Some standard content:
JB/T 7994--1999
This standard is a revision of JB/T7994--95 (formerly GB9256--88) "Chemical Analysis Method for Cubic Boron Nitride".
This standard is basically consistent with the technical content of JB/T7994--95, and has only been re-edited according to relevant regulations. This standard replaces JB/T7994--95 from the date of implementation. This standard is proposed and managed by the National Technical Committee for Standardization of Abrasives and Grinding Tools. The drafting unit of this standard: Zhengzhou Abrasives and Grinding Research Institute. The main drafters of this standard: Cheng Ruida, Kang Jichang. This standard was first issued on May 23, 1988. 44
1 Scope
Standard of the Machinery Industry of the People's Republic of China
Chemical Analysis Methods
Cubic Boron Nitride
Chemical Analysis Methods of Cubic Boron NitrideJB/T 7994-1999
Replaces JB/T7994-95
This standard specifies the chemical analysis methods of boron nitride, silicon trioxide, iron trioxide, aluminum trioxide, calcium oxide, and magnesium oxide. This standard applies to the chemical analysis of cubic boron nitride. 2 General Provisions
2.1 During arbitration analysis, the number of parallel copies of the same sample shall not be less than three. If the difference in the analysis results is within the allowable range, the arithmetic mean shall be taken as the final analysis result.
2.2 Unless otherwise specified, the reagents used in the analysis shall not be less than analytical grade. The reference reagent shall be used as the reference reagent. Unless otherwise specified, the water used for analysis shall be distilled water or deionized water. 2.3 Liquid reagents whose concentrations are not specified in the method refer to concentrated solutions. The percentage concentration of a solution is the mass/volume percentage concentration, which refers to the number of grams of solute contained in 100 mL of solution, while (1 + 1), (1 + 2), (m + n), etc., refer to the ratio of the solute volume to the water volume. 2.4 The sensitivity of the analytical balance should reach 0.1 mg, and the magnetic code should be checked regularly. 2.5 Burettes, volumetric flasks, pipettes and other measuring instruments must be calibrated. 2.6 All operations in the method are carried out in glassware unless otherwise specified. 2.7 In each determination, a blank test should be performed at the same time to calibrate the analytical results. 2.8 The analytical sample should be dried at 105~110C for 1 hour and placed in a desiccator to cool to room temperature. 3 Neutralization method for determination of boron
3.1 Method summary
After the sample is melted with alkali, it is leached with water and acidified with acid to convert boron into boric acid. Then calcium carbonate is added to separate boron from other impurity elements. Finally, the boric acid is titrated with sodium hydroxide standard solution. During titration, a certain amount of mannitol is added to make it complex with boric acid to form a stronger acid, which is conducive to the neutralization reaction.
3.2 Reagents
3.2.1 Sodium hydroxide (solid).
3.2.2 Hydrochloric acid (density 1.19).
3.2.3 Methyl red indicator: 0.1% ethanol solution. Weigh 0.1g of methyl red indicator, dissolve it in 60mL. ethanol, and dilute it to 100ml with water..
3.2.4 Phenolic acid indicator: 1% ethanol solution. Weigh 1g of phenolic acid indicator, dissolve it in 80mL. ethanol, and dilute it to 100mL with water. 3.2.5 Calcium carbonate (solid).
3.2.6 Mannitol (solid).
3.2.7 Sodium hydroxide standard solution (0.1N): a) Weigh 4g of sodium hydroxide (solid) and dissolve it in freshly boiled and cooled water, add a little barium chloride, dilute to 1000mL, and transfer it into a plastic bottle for later use.
