GB/T 3051-2000 General method for determination of chloride content in inorganic chemical products - Mercury titration method
Some standard content:
GB/T3051—2000
This standard adopts ISO5790:1979 "General method for determination of fluoride content in industrial inorganic chemical products - mercury titration" in a non-equivalent manner, and revises GB/T3051-1982 "General method for determination of fluoride content in inorganic chemical products - mercury titration". The main technical differences between this standard and ISO5790:1979 are as follows: The measurement range is expanded. ISO5790 is applicable to chlorine content exceeding 1mg, while this standard is applicable to chloride content of 0.01mg~80mg.
The titration medium of ethanol-water solution is added. ISO5790 only stipulates one titration medium, aqueous solution, while this standard stipulates two titration media, aqueous solution and ethanol-water solution. It is stipulated that when using a standard titration solution below 0.02mol/L, titration should be carried out in an ethanol-water solution medium.
The volume of the tested liquid is reduced. ISO5790 stipulates that the volume of the tested liquid should be controlled at 200mL~350mL, and this standard stipulates that the volume of the tested liquid should be controlled at 100mL~200mL (should not exceed 40mL in ethanol-water solution). Through a large number of experiments, six new ions that interfere with the determination, including CN-, [Fe(CN), J3-, [Fe(CN). 7, CNS-, NO;, S, O\, and their non-interference limits were added.
Through experimental verification, the non-interference limits of four ions, including SO, SO-, Fe2+, and PO-, were adjusted. The exclusion methods of seven interfering ions, including CN-, [Fe(CN). 3- and [Fe(CN). J-, NH, F-, CNS-, NO, S, O-, were added.
The main technical differences between this standard and the original national standard are: five substances or ions that interfere with the determination, such as NaNO:, KNO:, SiO2, CH,COONa, and Fe+, are added, and their non-interference limits are specified in the same way as ISO5790. The common interfering substances SiOz, A13+, Zn2+, Mg2+, Fe3+, Mn2+, Cu2+Ni2+, Cr3+Co2+ and their non-interference limits and exclusion methods are specified in the same way as ISO 5790. The exclusion method of the interfering ion Cr3+ is added, and this method is equivalent to ISO5790. This standard replaces GB/T3051-1982 (1989) from the date of implementation. Appendix A and Appendix B of this standard are standard appendices; Appendix C and Appendix D are suggestive appendices. This standard was proposed by the former Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Inorganic Chemical Branch of the National Technical Committee for Chemical Standardization. The drafting units of this standard are: Tianjin Chemical Research and Design Institute of the Ministry of Chemical Industry, Qingdao Entry-Exit Inspection and Quarantine Bureau. The main drafters of this standard are: Yao Jinjuan, Shi Jie, Zhang Ping, Xue Junhua, Liu Liang, Cui He. This standard was first issued in April 1982 and confirmed in 1989. The Inorganic Chemical Branch of the National Technical Committee for Chemical Standardization is responsible for the interpretation of this standard. 24
National Standard of the People's Republic of China
General method for determination of chloride content in inorganic chemical products--Mercurimetric method
GB/T 3051-2000
neqIso5790:1979
Replaces GB/T3051-1982(1989)
Inorganic chemical products for industrial use--General methodfor determination of chloride content--Mercurimetric method1Scope
This standard specifies the general method for determination of chloride content in inorganic chemical products--Mercurimetric method. This standard is applicable to samples with a nitride (as Cl) content of 0.01mg~~80mg. When the concentration of the mercuric nitrate standard solution used is less than 0.02mol/L, the titration should be carried out in ethanol-water solution. K+, Na+, Ca2+, Mg2+, Ba2+, Zn2+, Pb2+, NO;, CO-, BO- ions do not interfere with the determination; S2-, SO\, SO-, PO\-, [Fe(CN)3-, [Fe(CN)]-, S,O-, NO2, CNS-, CN- and other ions all interfere with the determination. For their limits and exclusion methods, please refer to Appendix B (Standard Appendix) and Appendix C (Suggestive Appendix). 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards will be revised, and 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 GB/T6682—1992 Specifications and test methods for water used in analytical laboratories (negISO3696:1987) 3 Method summary
In slightly acidic water or ethanol-water solution, use a strongly ionized mercuric nitrate standard titration solution to convert fluoride ions into weakly ionized mercuric fluoride, and use diphenylazocarbonyl hydrazide indicator to generate a purple-red complex with excess Hg2+ to determine the end point. 4 Reagents and materials
The reagents and water used in this standard, unless otherwise specified, refer to analytically pure reagents and grade 3 water specified in GB/T6682. The preparations and products used in this standard, unless otherwise specified, are prepared in accordance with the provisions of GB/T603. Safety tips: The mercuric nitrate solution used in this standard is toxic, and strong acids and alkalis are corrosive. Users should operate with caution to avoid splashing on the skin! If splashed on the skin, rinse with water immediately. In severe cases, seek medical treatment immediately. 4.1 Nitric acid solution: 1+1.
