This standard specifies the method for determining the sodium chloride content in industrial sodium hydroxide. This standard applies to products with a sodium chloride content (mass fraction) greater than 0.005%. GB/T 4348.2-2002 Determination of sodium chloride content in industrial sodium hydroxide Mercury titration method GB/T4348.2-2002 Standard download decompression password: www.bzxz.net

GB/T 4348.2—2002
This standard is equivalent to the international standard ISO981:1973 "Determination of chlorine content of industrial sodium hydroxide - mercury method" and revised the recommended national standard GB/T4348.2—1984 "Determination of sodium fluoride content of industrial sodium hydroxide - mercury method". The main technical difference between this standard and ISO981:1973 is that the sampling volume of this standard is different from that of ISO981:1973, but the chloride content is equivalent. The main technical difference between this standard and GB/T 4348.2—1984 is that the sampling volume of this standard is different from that of GB/T4348.2—1984. The allowable difference between this standard and GB/T4348.2--1984 is different. Appendix A of this standard is a reminder appendix. This standard will replace GB/T4348.2—1984 from the date of implementation. This standard is proposed by China Petroleum and Chemical Industry Association. This standard is under the jurisdiction of the Chlor-Alkali Branch of the National Technical Committee for Chemical Standardization (TC63/SC6). The responsible drafting units of this standard are: Jinxi Chemical Research Institute, Inner Mongolia Mengxi Lian Chemical Co., Ltd. The main drafters of this standard are: Li Furong, Chen Peiyun, Ma Wenyuan, Hu Liming. This standard was first issued in 1984.
GB/T4348.2—2002
ISO Foreword
ISO (International Organization for Standardization) is a worldwide federation of national standards associations (ISO member bodies). The work of international standards is carried out by ISO technical committees. Members interested in a project for which a technical committee has been established have the right to send representatives to participate in the technical committee. International organizations, including governmental and non-governmental organizations, can also participate in this work by contacting ISO. Draft international standards adopted by technical committees are circulated to member countries for voting before being accepted as international standards by the ISO Council.
International Standard ISO981 (original draft No. 2458) was drafted by ISO/TC47, the Technical Committee on Chemistry. This standard was agreed by the following member states in January 1972: Austria
Belgium
Czechoslovakia
Hungary
Ireland
Israel
Italy
New Zealand
No member state expressed opposition.
Portugal
Spain
This international standard replaces the recommended standard ISOR981:1969 "Determination of chloride content of sodium hydroxide for industrial use
Volhard titration method".
National Standard of the People's Republic of China
Sodium hydroxide for industrial use
Determination of sodium chloride content-Mercurimetric method
Sodium hydroxide for industrial ise--Determination of sodium chloride content-Mercurimetric method This standard specifies the method for determining the sodium chloride content in sodium hydroxide for industrial use. This standard is applicable to products with a sodium nitride content (mass fraction) greater than 0.005%. 2 Reference standards
GB/T 4348.2—2002
eqv ISo 981:1973
Replaces GB/T4348.2--1984
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and the parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T603—1988 Preparation of preparations and products used in chemical reagent test methods (negISO6353-1:1982) GB/T6682--1992 Specifications and test methods for water used in analytical laboratories (eqvISO3696:1987) 3 Principle of the method
In a solution of pH 2-3, the strongly ionized standard titration solution of mercuric nitrate converts chloride ions into weakly ionized mercuric chloride, and diphenylazocarbonyl is used as an indicator to form a purple-red complex with a slightly excess of divalent mercuric ions, which is the end point. 4 Reagents and materials
The reagents and water used in this method refer to analytical pure reagents and grade 3 water specified in GB/T6682 unless otherwise specified. The preparations and products required in the test are prepared in accordance with the provisions of GB/T603 unless otherwise specified. 4.1 Nitric acid solution: 1+1.
NO; when the content is high, it has obvious interference with the titration end point. When it is found that the titration endpoint does not change significantly, the nitric acid solution needs to be re-prepared. 4.2 Nitric acid solution: 2mol/L.