JB/T7994——1999
b) Calibration: Accurately weigh 0.3g of potassium hydrogen phthalate (solid) after drying at 105～110℃ for 1h. Place it in a 250mL conical flask, add about 100mL of freshly boiled, cooled and neutralized with 0.1N sodium hydroxide until the phenolic acid indicator turns slightly red, shake it to dissolve, add 2~3 drops of phenolic acid indicator (1%), and titrate with sodium hydroxide standard solution (0.1N) until it turns slightly red as the end point. The equivalent concentration of sodium hydroxide standard solution is calculated according to formula (1): m
N = 0. 204 2V
Where: m-mass of potassium hydrogen phthalate gbzxz.net
V volume of sodium hydroxide standard solution consumed during titration, mL; 0.2042-milligram equivalent of potassium hydrogen phthalate. 3.3 Analysis method
Weigh 0.1000g of sample into a silver crucible (or nickel crucible), add 3g of sodium hydroxide (solid), cover it with a lid slightly ajar, put it into a high-temperature furnace, heat it from room temperature to 700°C, and melt it for 10-15min. Take it out and rotate the glass to make the molten material adhere to the wall of the crucible. Use hot water to immerse the molten material in a 250mL beaker, add 7mL of hydrochloric acid (density 1.19), and heat to boil for 5-10min. Remove and cool slightly, add 2-3 drops of methyl red indicator (0.1%), add calcium carbonate in batches until a small amount of insoluble calcium carbonate is found at the bottom of the beaker, heat and boil for 5 minutes, cool slightly, filter with rapid quantitative filter paper, wash the beaker with hot water, wash the precipitate and filter paper 78 times, discard the precipitate and filter paper, collect the filtrate and washings in a 300ml conical flask, add 1 drop of hydrochloric acid (1+1), heat and boil for 5-10 minutes to remove carbon dioxide, cool with running water, immediately neutralize the excess acid with 0.1N sodium hydroxide standard solution until the solution just turns yellow (ignore the reading), add 4 drops of phenolic acid indicator (1%) and 2-3g of mannitol (solid), drip with sodium hydroxide standard solution (0.1N) until it turns slightly red, then add a small amount of mannitol. If the red color disappears, drip with 0.1N sodium hydroxide standard solution until it turns slightly red, and repeat this process until the slightly red color in the solution no longer disappears after adding mannitol, which is the end point. Calculate the redistribution content of boron nitride according to formula (2): BN 0. 024 82NV
Wherein: N—…-equivalent concentration of sodium hydroxide standard solution; × 100%
V—--volume of sodium hydroxide standard solution consumed during titration, mL; m—sample mass + g;
0.02482—·milligram equivalent of boron nitride. 3.4 Allowable error
The difference in analysis results between laboratories should not exceed 0.60%, and the allowable difference within a laboratory should be less than 0.60%. 4 Determination of silicon dioxide by molybdenum blue photometric method
4.1 Summary of the method
After the sample is decomposed with alkali, it is acidified with hydrochloric acid. In a 0.150.25N hydrochloric acid medium, ammonium molybdate is added to make the silicate ions form silicomolybdic heteropoly acid, which is reduced to molybdenum blue with 1-amino-2-phenol-4-sulfonic acid reducing agent. Its absorbance is measured at a wavelength of 700nm on a spectrophotometer. 4.2 Reagents
