JB/T 4394-1999 Chemical analysis method for total rare earth content, silicon and magnesium in rare earth magnesium alloys
Some standard content:
JB/T4394-1999
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This standard is a revision of JB4394-87 "Chemical Analysis Methods for Total Rare Earth, Silicon and Magnesium in Rare Earth Magnesium Alloys". During the revision, editorial changes were made to the original standard, and the main technical content remained unchanged. This standard replaces JB4394--87 from the date of implementation. This standard is proposed and administered by the National Casting Standardization Technical Committee. The drafting unit of this standard is: Wuxi Diesel Engine Factory and other units. The main drafters of this standard: Ling Shurong et al., 351
Scope
Mechanical Industry Standard of the People's Republic of China
Rare Earth Magnesium Alloys
Chemistry of Rare Total Amount, Silicon and Magnesium Analysis method Chemical analysis mnethods for total rare-earth, silicon, magnesiun in rare-earth magnesiumt alloysJB/T 4394
1999
instead of JB4394-87
This standard specifies azo chlorine Lin II photometric method, oxalate gravimetric method, azochlorine 1 photometric method and copper reagent separation EDTA complex titration method and other methods.
This standard is applicable to the determination of total rare earth content, silicon and magnesium in rare earth magnesium alloys (i.e. spheroidizing agent). This standard complies with (GB/T1467. 2 Reference Standards
The provisions contained in the following standards constitute provisions of this standard through reference in this standard. When this standard is published, the versions indicated are valid. All The standards will be revised, and all parties who use this standard should explore the possibility of using the latest version of the following standards: GI3/T1467~-1978 General principles and general provisions of the standard for chemical analysis methods of metallurgical products GB/T4333.1--- 1984 Chemical analysis method of ferrosilicon Determination of silicon content by perchloric acid dehydration gravimetric method 3 Determination of total rare earth content by azofat Ⅱ photometric method 3.1 Determination range: 1% ~ 10%,
3.2 Method summary
The sample (must pass through a 140-mesh screen) is dissolved in a plastic beaker with nitric acid and hydrofluoric acid. Boric acid complexes fluoride ions, and rare earths and azochlorofluoride form a blue-green complex. 3.3 Reagent ||tt ||3.3.1 Nitric acid (density 1.42g/mL).
3.3.2 Nitric acid (1+5).
3.3. Hydrofluoric acid (density 1.15g/ml). 4. Boric acid solution (4%).
Oxalic acid solution (2.5%): 25g oxalic acid dissolved in appropriate amount of water, add 50mL nitric acid (3.3.1), dilute with water to 1000ml, 3.3.5
Mix well.
3.3.6 Azochloride solution (0.04%). 3.3.7 Rare earth standard solution:
Weigh 0.1198g rare earth oxide (more than 99.9%, preheated at 850℃ Burn, cool), add 10ml hydrochloric acid (density 1.19g/ml.) into a 100mL beaker, heat to dissolve, transfer to 1000ml volumetric flask, dilute to volume with water, mix and transfer 50.00ml. In the measuring bottle, add 10ml of nitric acid (3.3.2). Dilute to the mark with water and mix well. 1mL of this solution contains 54g of rare earths. Note: Rare earth oxides refer to Baotou minerals. Rare earth oxides are converted into total metal rare earths. The conversion factor is 0.835. The conversion factor for minerals in other regions should be calculated based on actual data
National Machinery Industry Bureau approved 352 on 1999-06-24
Implemented on 2000-01-01||tt ||3.3.8 Hydrochloric acid (0.1N)
JB/T4394-1999
1-Benzene-3-methyl-4-benzoyl-pyrazolone-[5J(PMBP) -Benzene solution: Weigh 0.2783g PMBP and dissolve it in 100ml of benzene. 3.3.9
3.4 ??Analysis steps
3.4.1 Sample amount
Weigh the sample amount according to Table 1. .
Table
Thin
3.4.2 Blank test
%
1. 00 ~-4. 00
4. 00 -~ 10. 00
Use the rare earth-free ferrosilicon standard sample to do a blank test with random samples. 3.4.3 Measure
Test
0.2500
0.100
3.4.3.1 Weigh the sample into a plastic beaker, add 6ml of nitric acid (3.3.1), Use a plastic dropper to add 4 mL of hydrofluoric acid (3.2.3) while shaking. After the sample is dissolved, add 50 mL of boric acid solution (3.3.4). Mix and leave for 10 minutes. Transfer it to a 100 mL volumetric flask and add water to it. Dilute to volume and mix.
