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.