4.2.1 Sodium hydroxide (solid).
4.2.2 Hydrochloric acid (density 1.19).
4.2.3 Ammonium sawdioxide solution (5%).
4.2.4 Tartaric acid solution (5%).
4.2.51,2,4-acid (1-amino-2-naphthol-4-sulfonic acid) reducing agent: dissolve 0.15g of 1,2,4-acid, 0.17g of anhydrous sodium sulfite and 9g of sodium sulfite in water, dilute to 100mL with water, store in a plastic bottle for later use, and the usage time is 14d. 4.2.6 Silicon dioxide standard solution a) Accurately weigh 0.0500 g of silicon dioxide (reference reagent) calcined at 980-1000°C for 1 h in a platinum crucible, add 2 g of anhydrous sodium carbonate (reference reagent), mix carefully and cover with 0.5 g, melt at 860-900°C for 20 min, take out, rotate the crucible to allow the molten material to adhere to the inner wall of the crucible, cool, wash the outer wall, and soak it in hot water in a polyethylene beaker. After cooling, transfer it to a 500 ml volumetric flask, dilute with water to the mark, shake, and immediately transfer it to a clean and dried plastic bottle for storage. This solution contains 0.1 mg silicon oxide per ml. b) Weigh 20 mL of silica standard solution (0.1 mg/mL) into a 200 mL volumetric flask pre-filled with 10 mL of hydrochloric acid (2N), dilute to the mark with water, and shake well. This solution is the standard solution containing 0.01 mg of silica per mL. 4.2.7 Blank solution: Weigh 10 g of sodium hydroxide (solid) into a silver crucible, send it into a high-temperature furnace, heat from room temperature to 700C to melt for 5 minutes, take it out, cool it, soak it in hot water in a 250 mL beaker, immediately add 33 mL of hydrochloric acid (density 1.19), heat and boil for 5 minutes, transfer it to a 200 mL volumetric flask, cool it, dilute to the mark with water, and shake well. 4.3 Drawing of working curve
Take 9 portions of 10 ml of blank solution and place them in a group of 50 ml volumetric flasks. Then add 0.00, 0.50, 1.00, 2.00, 3.00, 4.00, and 5.00 ml of silicon monoxide standard solution (0.1 mg/mL) in sequence.6.00, 8.00, 10.00ml, dilute to 30ml with water, adjust the test solution temperature to 20~25C, add 5ml of ammonium molybdate (5%), let it stand for 10min, add 10ml of tartaric acid (5%), 3mL of l,2,4-acid reducing agent, dilute to the scale with water, shake the hook, let it stand for 30min, use 1cm thick colorimetric III on a spectrophotometer at a wavelength of 700nm, use water as a reference to measure its absorbance, subtract the absorbance of the blank, and draw a working curve. 4.4 Preparation of test solution
Accurately weigh 0.2000g of the sample and place it in silver. Add 4g of sodium hydroxide (solid). Cover with a lid slightly ajar and place in a high-temperature furnace. Heat the temperature from room temperature to 700℃ and melt for 10min. Take it out and rotate the crucible to allow the molten material to adhere to the inner wall of the crucible. After cooling, immerse it in hot water in a 250mL beaker. Immediately add 13mL of hydrochloric acid (density 1.19), heat and boil for 5-10min. Take it out and transfer it to a 200ml volumetric flask after cooling. Dilute it to the mark with water and shake it for later use.
4.5 Analysis method
Pipette 25 ml of the test solution prepared in 4.4, place it in a 50 ml volumetric flask, add 5 ml of water, adjust the temperature of the test solution to 20~~25°C, add 5 ml of ammonium molybdate solution (5%), let it stand for 10 min, add 10 ml of tartaric acid solution (5%)1,2.4-acid reducing agent 3 ml, dilute with water to the scale, spread, let it stand for 30 min, use a 1 cm thick colorimetric dish on a spectrophotometer at a wavelength of 700 nm, use water as a reference to measure its absorbance, after subtracting the blank test absorbance, find out the silicon dioxide content on the working curve. Calculate according to formula (3): Silicon oxide percentage: (SiO,)-
Wherein: m-
Silicon dioxide amount found from the working curve + sample mass g;
VTotal volume of test solution, ml;
V..…Volume of test solution, mL
4.6 Allowable error
X 100%
The difference between the analysis results of laboratories should not be greater than the allowable error listed in Table 1, and the allowable error within the laboratory should be less than the value shown in Table 1. Table 1
Silicon dioxide
0.41~0.80
5 Determination of ferric oxide by o-phenanthroline colorimetric method 5.1 Method summary
Allowable error
High-valent iron is reduced to ferrous iron by hydroxylamine hydrochloride. At pH 2-~9, ferrous iron and o-phenanthroline form an orange-red complex. (3)
JB/T 7994-1999
This method develops color slowly below pH 2. When pH is above 3.5, color can be fully developed after 30 minutes of standing. Heating can accelerate color development. This method uses heating to develop color, and the color is stable.
