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GB/T 4698.8-2017: Methods for chemical analysis of titanium sponge, titanium and titanium alloys -- Part 8: Determination of aluminum content -- Separation with sodium hydroxide-EDTA complex-metric titration and inductively coupled plasma atomic emission spectrometry
GB/T 4698.8-2017
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.120.50
H 14
Replacing GB/T 4698.8-1996
Methods for chemical analysis of titanium sponge,
titanium and titanium alloys - Part 8: Determination of
aluminum content - Separation with sodium hydroxide
- EDTA complex-metric titration and inductively
coupled plasma atomic emission spectrometry
ISSUED ON: SEPTEMBER 29, 2017
IMPLEMENTED ON: APRIL 01, 2018
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 6 
2 Method One - Alkali separation - EDTA complexometric titration ... 6 
3 Method Two -- Inductively coupled plasma atomic emission spectrometry . 11 
4 Test report ... 14 
Methods for chemical analysis of titanium sponge,
titanium and titanium alloys - Part 8: Determination of
aluminum content - Separation with sodium hydroxide
- EDTA complex-metric titration and inductively
coupled plasma atomic emission spectrometry
1 Scope
This Part of GB/T 4698 specifies the methods to determine aluminum content
in sponge titanium, titanium and titanium alloys.
This Part is applicable to the determination of aluminum content in sponge
titanium, titanium and titanium alloys. The determination range: 0.80%~8.50%
for Method One; 0.010%~8.50% for Method Two. When the determination
ranges overlap, Method One is the arbitration analysis method.
2 Method One - Alkali separation - EDTA
complexometric titration
2.1 Method summary
The test material is dissolved with sulfuric acid. Separate the elements such as
titanium, iron, chromium, zirconium, copper, manganese and part of vanadium
by sodium hydroxide precipitation. In a weakly acidic medium of pH5, add EDTA
complex aluminum. Use zinc acetate standard titration solution to titrate
excessive EDTA. Add potassium fluoride to complex aluminum and release
quantitative EDTA. Then use zinc acetate standard titration solution to titrate
EDTA released, so as to obtain the aluminum content.
For tin interference determination, add potassium iodide to volatilize to remove.
Vanadium affects the judgment of the end point of titration. Add hydroxylamine
hydrochloride to eliminate its interference.
2.2 Reagents
Unless otherwise stated, only the confirmed analytically-pure reagents and
laboratory grade two water are used in the analysis.
2.2.1 Nitric acid (ρ=1.42g/mL).
2.2.2 Sulfuric acid (1+1).
2.2.3 Hydrochloric acid (1+1).
2.2.4 Potassium iodide solution (200g/L).
2.2.5 Ferric chloride solution (50g/L): Weigh 5g of iron trichloride (FeCl3·6H2O)
and dissolve it in 100mL of hydrochloric acid (1+99).
2.2.6 Sodium hydroxide solution (300g/L).
2.2.7 Sodium hydroxide solution (150g/L).
2.2.8 Copper chloride solution (10g/L): Weigh 1g of copper chloride
(CuCl2·2H2O) and dissolve it in 100mL of water.
2.2.9 Hydroxylamine hydrochloride solution (100g/L).
2.2.10 Disodium ethylenediaminetetraacetic acid (Na2EDTA) solution
[c(Na2EDTA)]=0.05mol/L]: Weigh 18.6g of Na2EDTA (C10H14N2O8Na2·2H2O)
into a 500mL beaker. Add 300mL of water to dissolve. Transfer to a 1000mL
volumetric flask. Use water to dilute to the scale mark. Mix well.
2.2.11 Hexamethylenetetramine buffer solution (pH5): Weigh 150g of
hexamethylenetetramine in a 1000mL beaker. Add 400mL of water to dissolve.
Add about 50mL of hydrochloric acid (ρ=1.19g/mL) to adjust the solution to
about pH 5 (check with pH test paper). Use water to dilute to 500mL. Mix well.