4.2 Nitric acid solution: 1mol/L.
Measure 63mL nitric acid and dilute with water to 1000mL4.3 Sodium hydroxide solution: 1mol/L.
Measure 52mL saturated sodium hydroxide solution and dilute with water to 1000mL. 4.4 Sodium chloride standard solution: c(NaCI)==0.1000mol/L or c(NaCI)=0.0500mol/L. Weigh 5.844g (or 2.922g) of standard sodium chloride burned to constant weight at 500℃～600℃ accurately to 0.0002g, place it in a beaker, add a small amount of water to dissolve, transfer all the solution into a 1000mL volumetric flask, add water to the scale, and shake well. 4.5 Sodium chloride standard solution: c(NaCl)=0.0200mol/L. Dilute the sodium fluoride standard solution (4.4) accurately to the required multiple. 4.6 Mercuric nitrate standard titration solution: c[1/2Hg(NO3)2] is about 0.1mol/L or c[1/2Hg(NO:),] is about 0.05mol/L. 4.6.1 Preparation: Weigh 17.13g (or 8.57g) mercuric nitrate EHg(NO)2·H,O7, place in a 250mL beaker, add 7mL (or 4mL) nitric acid solution (4.1), add a small amount of water to dissolve, filter if necessary, transfer to a 1000mL volumetric flask, add water to the mark, and shake well. Alternatively, weigh 10.85g (or 5.43g) mercuric oxide, place in a 250mL beaker, add 20mL (or 10mL) nitric acid solution (4.1), add a small amount of water to dissolve, filter if necessary, transfer to a 1000mL volumetric flask, add water to the mark, and shake well. 4.6.2 Calibration: Use a pipette to transfer 25 mL of sodium chloride standard solution (4.4) and place it in a conical flask. Add 100 mL of water and 23 drops of bromophenol blue indicator solution. Add nitric acid solution (4.2) until the solution changes from blue to yellow. Then add 2 to 6 drops in excess. Add 1 mL of diphenylazocarbonylhydrazide indicator solution. Titrate with a corresponding concentration of mercuric nitrate standard titration solution until the solution changes from yellow to purple-red. Keep the mercury-containing waste liquid after titration and treat it according to the provisions of Appendix D (Suggested Appendix). Perform a blank test at the same time.
4.6.3 The molar concentration c (mol/L) of the mercuric nitrate standard titration solution is calculated according to formula (1): cVi
Where: C1—actual concentration of sodium chloride standard solution, mol/L, V,—volume of sodium chloride standard solution transferred, mL; V——volume of mercuric nitrate standard titration solution consumed in titration, mL, V. The volume of the standard titration solution of mercuric nitrate consumed in titrating the blank test solution, mL. 4.7 Standard titration solution of mercuric nitrate: c[1/2Hg(NO3)2] is about 0.02 mol/L. (1)
4.7.1 Preparation: Dilute the standard titration solution of mercuric nitrate (4.6) accurately by the required multiple. When diluting, add an appropriate amount of nitric acid solution (4.1) to prevent the hydrolysis of mercuric nitrate.