5.2 Reagents
5.2.1 Sodium hydroxide (solid).
5.2.2 Hydrochloric acid (density 1.19).
5.2.3 Tartaric acid solution (5%).
5.2.4 Hydroxylamine hydrochloride solution (5%).
5.2.5 o-Phenanthroline solution (0.1%): Dissolve 0.1g o-Phenanthroline in 10mL 95% ethanol and dilute to 100mL with water. 5.2.6 o-Nitrophenol indicator (0.1%). 5.2.7 Ammonia water (1+1).
5.2.8 Hydrochloric acid (1+1).
5.2.9 Ferric oxide standard solution
a) Accurately weigh 0.1000g of ferric oxide (standard reagent) after drying at 110C for 2h into a 250mL beaker, add 40mL of hydrochloric acid (1+1), cover the surface with blood, heat to dissolve on a low-temperature sand bath, wait until it is completely dissolved, cool, transfer to a 1000mL volumetric flask, dilute to the mark with water, and shake to hook. This solution contains 0.1mg of ferric oxide per milliliter. b) Transfer 25mL of ferric oxide standard solution (0.1mg/mL) into a 250mL volumetric flask, add 2mL of hydrochloric acid (1+1), dilute to the mark with water, and shake to hook. This solution is a standard solution of ferric oxide containing 0.01mg per milliliter. 5.2.10 Blank solution: Weigh 10g of sodium hydroxide (solid) into a silver crucible, place it in a high-temperature furnace, heat it from room temperature to 700C and melt it for 5 minutes, take it out, cool it down, soak it in hot water in a 250mL beaker, immediately add 33mL of hydrochloric acid (density 1.19), heat and boil it for 5 minutes, transfer it to a 200mL volumetric flask, cool it down, dilute it to the scale with water, and shake it. 5.3 Drawing of working curve
Pipette 10mL of blank solution. 9 portions are placed in a group of 50mL volumetric flasks, and 0.00, 0.50, 1.00, 2.00, 3.00, 4.00.6.00, 8.00.10.00mL of ferric oxide standard solution (0.01mg/mL) are added in sequence. Add water to 25mL, add 5mL of alcoholic acid solution (5%) and 3mL of hydroxylamine hydrochloride solution (5%), shake it well, and put it in a flask. Leave for 3 minutes, add 2 drops of o-nitrophenol indicator (0.1%), adjust to yellow with ammonia (1+1), then adjust to yellow just disappear with hydrochloric acid (1+1), and add 3 drops in excess, add 5 ml of o-phenanthroline solution (0.1%), dilute to nearly 50 ml with water, heat in a boiling water bath for 5 minutes, take out, cool to room temperature with running water, dilute to scale with water, shake the hook, and measure its absorbance at 530 nm wavelength on a spectrophotometer with a 2 cm thick colorimetric III, using water as a reference. After subtracting the absorbance of the blank test, draw a working curve. 5.4 Analysis method
Pipette 25 ml of the test solution prepared in 4.4 into a 50 ml volumetric flask, add 5 ml of tartaric acid solution (5%) and 3 ml of hydroxylamine hydrochloride solution (5%), shake and let stand for 3 min, add 2 drops of o-nitrophenol indicator (0.1%), adjust to yellow with ammonia water (1+1), then adjust with hydrochloric acid (1+1) until the yellow disappears and 3 drops of excess, add 5 ml of o-phenanthroline solution (0.1%), dilute to nearly 50 ml with water, heat in a boiling water bath for 5 min, take out, cool to room temperature with running water, dilute to the scale with water, shake and use a 2 cm thick cuvette at a wavelength of 530 nm on a spectrophotometer, using water as a reference, and after subtracting the absorbance of the blank test, find the content of ferric oxide on the working curve. Calculate the percentage of ferric oxide according to formula (4): ml × 100%
w(Fe2O,)
g of ferric oxide obtained from the working curve, where: m,-—
m—mass of sample, g;
V-—total volume of test solution, mL;
,—volume of the test sample, ml.