2.2.12 Potassium fluoride solution (200g/L): Stored in plastic bottles.
2.2.13 Aluminum standard storage solution: Weigh 1.0000g of metallic
aluminum (wAl≥99.99%) into a 300mL beaker. Add 20mL of sodium hydroxide
solution (2.2.6). After the violent reaction stops, heat to dissolve. Remove it and
cool. Add hydrochloric acid (2.2.3) until the precipitated precipitate is dissolved
with an excess of 20mL. Cool. Transfer to a 1000mL volumetric flask. Use water
to dilute to the scale mark. Mix well. 1mL of this solution contains 1.0mg of
aluminum.
2.2.14 Standard titration solution of zinc acetate [c(Zn2+)≈0.014mol/L].
2.2.14.1 Preparation: Weigh 3g of zinc acetate [Zn(CH3COO)2·2H2O] into a
200mL beaker. Add 50mL of water to dissolve. Add 2mL of glacial acetic acid
(ρ=1.05g/mL). Transfer to a 1000mL volumetric flask. Use water to dilute to the
scale mark. Mix well.
2.2.14.2 Calibration: Pipette three portions of 5.00mL of aluminum standard
3.2.3 Nitric acid (ρ=1.42g/mL).
3.2.4 Titanium (wTi≥99.9%, wAl< 0.005%).
3.2.5 Aluminum standard storage solution: Weigh 1.0000g of metallic aluminum
(wAi≥99.99%) into a 300mL beaker. Add 20mL of sodium hydroxide solution
(300g/L). After the violent reaction stops, heat to dissolve. Remove and cool.
Add hydrochloric acid (3.2.1) until the precipitated precipitate is dissolved with
an excess of 20mL. Cool. Transfer to a 1000mL volumetric flask. Use water to
dilute to the scale mark. Mix well. 1mL of this solution contains 1mg of aluminum.
3.2.6 Aluminum standard solution A: Pipette 10.00mL of aluminum standard
stock solution (3.2.5) into a 100mL volumetric flask. Add 5mL of hydrochloric
acid (3.2.1). Use water to dilute to the scale mark. Mix well. 1mL of this solution
contains 100μg of aluminum.
3.2.7 Aluminum standard solution B: Pipette 10.00mL of aluminum standard
solution A (3.2.6) into a 100mL volumetric flask. Add 5mL of hydrochloric acid
(3.2.1). Use water to dilute to the scale mark. Mix well. 1mL of this solution
contains 10μg of aluminum.
3.2.8 Argon (volume fraction≥99.99%).
3.3 Instruments
Inductively coupled plasma atomic emission spectrometer: Equipped with
hydrofluoric acid resistant sampling system, of which the resolution is less than
0.006nm (at 200nm).
3.4 Specimen
Follow the promulgated standards for sample preparation of sponge titanium,
titanium and titanium alloys.
3.5 Analysis steps
3.5.1 Test material
Weigh 0.10g of specimen (3.4), to the nearest of 0.0001g.
3.5.2 Number of determinations
Conduct two determinations independently. Take the average value.
3.5.3 Blank test
Conduct the blank test with test material.
3.5.4 Preparation of analytical test solution
3.5.4.1 Place the test material (3.5.1) in a 100mL PTFE beaker. Blow in a small
amount of water. Add 5mL of hydrochloric acid (3.2.1). Add 1mL of hydrofluoric
acid (3.2.2). Heat at low temperature until the sample is completely dissolved.
Then add 0.5mL of nitric acid (3.2.3) dropwise until the solution is clear.
Continue heating to drive off nitrogen oxides. Remove and cool to room
temperature.
3.5.4.2 Transfer to a 100mL plastic volumetric flask. Use water to dilute to the
scale mark. Mix well.
3.5.5 Preparation of working curve solution
3.5.5.1 Weigh 6 portions of titanium metal (3.2.4) equivalent to the titanium
content of the test material (3.5.1) in a series of 100mL PTFE beakers. Operate
according to 3.5.4.1 along with the test material.
3.5.5.2 Transfer the solution to six 100mL plastic volumetric flasks. Add 0mL,
1.00mL of aluminum standard solution B (3.2.7), 1.00mL of aluminum standard
solution A (3.2.6), 1.00mL, 3.00mL, 6.00mL, 9.00mL of aluminum standard
storage solution (3.2.5) in sequence. Use water to dilute to the scale mark. Mix
well.
3.5.6 Measurement
In the inductively coupled plasma atomic emission spectrometer, at the sel...