GB/T 3051-2000 English PDF (GBT3051-2000)

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GB/T 3051-2000: Inorganic chemical products for industrial use. General method for determination of chloridecontent. Mercurimetric method
GB/T 3051-2000
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.040.40
G 10
neq ISO 5790:1979
Replacing GB/T 3051-1982(1989)
Inorganic chemical products for industrial use - General
method for determination of chloride content -
Mercurimetric method
ISSUED ON: JULY 31, 2000
IMPLEMENTED ON: MARCH 01, 2001
Issued by: State Bureau of Quality and Technical Supervision
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Method summary ... 5 
4 Reagents and materials ... 6 
5 Instruments and equipment ... 8 
6 Analytical procedures ... 8 
7 Presentation of analysis results ... 9 
Appendix A (Normative) The chloride ion content in the test solution and the
concentration of the corresponding standard titration solution ... 10 
Appendix B (Normative) Ions that do not interfere with the determination and ions that
interfere with the determination, as well as their limits ... 11 
Appendix C (Informative) Elimination method of interfering ions ... 13 
Appendix D (Informative) Method for disposing waste liquid ... 16 
Inorganic chemical products for industrial use - General
method for determination of chloride content -
Mercurimetric method
1 Scope
This standard specifies a general method for the determination of chloride content in
inorganic chemical products - Mercurimetric method.
This standard is applicable to specimen, which has a chloride (in terms of C1) content
of 0.01 mg ~ 80 mg. When the concentration of mercury nitrate standard solution used
is less than 0.02 mol/L, the titration shall be carried out in an ethanol-water solution.
The ions K+, Na+, Ca2+, Mg2+, Ba2+, Zn2+, Pb2+, NO3-, CO32-, BO33- do not interfere with
the determination. The ions S2-, SO32-, SO42-, PO43-, [Fe(CN)6]3-, [Fe(CN)6]4-, S2O32-,
NO2-, CNS-, CN- interfere with the determination; the limits and elimination methods
are as shown in Appendix B (Normative) and Appendix C (Informative).
2 Normative references
The following standards contain provisions which, through reference in this standard,
constitute provisions of this standard. At the time of publication, the editions indicated
were valid. All standards are subject to revision and parties using this standard shall
explore the possibility of using the latest edition of the following standards.
GB/T 603-1988 Chemical reagent - Preparations of reagent solutions for use in test
methods
GB/T 6682-1992 Water for laboratory use - Specifications (neq ISO 3696:1987)
3 Method summary
In slightly acidic water or ethanol-aqueous solution, use strong ionized mercury nitrate
standard titration solution, to convert chloride ion into weakly ionized mercuric
chloride. Use diphenylcarbazone indicator and excess Hg2+ to generate purple complex
compound, so as to determine the end point.
4 Reagents and materials
The reagents and water, which are used in this standard, unless otherwise specified,
refer to analytical reagents and grade 3 water, which is specified in GB/T 6682.
The preparations and products, which are used in this standard, shall be prepared, in
accordance with the provisions of GB/T 603, unless other requirements are specified.
Safety tips: Mercury nitrate solution used in this standard is toxic; strong acid and
strong alkali are corrosive, so users shall operate with care, to avoid splashing on
the skin! If splashed on the skin, it shall be washed with water immediately, the
severe cases shall be treated immediately.
4.1 Nitric acid solution: 1 + 1.
4.2 Nitric acid solution: 1 mol/L.
Measure 63 mL of nitric acid. Use water to dilute it to 1000 mL.
4.3 Sodium hydroxide solution: 1 mol/L.
Measure 52 mL of saturated sodium hydroxide solution. Use water to dilute it to 1000
mL.
4.4 Sodium chloride standard solution: c(NaCl) = 0.1000 mol/L or c(NaCl) = 0.0500
mol/L.