5.5 Allowable error
The difference in analysis results between laboratories should not be greater than the allowable difference listed in Table 2, and the allowable difference within a laboratory should be less than the value shown in Table 2. 48
+( 4 )
Iron trioxide
0.11~0. 40
6 Determination of aluminum trioxide by chrome azuro blue S colorimetric method 6.1 Method summary
JB/T7994—1999
Allowance difference
In a weakly acidic solution, iron is masked with ascorbic acid. At pH 5.5, chrome azuro blue S forms a red-purple complex with aluminum. The absorbance of the color-developing solution is measured at a wavelength of 560 nm.
6.2'Reagents
6.2.1 Sodium hydroxide (solid).
6.2.2 Hydrochloric acid (density 1.19).
6.2.3 Hydrochloric acid (1+1).
Hydrochloric acid (1+9).
Ammonia water (1+1).
Methyl orange indicator (0.1%).
Hexamethylenetetramine solution (15%).
6.2.8Ascorbic acid solution (1%, freshly prepared). 6.2.9Chrome azuro blue S solution (0.03%): weigh 0.03 chrome azuro blue S, add 20 mL of water, and then add 80 mL of ethanol. 6.2.10Aluminum standard solution (each mL contains 1 mg of lead trioxide): weigh 0.2646 g of metallic aluminum (99.99%) into a 250 mL beaker, add a small amount of water, add 20 mL of hydrochloric acid (1+1), heat until completely dissolved, cool to room temperature, transfer to a 500 mL container bottle, dilute to the mark with water, and shake to check.
6.2.11 Aluminum standard solution (containing 0.01 mg of aluminum oxide per milliliter): Transfer 5 mL of aluminum standard solution (1 mg/ml) to a 500 mL volumetric flask, dilute to the mark with water, and shake well. 6.2.12 Blank solution: Weigh 8 g of sodium hydroxide and place it in a silver crucible. Melt it in a 700°C high-temperature furnace for 10 minutes. Take it out, cool it, extract it with hot water, and place it in a 250 mL beaker. Add 25 mL of hydrochloric acid (density 1.19), heat and boil it for 5 minutes, cool it, transfer it to a 200 mL volumetric flask, dilute to the mark with water, and shake well.
6.3 Drawing of working curve
Take nine portions of 10 ml of blank solution and place them in a group of 50 mL volumetric flasks. Add aluminum standard solution (0.01 mg/mL) at 0, 0.5, 1.0, 1.5, 2.03, respectively.0.4.0.5.0,6.0mL, add 1 drop of methyl orange indicator (0.1%), neutralize with ammonia water (1+1) to yellow, then adjust with hydrochloric acid 1+9) until the solution turns red, then add 2.0ml in excess, add 1ml of ascorbic acid (1%), accurately add 5mL of chrome azuro blue S (0.03%), shake well, then add 10mL of hexamethylenetetramine (15%), dilute with water to the scale, shake to hook, use 0.5cm thick colorimetric III at a wavelength of 560nm on the spectrophotometer, use water as a reference to measure the absorbance, subtract the absorbance of the blank test, and draw a working curve. 6.4 Analysis method
Take 10.00～20.00ml of the test solution prepared in 4.4 and put it into a 50ml volumetric flask. Add 1 drop of methyl orange indicator, neutralize with ammonia water (1+1) to yellow, and then adjust with hydrochloric acid (1+9) until the solution just turns red, with an excess of 2.0mL. Add 1mL of ascorbic acid (1%), accurately add 5mL of chrome azuro blue S (0.03%), shake the spoon, and then add 10mL of hexamethylenetetramine (15%), dilute with water to the scale, shake well, and measure its absorbance at a wavelength of 560nm on a spectrophotometer with a 0.5cm thick colorimetric blood, using water as a reference. After subtracting the absorbance of the blank test, find the aluminum oxide content on the working curve. Calculate the percentage of aluminum oxide according to formula (5): W(Al,O,)
×100%
Wherein: mi-
JB/T 7994-1999
aluminum oxide amount found on the working curve + name, sample weight, g;
V——total volume of test solution, mL
Vi——volume of test solution taken, mL.
