg cipitate formed, was added until a pre- and an excess of NH4OH was then added while stirring constantly. The precipitate, magnesium ammonium phos- phate, was allowed to settle overnight, removed by filtering, dissolved in 6 drops of concentrated H2SO0, and made to volume with water. Magnesium was determined by titrating an aliquot of this solution against a standard EDTA solution in which Eriochrome Black T was used as the indicator. Total phosphorous was determined method of Fleischer et al. (1958). the colorimetric The ash was converted to the nitrate form and diluted with water. reagent by The colorimetric consisted of aqueous solution of 2.5 per cent ammo- nium molybdate, 1 per cent bismuth subcarbonate in 7N HjS04 and crystals of ascorbic acid. Color transmittance at 660 millimicrons was read on a Bausch and Lomb "Spectronic 20" colorimeter and compared against a known standard.