4.3 Sodium hydroxide solution: 2mol/L.
4.4 Sodium chloride (reference reagent) standard solution: 0.05mol/L. Weigh 2.9221g (accurate to 0.0001g) of sodium chloride that has been dried at 500℃ for 1h to a constant weight and cooled in a desiccator, then place it in a 1000mL container, dilute with water to the scale, and shake well. 4.5 Mercuric nitrate standard titration solution: cL1/2Hg(NO,),}=0.05 mol/L. 4.5.1 Preparation of solution
Weigh 5.43g ± 0.01g mercuric oxide (HgO), place in a beaker, add 20mL nitric acid solution (4.1), add a small amount of water (filter if necessary), transfer the solution to a 1000mL volumetric flask, dilute with water to the mark, and shake well. Alternatively, weigh 8.56g ± 0.01g mercuric nitrate (Hg(NO.)2·HO) and place in a beaker, add 8ml nitric acid solution (4.2), add a small amount of water, transfer the solution to a 1000mL volumetric flask, dilute with water to the mark, and shake well. Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on May 29, 2002 102
Implemented on December 1, 2002
4.5.2 Standardization of solutions
GB/T 4348.2—2002
Pipette 25.00mL of sodium chloride standard solution (4.4) into a 250mL conical flask, add 40mL of water, then add 3 drops of bromophenol blue indicator solution, add nitric acid solution (4.2) drop by drop until the solution changes from blue to yellow, add 1mL of diphenylazocarbonylhydrazide indicator solution, and titrate with the standard titration solution of mercuric nitrate to be calibrated until the solution changes from yellow to purple-red as the end point. At the same time, use water as a blank test. The actual concentration of the standard titration solution of mercuric nitrate is calculated according to formula (1): 25
m×1000
M(V= V) × 25
Wherein: c——
-actual concentration of the standard titration solution of mercuric nitrate, mol/L; m—mass of sodium chloride standard reagent, g; V——volume of the standard titration solution of mercuric nitrate consumed in the determination, mL; V. Volume of the standard titration solution of mercuric nitrate consumed in the blank, mL; M—.-numerical value of the molar mass of sodium chloride, in grams per mole (g/mol) (M=58.443). 4.6 Standard titration solution of mercuric nitrate: c[1/2Hg(NO3),]=0.005mol/L. · (1)
Pipette 50.00mL of the calibrated mercuric nitrate standard titration solution (4.5) and place it in a 500mL volumetric flask, dilute with water [add an appropriate amount of nitric acid solution (4.1) during dilution to prevent the decomposition of mercuric nitrate] to the scale, and shake well. 4.7 Bromophenol blue indicator: 1g/L.
4.8 Diphenylazocarbonyl indicator: 5g/L. 5 Instruments and equipment
General laboratory instruments.
5.2 Microburette: 2mL, 5mL.
6 Analysis steps
6.1 Preparation of sample solution
Use a dry, clean weighing bottle of known mass to quickly weigh 36g ± 1g of solid sodium hydroxide sample or 50g ± 1g of liquid sodium hydroxide sample (accurate to 0.01g) from the sample bottle. Place the weighed sample in a 1000mL volumetric flask containing about 300mL of water, rinse the weighing bottle, add the washing solution into the volumetric flask, cool to room temperature, dilute to the scale, and shake. 6.2 Determination
Measure 50.00mL of the sample solution, place it in a 250mL conical flask, add 40mL of water, slowly add nitric acid solution (4.1) (add 5mL for solid samples and 2mL for liquid samples), cool to room temperature, add 3 drops of bromophenol blue indicator solution, the solution turns blue, then add nitric acid solution (4.1) drop by drop to change the solution from blue to yellow, add sodium hydroxide solution drop by drop to change the solution from yellow to blue, add nitric acid solution (4.2) drop by drop,Make the solution change from blue to yellow, add 1mL of diphenylazocarbonylhydrazide indicator, and titrate with standard mercuric nitrate titration solution until the solution changes from yellow to purple-red as the end point. At the same time, use water as a blank test. The mercury-containing waste liquid after titration should be retained. For treatment methods, see Appendix A (Suggested Appendix). 7 Result Expression
The sodium chloride (NaCI) content is expressed as mass fraction X, and the value is expressed in %, calculated according to formula (2): (Vo)
2(V-V.)cM
×100=
Where: c-
actual concentration of standard mercuric nitrate titration solution, mol/L; m
GB/T4348.2--2002bZxz.net
V——the volume of standard mercuric nitrate titration solution consumed in the determination, mLV. —The volume of the standard titration solution of mercuric nitrate consumed in the blank determination, mLThe mass of the sample, g;
M—The numerical value of the molar mass of sodium chloride, in grams per mol (g/mol) (M=58.443). 8 Allowable error
The absolute value of the difference between the parallel determination results shall not exceed the following values ​​(the mass fraction of sodium chloride is X): X < 0.10%: 0.005%
X≥0.10%: 0.02%
Take the arithmetic mean of the parallel determination results as the reported result. 104
GB/T4348.2-2002
Appendix A
(Suggestive Appendix)
Methods for treating waste liquid
In order to prevent the pollution of mercury-containing waste liquid, the waste liquid obtained after the mercury titration method for sodium fluoride should be treated. A1 Principle
In an alkaline medium, use excess sodium sulfide to precipitate mercury, and use hydrogen peroxide to oxidize excess sodium sulfide to prevent mercury from dissolving in the form of polysulfides.
A2 Operation steps
Collect the waste liquid in a container of about 50L. When the amount of waste liquid reaches about 40L, add 400mL of 40% industrial sodium hydroxide solution and 100g of sodium sulfide (NazS·9H,0) in turn and stir well. After 10 minutes, slowly add 400mL of 30% hydrogen peroxide solution, mix thoroughly, and after standing for 24 hours, drain the upper clear liquid into the wastewater, and transfer the precipitate to another container for recovery. A3 Description of mercuric sulfide
The solubility product constant of mercuric sulfide (also known as cinnabar) precipitate is 3×10-52, which can be considered insoluble in water and harmless to the human body. 105
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