6.5 Allowable error
The difference between the analysis results of laboratories should not be greater than the allowable difference listed in Table 3, and the allowable difference within a laboratory should be less than the value shown in Table 3. Table 3
Aluminum trifluoride
0. 11 ~0. 50
7 Determination of calcium oxide
7.1 Method summary
Tolerance
In a solution with a pH of 8 to 13, calcium ions react with EDTA to form a colorless complex. At pH 13, calcium ions react with sodium salt of calcium reagent hydroxy acid to form a red complex, in which calcium ions can be captured by EDTA, and the indicator is released to form a pure blue color. This indicates the end point and can determine the calcium content.
After separating calcium and magnesium from most metal ions with hexamethylenetetramine-copper reagent, adjust the pH to 13, use sodium salt of calcium reagent hydroxy acid as an indicator, and titrate calcium with EDTA standard solution. At this time, magnesium ions form Mg (OH) + or Mg (OH): precipitation, which does not react with EDTA and therefore does not interfere with the determination.
7.2 Reagents
Sodium hydroxide (solid).
Hydrochloric acid (density 1.19).
Hydrochloric acid (1+1).
Ammonia water (11).
Methyl red indicator (0.1%).
Hexamethylenetetramine (15%).
Copper reagent (solid).
Sodium hydroxide solution (20%).
Calcium reagent sodium hydroxide salt indicator (1:100): Weigh 0.5g of calcium reagent sodium hydroxide and 50g of sodium fluoride, grind them thoroughly and mix. 7.2.10 EDTA standard solution (0.01M). a) Weigh 3.75g of EDTA in a 400mL beaker, add 200mL of water, heat at low temperature to dissolve, cool and filter into a 1000mL volumetric flask, dilute to the mark with water, and shake. b) Calibration:
Accurately weigh 1.7848g of calcium carbonate (reference reagent) after baking at 110C for 2h in a 250ml beaker, add 50mL of water, add hydrochloric acid (1+1) until completely dissolved, and add 2-3 drops in excess, heat and boil to drive out carbon dioxide, cool and transfer to a 1000mL volumetric flask, dilute to scale with water, and shake well. This solution is the calcium oxide standard solution (containing 1mg of calcium oxide per milliliter). Take 10mL of calcium oxide standard solution in a 300ml conical flask, add 100mL of water, add 10mL of sodium hydroxide (20%), shake well, add a small amount of calcium reagent and sodium acid salt indicator, and titrate with the prepared EDTA standard solution until pure blue is the end point, and do a blank test under the same conditions.
Calculate the titer of EDTA standard solution against calcium oxide and magnesium oxide according to formula (6) and formula (7): Too=
Wherein: m--
Mass of calcium oxide·nm;
JB/T 7994—1999
TMgo t 0. 718 8Tca0
The volume of EDTA standard solution consumed during titration (blank value has been subtracted), mI; The titer of EDTA standard solution against calcium oxide, g/mL.; -The coefficient for converting CaO to MgO.
