has been replaced by Practice E1601. The reproducibility, R2,
of Practice E173 corresponds to the reproducibility index Rof
Practice E1601. The repeatability, R1, of Practice E173 corre-
sponds to the repeatability index, r, of Practice E1601.
8.2 Rounding of test results obtained using this test method
shall be performed as directed in ASTM E29, Rounding
Method, unless an alternative rounding method is specified by
the customer or applicable material specification.
MANGANESE BY THE META PERIODATE
SPECTROPHOTOMETRIC METHOD
9. Scope
9.1 This method covers the determination of manganese
from 0.01 % to 5.00 %.
10. Summary of Method
10.1 Manganous ions are oxidized to permanganate ions by
treatment with periodate. Tungsten when present at composi-
tions greater than 0.5 % is kept in solution with H
3
PO
4
.
Solutions of the samples are fumed with HClO
4
so that the
effect of periodate is limited to the oxidation of manganese.
Spectrophotometric absorbance measurement is made at 545
nm.
11. Concentration Range
11.1 The recommended concentration range is 0.15 mg to
0.8 mg of manganese per 50 mL of solution, using a 1-cm cell
(see Note 1) and a spectrophotometer with a band width of 10
nm or less.
NOTE 1—This method has been written for cells having a 1-cm light
path and a “narrow-band” instrument. The concentration range depends
upon band width and spectral region used as well as cell optical path
length. Cells having other dimensions may be used, provided suitable
adjustments can be made in the amounts of sample and reagents used.
12. Stability of Color
12.1 The color is stable for at least 24 h.
13. Interferences
13.1 HClO
4
treatment, which is used in the procedure,
yields solutions which can be highly colored due to the
presence of Cr (VI) ions. Although these ions and other colored
ions in the sample solution undergo no further change in color
quality upon treatment with metaperiodate ion, the following
precautions must be observed when filter spectrophotometers
are used: Select a filter with maximum transmittance between
545 nm and 565 nm. The filter must transmit not more than 5 %
of its maximum at a wavelength shorter than 530 nm. The band
width of the filter should be less than 30 nm when measured at
50 % of its maximum transmittance. Similar restrictions apply
with respect to the wavelength region employed when other
“wide-band” instruments are used.
13.2 The spectral transmittance curve of permanganate ions
exhibits two useful minima, one at approximately 526 nm, and
the other at 545 nm. The latter is recommended when a
“narrow-band” spectrophotometer is used.
13.3 Tungsten, when present in amounts of more than 0.5 %
interferes by producing a turbidity in the final solution. A
special procedure is provided for use with samples containing
more than 0.5 % tungsten which eliminates the problem by
preventing the precipitation of the tungsten.
14. Reagents
14.1 Manganese, Standard Solution (1 mL = 0.032 mg
Mn)—Transfer the equivalent of 0.4000 g of assayed, high-
purity manganese (purity: 99.99 % minimum), to a 500-mL
volumetric flask and dissolve in 20 mL of HNO
3
by heating.
Cool, dilute to volume, and mix. Using a pipet, transfer 20 mL
to a 500-mL volumetric flask, dilute to volume, and mix.
14.2 Nitric-Phosphoric Acid Mixture—Cautiously, while
stirring, add 100 mL of HNO
3
and 400 mL of H
3
PO
4
to 400
mL of water. Cool, dilute to 1 L, and mix. Prepare fresh as
needed.
14.3 Potassium Metaperiodate Solution (7.5 g/L)—Dissolve
7.5 g of potassium metaperiodate (KIO
4
) in 200 mL of hot
HNO
3
(1 + 1), add 400 mL of H
3
PO
4
, cool, dilute to 1 L, and
mix.
14.4 Water, Pretreated with Metaperiodate—Add 20 mL of
KIO
4
solution to 1 L of water, mix, heat at not less than 90°C
for 20 min to 30 min, and cool. Use this water to dilute
solutions to volume that have been treated with KIO
4
solution
to oxidize manganese, and thus avoid reduction of permangan-
ate ions by any reducing agents in the untreated water.
Caution—Avoid the use of this water for other purposes.
15. Preparation of Calibration Curve
15.1 Calibration Solutions—Using pipets, transfer 5 mL, 10
mL, 15 mL, 20 mL, and 25 mL of manganese standard solution
(1 mL = 0.032 mg Mn) to 50-mL borosilicate glass volumetric
flasks, and if necessary, dilute to approximately 25 mL.
Proceed as directed in 15.3.
15.2 Reference Solution—Transfer approximately 25 mL of
water to a 50-mL borosilicate glass volumetric flask. Proceed
as directed in 15.3.
15.3 Color Development—Add 10 mL of KIO
4
solution,
and heat the solutions at not less than 90°C for 20 min to 30
min (Note 2). Cool, dilute to volume with pretreated water, and
mix.
NOTE 2—Immersing the flasks in a boiling water bath is a preferred
means of heating them for the specified period to ensure complete color
development.
15.4 Spectrophotometry:
15.4.1 Multiple-Cell Spectrophotometer—Measure the cell
correction using the Reference Solution (15.2) in absorption
cells with a 1-cm light path and using a light band centered at
545 nm. Using the test cell, take the spectrophotometric
absorbance readings of the calibration solutions versus the
Reference Solution (15.2).
15.4.2 Single-Cell Spectrophotometer—Transfer a suitable
portion of the Reference Solution (15.2) to an absorption cell
with a 1-cm light path and adjust the spectrophotometer to the
initial setting, using a light band centered at 545 nm. While
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3