4.7.2 Calibration: Use a pipette to transfer 5 mL of sodium fluoride standard solution (4.5), place it in a conical flask, add 5 mL of water, 30 mL of ethanol, 2 drops of bromophenol blue indicator solution, and add nitric acid solution (4.2) until the test solution changes from blue to yellow. Then add 2-3 drops of excess, add 1 mL of diphenylazocarbonylhydrazide indicator solution, and titrate with a corresponding concentration of mercuric nitrate standard titration solution until the color of the test solution changes from yellow to purple-red. At the same time, perform a blank test.
4.7.3 The molar concentration c (mol/L) of the mercuric nitrate standard titration solution is calculated according to formula (1). 4.8 Mercuric nitrate standard titration solution: c[1/2Hg (NO),] is about 0.01 mol/L, c[1/2Hg (NO,)] is about 0.005 mol/L, cL1/2Hg (NO,),) is about 0.001 mol/L or other concentrations. Dilute the standard titration solution of mercuric nitrate (4.6) accurately to the required multiple. When diluting, add an appropriate amount of nitric acid solution (4.1) to prevent the hydrolysis of mercuric nitrate.
4.9 Bromophenol blue indicator solution: 1g/L ethanol solution. 4.10 Diphenylazocarbonyl hydrazide indicator solution: 5g/L ethanol solution. If the color change is not sensitive, re-prepare.
5 Instruments and equipment
Microburette: graduation value is 0.01mL or 0.02mL 6 Analysis steps
6.1 Preparation of test solution
Weigh an appropriate amount of sample and treat it with an appropriate method, or transfer an appropriate amount of test solution after chemical treatment so that the interfering ions do not exceed the specified limit, see Appendix B (Appendix of the standard), chlorine content is 0.01mg~80mg], place it in a conical flask, control the total volume to 100mL~200mL26
GB/T 3051—2000
(If the titration is carried out in ethanol-water solution, the total volume should not be greater than 40mL, and the volume ratio of ethanol to water is 3:1), add 2~3 drops of bromophenol blue indicator solution, and 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) until it turns blue, then add nitric acid solution (4.2) until it turns yellow, and then add 2 to 6 drops (2 to 3 drops in ethanol-water solution); if the solution is blue, add nitric acid solution (4.2) until it turns yellow, and then add 2 to 6 drops (2 to 3 drops in ethanol-water solution);
6.2 Titration
Add 1 mL of diphenylazocarbonyl hydrazide indicator solution to the test solution (6.1), and titrate with a standard titration solution of mercuric nitrate (4.6, 4.7, 4.8) of appropriate concentration (refer to Appendix A (Standard Appendix)) until the color of the test solution changes from yellow to purple-red. Perform a blank test at the same time.
7 Description of analytical results
The chloride content X expressed as a mass percentage (calculated as Cl) is calculated according to formula (2): X(%) (V-Vo)c× 0.03545 × 100 = c(V-Vo) × 3.545. mbZxz.net
Wherein: c—actual concentration of standard mercuric nitrate titration solution, mol/L; V—volume of standard mercuric nitrate titration solution consumed by titrating the test solution, mL; V—volume of standard mercuric nitrate titration solution consumed by titrating the blank test solution, mL; m—
· (2)
The mass of the sample contained in the titration solution, g: the mass of chlorine in grams equivalent to 1.00mL of standard mercuric nitrate titration solution [c[1/2Hg(NO3:)]-1.000mol/L].
