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SN/T 0254-2020: (Calcined magnesium Determination of acid-soluble chloride Potentiometric titration)
Status: Valid SN/T 0254: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivered in | Standard Title (Description) | Status | PDF |
| SN/T 0254-2020 | English | 179 |
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(Calcined magnesium Determination of acid-soluble chloride Potentiometric titration)
| Valid |
SN/T 0254-2020
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| SN/T 0254-2011 | English | 319 |
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Determination of acid soluble chloride content in caustic calcined magnesite. Potentiometric titration method
| Obsolete |
SN/T 0254-2011
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| SN/T 0254-1993 | English | 239 |
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Method for determination of chloridein calcine magnesite for export
| Obsolete |
SN/T 0254-1993
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PDF similar to SN/T 0254-2020
Basic data | Standard ID | SN/T 0254-2020 (SN/T0254-2020) | | Description (Translated English) | (Calcined magnesium Determination of acid-soluble chloride Potentiometric titration) | | Sector / Industry | Commodity Inspection Standard (Recommended) | | Classification of Chinese Standard | H10 | | Classification of International Standard | 77.040.01 | | Word Count Estimation | 8,815 | | Date of Issue | 2020-08-27 | | Date of Implementation | 2021-03-01 | | Older Standard (superseded by this standard) | SN/T 0254-2011 | | Regulation (derived from) | General Administration of Customs Announcement No. 98 [2020] | | Issuing agency(ies) | General Administration of Customs | SN/T 0254-2020: (Calcined magnesium Determination of acid-soluble chloride Potentiometric titration)
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Caustic calcined magnesite-Determination of acid soluble chloride
content-Potentiometric titration method
The People's Republic of China Entry-Exit Inspection and Quarantine Industry Standards
Replace SN/T 0254-2011
Calcined magnesia. Determination of acid-soluble chloride. Potentiometric titration method
2020-08-27 release
2021-03-01 implementation
Issued by the General Administration of Customs of the People's Republic of China
Foreword
This standard was drafted in accordance with the rules of GB/T 1.1-2009.
This standard replaces SN/T 0254-2011 "Potentiometric Titration Method for the Determination of Acid-soluble Chloride in Calcined Magnesium".
Compared with SN/T 0254-2011, this standard has the following main changes except for editorial changes.
-Amend the title, amend "Potentiometric Titration Method for the Determination of Acid-Soluble Chloride in Calcined Magnesium" to "Determination of Acid-soluble Chloride in Calcined Magnesium"
Constant Potentiometric Titration";
- Edited revisions to the text of the 1 scope and 2 normative references;
--Prefix 7.3.3 in the original standard as 4.9.2, and delete the step of adding potassium nitrate in 4.9.2 silver nitrate solution calibration;
--In 5 instruments and utensils, add 5 mL brown burette;
- In the decomposition of 7.3.1 samples, modify some operation steps;
--In 8 Results and calculations, editorial changes were made to the text part of the calculation method;
-Edited and revised Appendix A.
This standard was proposed and managed by the General Administration of Customs of the People's Republic of China.
This standard was drafted by Dalian Customs of the People's Republic of China.
The main drafters of this standard. Hu Xiaojing, Fu Yao, Yang Yu, Zeng Ze, Li Zihao, Ren Liang, Tang Zhikun.
The previous editions of the standard replaced by this standard are as follows.
- SN/T 0254-1993, SN/T 0254-2011.
Calcined magnesia. Determination of acid-soluble chloride. Potentiometric titration method
1 Scope
This standard specifies the potentiometric titration method to determine the content of acid-soluble chloride (as Cl) in light burnt magnesia.
This standard is applicable to the determination of acid-soluble chloride (calculated as Cl) in light burned magnesia, fused magnesia, heavy burned magnesia, brucite, and magnesite.
Measuring range (mass fraction). 0.0060% to 0.02%.