Accurately weigh 5.844 g (or 2.922 g) of the benchmark sodium chloride, which was
calcined to constant weight at 500 °C ~ 600 °C, accurate to 0.0002 g. Place it in a beaker.
Add a small amount of aqueous solution to dissolve it. Transfer all the solution into a
1000 mL volumetric flask. Add water to the mark. Shake well.
4.5 Sodium chloride standard solution c(NaCl) = 0.0200 mol/L.
Dilute the sodium chloride standard solution (4.4) to the desired multiple accurately.
4.6 Mercury nitrate standard titration solution c(1/2Hg(NO3)2] of about 0.1 mol/L OR
c[1/2Hg(NO3)2] of about 0.05 mol/L.
4.6.1 Preparation: Weigh 17.13 g (or 8.57 g) of mercury nitrate [Hg(NO3)2 · H2O]. Put
it in a 250 mL beaker. Add 7 mL (or 4 mL) of nitric acid solution (4.1). Add a small
amount of aqueous solution. Filter if necessary. Transfer it into a 1000 mL volumetric
flask. Add water to the mark. Shake well.
Or, weigh 10.85 g (or 5.43 g) of mercury oxide. Put it in a 250 mL beaker. Add 20 mL
(or 10 mL) of nitric acid solution (4.1). Add a small amount of aqueous solution. Filter
if necessary. Transfer it into a 1000 mL volumetric flask. Add water to the mark. Shake
4.7.3 The amount concentration c (mol/L) of the substance in the mercury nitrate
standard titration solution is calculated, according to formula (1).
4.8 Mercury nitrate standard titration solution: c[l/2Hg(NO3)2] is about 0.01 mol/L,
c[1/2Hg(NO3)2] is about 0.005 mol/L, c[l/2Hg(NO3)2] is about 0.001 mol/L or other
concentrations.
Dilute the mercuric nitrate standard titration solution (4.6) to the required multiple
accurately. Add an appropriate amount of nitric acid solution (4.1) during dilution, to
prevent the hydrolysis of mercuric nitrate.
4.9 Bromophenol blue indicator solution: 1 g/L ethanol solution.
4.10 Diphenylcarbazone indicator solution: 5 g/L ethanol solution.
It shall be prepared again, when discoloration is insensitive.
5 Instruments and equipment
Micro-burette: Graduated value is 0.01 mL or 0.02 mL.
6 Analytical procedures
6.1 Preparation of test solutions
Weigh an appropriate amount of specimen. Use a suitable method to treat it. OR pipette
an appropriate amount of the test solution after chemical treatment [so that the
interfering ions do not exceed the specified limit, see Appendix B (normative), the
chlorine content is 0.01 mg ~ 80 mg]. Place it in a conical flask. Control the total volume
to be 100 mL ~ 200 mL (if the titration is performed in an ethanol-water solution, the
total volume shall not be greater than 40 mL; the volume ratio of ethanol to water is
3:1). Add 2 ~ 3 drops of bromophenol blue indicator solution. Adjust the pH value of
the solution to 2.5 ~ 3.5, according to one of the following steps.
If the solution is yellow, add sodium hydroxide solution (4.3) dropwise to blue. Then
add nitric acid solution (4.2) dropwise, until it is just yellow. Add another 2 ~ 6 drops
(in ethanol-water solution, it shall add another 2 ~ 3 drops);
If the solution is blue, add nitric acid solution (4.2) dropwise, until it turns yellow. Then
add another 2 ~ 6 drops (2 ~ 3 drops in ethanol-water solution).
6.2 Titration
Add 1 mL of diphenylcarbazone indicator solution, into the test solution (6.1). Use the
appropriate concentration [refer to Appendix A (normative)] of mercury nitrate standard
titration solution (4.6, 4.7, 4.8), to titrate, until the color of the test solution changes
Appendix C
(Informative)
Elimination method of interfering ions
C1 SO42-
Sulfuric acid is a dibasic acid, that interferes with the determination, due to a slight
buffering effect, which is caused by...