GB/T 3051—2000
Appendix A
(Appendix of standard)
Fluoride ion content in test solution and concentration of corresponding standard titration solutionThis appendix provides the expected chloride content (measured in Cl) in the test sample and the recommended concentration of the standard titration solution. See Table A1:Table A1
Cl content in sample, mg
Concentration of standard titration solution, mol/L
0. 001~～0. 02
Appendix B
(Appendix of standard)
0.02~0.03
Ions that do not interfere with determination and ions that interfere with determination and their limits25~80
0.03～0.1
This appendix gives the limits of some non-interfering ions (Table B1) and interfering ions (Table B2) when titrating in aqueous solution and the reasons for their provisions.
Table B1 Ions that do not interfere with determination
Ion name
CO (as CO,)
Ion name
EFe(CN). J*
Limit of non-interference
, mg/L
Table B2 Ions interfering with determination
Reasons for specified limits
Has slight buffering effect
Reacts with Hg2+
Forms HgS precipitate
Appears turbid and slightly yellow when neutralized
Oxydiphenylazocarbohydrazide
Forms precipitate or complex with Hg?+
Forms precipitate with Hg?+
Limit of non-interference, g/L
Possible elimination methods
See C1 in Appendix C
See C2 in Appendix C
See C3 in Appendix C
See C4 in Appendix C
See Appendix C C5
See Appendix C C6
See Appendix C C7
Ion name
[Fe(CN). J3-
CH,COONa
Ions or compounds
Limit of non-interference
, mg/L
Limit of non-interference
GB/T 3051—2000
Table B2 (end)
Reasons for setting limits
Precipitation with Hg*+
Reaction with Hg*
Precipitation with Hg2+
Generation of HgF2
Forming a complex
Reaction with Hg2+
Reaction with Hg*+
Buffering effect
Forming Al(OH): precipitation adsorption indicator
Displaying the color of the ion itself
Displaying the color of the ion itself
Displaying the color of the ion itself
Producing a color change reaction with diphenylazocarbohydrazide to form a precipitate
Complexation with CI
Generation of AgCI Precipitation
Prevent HgClE generation
Color change is lower than sensitivity
Generate difficult-to-bath hydroxides
Table B3 Co-existing interfering substances
Reasons for specifying limits
Produce precipitates with adsorption
Possible elimination methods
See Appendix C C7
See Appendix C C8
See Appendix C C9
See Appendix C C10
See Appendix C C11
See Appendix C C12
Control the required pH value or use potentiometric titration
Use potentiometric titration
Use potentiometric titration
Use potentiometric titration
Control the required pH Value
Exclusion method
Add 5gNa,P,O,·10H,OC per liter. Under this condition, the solution is slightly turbid and only causes slight interference (color change, accuracy reduced by half)) 29
GB/T3051-2000
Appendix C
(Suggested Appendix)
Exclusion method of interfering ions
Sulfuric acid is a dibasic acid. It interferes with the determination due to a slight buffering effect caused by step ionization. The exclusion method is: add an excess of 1moi/L nitric acid solution (generally 1mL~~2mL), depending on the different SO- content, strictly control the required pH value, and it is recommended to use a pH meter to control it during the initial adjustment. C2 SOf~
In an acidic solution, SO- reacts with Hg2+, consumes the standard titration solution of mercuric nitrate, and interferes with the determination. In an alkaline medium, SOF- is oxidized to SO with hydrogen peroxide. The exclusion method is: when the content is below 10g/L, adjust the solution to be tested to near neutrality (use bromophenol blue as an indicator to change from yellow to blue), then add 2mL of 1mol/L sodium hydroxide solution, slowly drop an appropriate amount of 30% hydrogen peroxide solution, heat slightly, and finally heat and boil until no small bubbles are generated. After cooling, adjust the pH value with nitric acid and wait for determination. C3S2-
S2- and Hg2+ generate HgS precipitate, which affects the determination. Use hydrogen peroxide to oxidize S2- to SO- in an alkaline medium. The exclusion method is the same as C2. C4 Fe2+
When the content is above 0.3g/L, precipitation occurs during neutralization. When the content is below 1 g/L,After adding 4 drops of 1 mol/L nitric acid solution, the precipitate immediately dissolves, and the slight yellow color does not affect the observation of the endpoint.