2 Normative references
The following documents are indispensable for the application of this document. For dated reference documents, only the dated version applies to this article
Pieces. For undated reference documents, the latest version (including all amendments) is applicable to this document.
GB/T 1467 General rules and general provisions of the standard for chemical analysis methods of metallurgical products
GB/T 6379.2 Accuracy of measurement methods and results (accuracy and precision) Part 2.Determine the repeatability of standard measurement methods
Basic methods with reproducibility
GB/T 6682 Analytical laboratory water specifications and test methods
GB/T 12805 Laboratory glass burette
GB/T 12806 Laboratory glassware single mark volumetric flask
GB/T 12808 Single-marked pipette for laboratory glassware
3 Method summary
The sample is decomposed by nitric acid, and under the condition of pH 2～4, the chloride ion selective electrode or silver electrode is used as the measuring electrode, and the double salt bridge calomel electrode
It is a reference electrode, titrated with silver nitrate standard solution, according to the potential jump, the second-level derivative method is used to calculate the titration end point.
4 Reagents and materials
Unless otherwise specified in the analysis, only use reagents confirmed to be analytically pure and secondary water that meets the requirements of GB/T 6682 or whose purity is comparable.
When the water.
4.1 Sodium chloride reference reagent.
4.2 Silver nitrate reagent, excellent grade pure.
4.3 Thymol blue indicator.
4.4 Sodium hydroxide reagent, excellent grade pure.
4.5 Nitric acid (ρ 1.42 g/mL).
4.6 Nitric acid solution (1 3).
4.7 Sodium hydroxide solution (200 g/L). Weigh 50 g of sodium hydroxide (4.4), dissolve it in 250 mL of water, and transfer it to a plastic bottle for later use.
4.8 Sodium chloride reference solution (0.010 00 mol/L). Weigh the sodium chloride reference reagent (4.1) that has been previously burned at 500 ℃ to 600 ℃ to a constant weight
Put 0.5845 g in a 150 mL beaker, add water to dissolve, transfer to a 1000 mL volumetric flask, dilute to the mark with water, and shake well.
4.9 Silver nitrate standard solution (0.01 mol/L)
a) Preparation. Weigh 1.699 g of premium grade pure silver nitrate (4.2) that has been dried at 105 ℃ for 2 hours in a small 150 mL beaker, and add
After the water is dissolved, transfer it to a 1000 mL brown volumetric flask, dilute to the mark with water, and shake well. This solution should be stored away from light.
b) Calibration. Pipette 5.00 mL sodium chloride reference solution (4.8) into a 100 mL small beaker, add 50 mL water, and put it in the electromagnetic stirrer
Stir, place the beaker on a magnetic stirrer, stir slightly, add 2 to 3 drops of thymol blue indicator (4.10), and add nitric acid solution dropwise
(4.6) When the solution is red, adjust it to yellow with sodium hydroxide solution (4.7). At this time, the pH value is about 3-4.Insert measuring electrode and reference
Electrode, record the initial potential value, and then titrate with silver nitrate standard solution (4.9). Add 4mL silver nitrate standard solution (4.9) in advance,
Then add 0.20 mL silver nitrate standard solution (4.9) one by one, and record the cumulative volume after each addition of silver nitrate standard solution (4.9)
Corresponding potential value, after the potential jump occurs, continue to drip 0.20 mL silver nitrate standard solution (4.9) for 2 to 3 times, and continue to record the accumulation
Volume and corresponding potential value. The volume of the silver nitrate standard solution (4.9) added each time during the titration should be the same. Calculate according to the appendix
Point volume and calculate the concentration of silver nitrate standard solution according to formula (1).
4.10 Thymol blue indicator (1 g/L). Weigh 0.1 g of thymol blue (4.3) and dissolve it in 100 mL of ethanol (200 ml/L) solution.
4.11 Ethanol solution (200 ml/L).
5 Instruments and utensils
Unless otherwise specified, the volumetric flasks, burettes and pipettes used must comply with GB/T 12805, GB/T 12806, GB/T 12808
Regulations.