7.3 Preparation of test solution
Accurately weigh 0.2000g of sample into a silver crucible, add 4g of sodium hydroxide, cover the crucible and put it into a high-temperature furnace, heat from room temperature to 700℃, melt at this temperature for 10-15min, take it out, rotate the crucible to make the molten material adhere to the inner wall of the crucible, cool it, pump it with hot water and put it into a 250ml beaker, add 10mL of hydrochloric acid (density 1.19) and boil it for 5min, cool it, transfer it into a 250mL volumetric flask, add 1 drop of methyl orange indicator, adjust it to yellow with ammonia water (1+1), and then adjust it to red with hydrochloric acid (1+1), add 5mL of hexamethylenetetramine (15%), add 0.1g of copper reagent, dilute to the scale with water, shake it thoroughly, dry filter it with quick filter paper into a dry beaker for the measurement of CaO and MgO. 7.4 Analytical method
Pipette 100mL of the test solution prepared in 7.3 into a 250mL conical flask, add 10mL of sodium hydroxide (20%), shake well, add a small amount of calcium reagent sodium salt indicator, shake well, and slowly titrate with 0.01M EDTA standard solution until pure blue is the end point, and perform a blank test under the same conditions.
Calculate the percentage of calcium oxide according to formula (8): (CaO)
Where: V—
VTc × 100%
The volume of EDTA standard solution consumed during titration (blank value has been subtracted), mI; Tcao—-the titer of EDTA standard solution on calcium oxide + g/mI.m
Weigh the sample mass, g;
V,——-the total volume of the test solution, mL,
V,—the volume of the test solution taken, mL.
7.5 Allowable error
The difference between the analysis results of laboratories should not be greater than the allowable error listed in Table 4, and the allowable error within a laboratory should be less than the value shown in Table 4. Table 4
Calcium oxide
0. 51～1. 00
8 Determination of magnesium oxide
8.1 Method summary
Allowable error
(8)
In a solution of pH 8～10, calcium and magnesium ions can quantitatively form a colorless complex with EDTA. In an ammonia buffer solution of pH 10, calcium and magnesium ions can form a purple-red complex with the complex indicator, in which calcium and magnesium ions can be captured by EDTA, and the free indicator is pure blue, which indicates the end point and can be used to determine the magnesium oxide content. After separating calcium and magnesium from most metal ions with hexamethylenetetramine-copper reagent, adjust the pH to 10, use EDTA standard solution to titrate the calcium and magnesium content with EDTA as an indicator, and obtain the magnesium content after subtracting the calcium. 8.2 Reagents
8.2.1 Ammonium chloride-ammonium hydroxide buffer solution (pH 10): weigh 67.5g of ammonium fluoride and dissolve it in 250mL of water, add 570ml of ammonium hydroxide, and dilute to 1000ml with water. 8.2.2 EDTA indicator (1+100): weigh 0.5g of EDTA and 50g of sodium chloride, grind them into fine powder, and mix. 51
JB/T7994—1999
8.2.3 EDTA standard solution: 0.01M (see 7.2.10). 8.3 Analysis method
Put 100mL of the test solution prepared in 7.3 into a 250mL conical flask, add 10ml of ammonium fluoride-ammonium hydroxide buffer solution, add a small amount of EDTA indicator, shake the hook, and titrate with 0.01M EDTA standard solution until pure blue is the end point, which is the total amount of calcium and magnesium. Perform a blank test under the same conditions.
Calculate the percentage of magnesium oxide according to formula (9): (VL-V)TM ×100%
(MgO) =
Wherein, V
The volume of EDTA standard solution consumed when titrating calcium (the blank value has been subtracted), mLV, —-The volume of EDTA standard solution consumed when titrating calcium and magnesium (the blank value has been subtracted).mL; TMo-
The titer of EDTA standard solution on magnesium oxide·g/mL; The mass of the sample, g;
The total volume of the test solution, ml;
The volume of the test solution taken, mL
8.4 Allowable error
The difference between the analysis results of laboratories shall not be greater than the allowable error listed in Table 5, and the allowable error within a laboratory shall be less than the value shown in Table 5. Table 5
Magnesium oxide
1.00--3.00
3. 01-~ 5.00
5. 01 ~~8. 00
Allowable error
(９))
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