C5Cro and Cr03
CrO2- first turns into Cr2O%- (orange-red) in acidic medium. Cr2O- has strong oxidizing properties, which oxidizes diphenylazocarbonyl hydrazide and affects the determination.
When the CrO2- content is less than 50mg/L, add diphenylazocarbonyl hydrazide and titrate immediately, and the end point color changes from orange-red to purple-red. When the content is greater than 50mg/L, add an appropriate amount of barium nitrate to generate BaCrO, precipitate, filter and remove CrO?-, but the procedures are complicated. It is recommended to use potentiometric titration for determination.
C6 CN~
CN- generates Hg(CN) precipitate or Hg(CN) complex with Hg2+. The exclusion method is: add formaldehyde twice the CN- content to the test solution. Leave it for 20 minutes, then adjust the pH value with nitric acid and wait for determination. C7［Fe(CN),]4- and EFe(CN), J3-
[Fe(CN). ]4- and [Fe(CN). ]3- react with Hg2+ to form a precipitate, affecting the determination. The elimination method is: add 2~3 times the amount of zinc nitrate as the sample to the test solution, heat to boiling, cool, transfer all into a volumetric flask, add water to the scale, shake well, and let it stand for stratification. Dry filter with slow filter paper, discard the initial filtrate, and use the remaining filtrate for determination. C8NHt
NH+ reacts with Hg2+, consumes the standard titration solution of mercuric nitrate, and affects the determination. The elimination method is: adjust the test solution to alkaline, heat, boil, and drive away NHs. 30
C9 CNS-
GB/T3051--2000
CNS- and Hg2+ generate Hg(CNS), which precipitates and interferes with the determination. The elimination method is: slowly add an appropriate amount of 30% hydrogen peroxide solution to the test liquid, heat and boil until no small bubbles are generated. The operation should be carried out in a fume hood.
When the NO2 content is greater than 10mg/L, there is obvious interference with the determination. The elimination method is: when the content is below 1g/L, add 100g/L aminosulfonic acid solution to the sample containing NO; until no bubbles are generated.
When the F- content is greater than 0.1g/L., the color of the titration endpoint changes slowly and it is difficult to determine the endpoint. Adding acid can eliminate its interference. The amount of addition is 0.4z boric acid when the F- content is not greater than 1.2g/L. C12 S203
S,O- and Hg2- form a complex, interfering with the determination. The elimination method is: add 2 drops of 2mol/L sodium hydroxide solution to the test solution, slowly add an appropriate amount of 30% hydrogen peroxide solution, heat slightly, and finally heat and boil until no small bubbles are generated. C13 Cr3+
When the content is below 200 mg/L, the bromophenol blue indicator cannot indicate the end point of neutralization. The elimination method is to add 1mol/L sodium hydroxide solution until the test solution turns yellow-green, then add 1mol/L nitric acid solution until the test solution turns blue-gray, and add 3 drops in excess.
Appendix D
(Suggested Appendix)
Methods for treating waste liquid
In order to prevent the pollution of mercury-containing waste liquid, it is recommended to treat the waste liquid obtained after the mercury titration method for chloride determination. D1 Method Summary
In 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 polysulfide.
D2 Analysis Steps
Collect the waste liquid in a container of about 50L. When the waste liquid reaches about 40L, add 400ml of 400g/L sodium hydroxide solution and 100g of sodium sulfide (NazS·9H.0) in sequence and spread evenly. After 10min, slowly add 400mL of 30% hydrogen peroxide solution and mix thoroughly. After standing for 24h, drain the upper clear liquid into the wastewater, transfer the precipitate to another container, and have a dedicated person collect the mercury. The reagents used in the above operations are all industrial grade. 31
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