5.1 Brown burette, with a minimum graduation of 0.02 mL or 0.05 mL, and a capacity of 5 mL or 10 mL.
5.2 Single-marked volumetric flasks, with capacities of 500 mL and 1000 mL.
5.3 Single-marked pipette with a capacity of 5mL.
5.4 Analytical balance, with a sensitivity of 0.1 mg.
5.5 Ion meter (or automatic potentiometric titrator), with a sensitivity of 0.1 mV.
5.6 Measuring electrode, chloride ion selective electrode (or composite silver ring electrode).
5.7 Reference electrode, double salt bridge calomel electrode.
5.8 Magnetic stirrer and stir bar.
5.9 Oven. The temperature can be controlled at 105 ℃ ± 5 ℃.
5.10 Standard sieve. 75 μm.
6 Sample preparation
Prepare the sample in accordance with GB/T 1467, and the sample should pass through a 75 μm standard sieve. Dry for 2 h at 105 ℃ ±5 ℃, and place in a desiccator
Save in.
7 Analysis steps
7.1 The amount of sample
Weigh 2 g～5 g dry sample, accurate to 0.0002 g. Do parallel determinations of two samples at the same time.
Note. If the chloride ion content in the sample is less than 0.01%, weigh 5 g of the sample; if the chloride ion content in the sample is higher than 0.01%, weigh 2 g of the sample.
7.2 Blank test
Do a blank test with the sample.
7.3 Determination
7.3.1 Decomposition of the sample
Place the sample (7.1) in a 150 mL beaker, add 5 mL to 10 mL of water, put it into the electromagnetic stir bar, and place the beaker under magnetic stirring
On the vessel, cover with a watch glass, slowly add 10 mL to 20 mL of nitric acid (4.5) dropwise under constant stirring, taking care to prevent the solution from violent reaction bumping.
Stir for 10 minutes until the sample no longer dissolves, remove it, make up to 50 mL of water, and cool to room temperature.
Note. If the sample is not completely dissolved, it will not affect the measurement.
7.3.2 Determination
Place the beaker on the electromagnetic stirrer again, add 2 to 3 drops of thymol blue (4.10) indicator, and add sodium hydroxide solution dropwise
(4.7), make the solution just turn pale yellow, and the pH value is about 2～4.
Note. If the solution is yellow-brown after the sample is decomposed, and the indicator color is not obvious, it can be adjusted to pH 2～pH 4 with pH test paper, or quickly filtered
After filtration, adjust the pH value with thymol blue indicator and measure it.
Insert the measuring electrode (5.6) and the reference electrode (5.7), and measure the initial potential value with an ion meter. Then use silver nitrate standard solution (4.9)
Titrate, add 0.20 mL each time, record the cumulative volume of the silver nitrate standard solution consumed and the corresponding potential value, wait for a potential jump
Then continue to drip 0.20 mL silver nitrate standard solution (4.9) 2 times to 3 times, and record the cumulative volume and the corresponding potential value. Use secondary micro
The quotient method calculates the volume Vep of the silver nitrate standard solution consumed at the end of the titration. Refer to Appendix A for the calculation method.
8 Result calculation
Calculate the mass fraction of acid-soluble chloride (calculated as Cl) according to formula (2) ω,%
Vep - the volume of the silver nitrate standard titration solution consumed at the end of the titration, in milliliters (mL);
V0 - The volume of the silver nitrate standard titration solution consumed at the end of the blank, in milliliters (mL);
C1-the concentration of silver nitrate standard titration solution, the unit is moles per liter (mol/L);
m-the mass of the sample, the unit is grams (g);
0.03545 - The millimolar mass of chlorine, in grams per millimole (g/mmol).
The analysis result retains 2 significant figures.
9 Precision
9 laboratories conduct method precision tests on 5 levels of samples, and calculate the precision according to GB/T 6379.2.The results are shown in Table 1.
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