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YS/T 1028.1-2015 (YS/T1028.1-2015)

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Standards related to: YS/T 1028.1-2015

YS/T 1028.1-2015: PDF in English (YST 1028.1-2015)

YS/T 1028.1-2015
YS
NON-FERROUS METAL INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 77.120.99
H 71
Methods for chemical analysis of lithium iron phosphate -
Part 1: Determination of total iron content - Titanium
trichloride reduction potassium dichromate titration
methods
ISSUED ON: APRIL 30, 2015
IMPLEMENTED ON: OCTOBER 01, 2015
Issued by: Ministry of Industry and Information Technology of PRC
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Summary of method ... 4
3 Reagents and materials ... 4
4 Specimens ... 5
5 Analytical procedures ... 5
6 Calculation of analysis results ... 6
7 Precision ... 6
8 Test report ... 7
Methods for chemical analysis of lithium iron phosphate -
Part 1: Determination of total iron content - Titanium
trichloride reduction potassium dichromate titration
methods
1 Scope
This Part of YS/T 1028 specifies the method for the determination of total iron in
lithium iron phosphate.
This section applies to the determination of total iron in lithium iron phosphate. The
measuring range is: 28% ~ 36%.
2 Summary of method
After the sample is dissolved in hydrochloric acid, sodium tungstate is used as an
indicator; a small amount of ferric iron is reduced to ferrous iron with titanium
trichloride, to form "tungsten blue"; the excess trivalent titanium is naturally oxidized
by the oxygen in the air. In the sulfuric acid-phosphoric acid medium, sodium
diphenylamine sulfonate is used as an indicator, to titrate the divalent iron by the use of
potassium dichromate standard solution.
3 Reagents and materials
3.1 Hydrochloric acid (1 + 1).
3.2 Sulfuric acid-phosphoric acid mixed solution: Slowly add 15 mL of sulfuric acid (ρ
≈ 1.84 g/mL) to 70 mL of water. After cooling, add 15 mL of phosphoric acid (ρ≈
1.69 g/mL). Mix well.
3.3 Titanium trichloride solution (1 + 14): Take 2 mL of titanium trichloride solution
(about 15% titanium trichloride solution). Use hydrochloric acid (1 + 5), to dilute it to
30 mL.
3.4 Potassium dichromate standard titration solution [c( ) = 0.0500 mol/L]:
Weigh 2.4516 g of standard potassium dichromate (after predried at 140 °C ~ 150 °C
for 2 h, place it in a desiccator and cool to room temperature). After dissolving in water,
transfer it into a 1000 mL volumetric flask. Use water to dilute it to the mark. Mix well.
3.5 Sodium tungstate indicator solution (250 g/L): Weigh 25 g of sodium tungstate and
dissolve it in an appropriate amount of water. Add 5 mL of phosphoric acid. Use water
to dilute it to 100 mL. Mix well.
3.6 Sodium diphenylamine sulfonate indicator solution (5 g/L): Weigh 0.50 g of sodium
diphenylamine sulfonate. Dissolve it in water. Use water to dilute it to 100 mL. Mix
well. Store in a brown bottle.
4 Specimens
The particle size of the specimen shall not be greater than 0.10 mm.
5 Analytical procedures
5.1 Sample
Weigh 4.00 g of specimen, accurate to 0.0001 g.
5.2 Number of measurements
Carry out two independent measurements. Take the average value.
5.3 Blank test
Do a blank test with the sample.
5.4 Determination
5.4.1 Put the sample (5.1) in a 250 mL beaker. Add 40 mL of hydrochloric acid (3.1).
Cover a watch glass. Heat in a fume hood at low temperature to a slight boil, for 3 min
~ 5 min. Use a small amount of water, to rinse the watch glass. After cooling, use filter
paper to filter it. Use water to wash the filter residue 5 ~ 7 times. Receive the filtrate in
a 250 mL volumetric flask. Use water to dilute it to the mark. Shake well.
5.4.2 Pipette 25.00 mL of test solution (5.4.1) into a 250 mL conical flask. Add 1 mL
of sodium tungstate indicator solution (3.5). Dropwise add titanium trichloride solution
(3.3) to the test solution, under constant shaking, until a steady blue color appears. Wait
until the blue color disappears.
5.4.3 Immediately add 20 mL of sulfuric acid-phosphoric acid mixed solution (3.2).
Add 4 drops of sodium diphenylamine sulfonate indicator solution (3.6). Use potassium
dichromate standard titration solution (3.4), to titrate it, until the solution turns purple
and does not disappear for 30 seconds, which is the end.
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.