Transfer 5.00ml test carboxylic acid into a 100ml volumetric flask, add 5mlL nitric acid (3.3.2), dilute with water to the mark, and mix. 3.4.3.2 Sample without needle
a) Pipette 5.00mlL test solution (3.4.3.1) into a 25ml volumetric flask, add 5ml oxalic acid solution (3.3.5) and 5ml azo chloride Lin III solution (3.3.6), dilute with water to the mark, mix well, transfer part of the solution to 3cm for colorimetry, use the blank test as a reference, and measure the absorbance at a wavelength of 680mm on a spectrophotometer. || tt | Solution (3.3.7), 5 mL oxalic acid solution (3.3.5), 5 ml chlorophosphine azozoate II solution (3.3.6). Dilute to volume with water and mix. Transfer part of the solution into 3cm colorimetric blood, use the blank test as a reference, measure the absorbance at a spectrophotometer wavelength of 680nm, and draw a working curve with the total amount of rare earth as the abscissa and the absorbance as the ordinate. 3.4.3.3 Sample containing needle
a) Pipette 5.00ml of test solution (3.4.3.1) into a 50mL beaker, heat and evaporate until nearly dry, cool, add 5ml of hydrochloric acid (3.3.8), and make sure Dissolve the salts, move them into a 60mL separatory funnel, add 5.0mL PMBP-benzene solution (3.3.9), vibrate for 1 minute for extraction, after layering, put the aqueous phase into a 25mL volumetric flask, and then add 5.0mL hydrochloric acid (3.3.3. 8) Wash the beaker, pour the organic phase into it, shake for a second time for 1 minute, after layering, combine the aqueous phase into a 25mL volumetric flask, then add 5ml of oxalic acid solution (3.3.5) and 5ml of azofluorin III solution ( 3.3.6), dilute with water to the mark and mix. Transfer part of the solution into a 3cm cuvette, use the blank test as a reference, and measure the absorbance at a wavelength of 680nm on a spectrophotometer.
b) Pipette 7 portions of 5.00mL blank test solution, add 0.00.0.50, 1.00, 2.00, 3.00.4.00, 5.00mL rare earth standard solution (3.3.7) respectively into the 50mL beaker, follow this article Carry out item a), measure the absorbance, and draw a working curve. 3.5 Calculation of analysis results
Calculate the percentage of total rare earth content according to formula (1): RE-㎡×100%
In the formula: m1---the total rare earth content found on the working curve Large amount; sample size·g.
3.6 metric
353
JB/T4394--1999
The difference in analysis results between laboratories should not be greater than the tolerance listed in Table 2, use standard samples The calibration shall not exceed 1/2 of the tolerance listed in Table 2. Table 2 | | tt |
4.1 Measuring range: 5% ~ 40%.
4.2 Method summary
public
o. 20
0.40
difference
The sample is treated with nitric acid and hydrofluoride in a plastic beaker Dissolve the acid, evaporate it to dryness in a boiling water bath, then transfer it to a glass beaker and use sulfuric acid to remove the fluorine, separate the interfering ions through ammonium suboxide, add oxalic acid, and precipitate the rare earth into oxalic acid in an acidic solution with a pH of 1.5 to 2.0. , and burned into rare earth oxide, weighed.
The interference of the needle is deducted from the calculation after measuring the oxidized needle by photometry. 4.3 Reagents
4.3.1 Nitric acid (density 1.42g/ml).
Hydrofluoric acid (density 1.15g/mL).
4.3.2
4.3.3
Sulfuric acid (1+1).
4.3.4
Ammonium hydroxide (1+1).
4.3.5
Ammonium hydrochloride (1+4).
Boric acid solution (4%).
4.3.6
4.3.7
4.3.8
4.3.9
Hydrochloric acid (1+1).
Hydrochloric acid (1+4).
Hydrochloric acid (1+19).
4.3.10
4.3.11
4.3.12
4.3.13
4.3.14
4.3.15|| tt||4.3.16
4.3.17
4.3.18
4.3.19
Hydrochloric acid (0.225N).
Ammonium fluoride lotion (2%): Adjust to pH 10 with ammonium hydroxide (1+1). Oxalic acid-ammonium oxalate mixed lotion: Mix equal volumes of oxalic acid solution (1.5%) and ammonium oxalate solution (1%). Oxalic acid solution (10%).
Hydrogen peroxide (1+9).
Hydrogen peroxide (density 1.10g/mL).
Ascorbic acid solution (2%).
Tartaric acid solution (5%).
p-nitrophenol indicator (0.5%).
AZO solution (0.2%).
4.3.20
Chloroacetic acid buffer solution (pH1.7): Weigh 87g of monochloroacetic acid and dissolve it in 200ml of water. Adjust ammonium hydroxide (1+1) to pH 1.7 (measured with a pH meter)
4.3.21 Oxidation needle standard solution
Weigh 0.2106g Th nitric acid (NO) (*4H201). 99.9% or above) in a 200mL beaker, add a small amount of water to dissolve, add 10ml hydrochloric acid (density 1.19g/ml.) and evaporate to dryness, add 25ml hydrochloric acid (density 1.19g/ml.) to dissolve, transfer to 1000ml Volumetric flask 4, dilute to the mark with water, mix, transfer 50.00mL to 500mL. Volumetric flask, dilute to the mark with water, mix, 1mL of this solution contains 10 μg of oxidized t.
4.4 Analysis steps||tt| |4.4.1 Sample quantity
354
Weigh 0.5000g sample
4.4.2 Blank test
JB/T4394-1999
Use the ferrosilicon standard sample that does not contain rare earths to perform a blank test together with the sample to be tested. 4.4.3 Measurement
4.4.3.1 Weigh the sample into a plastic beaker, add 3 mL of nitric acid (4.3.1), and add 5 ml dropwise. .Hydrofluoric acid (4.3.2), after the sample is dissolved, evaporate to dryness on a boiling water bath, add 6mL of sulfuric acid (4.3.3), transfer to a 300ml glass beaker, steam until the stomach sulfuric acid is white, and cool. , rinse the wall of the cup with water, then heat until white smoke of sulfuric acid is emitted, cool, rinse the wall of the cup with water, add 20ml of hydrochloric acid (4.3.7), heat to dissolve the salt, add 100ml of water, and boil.
4.4.3.2. Neutralize with ammonium hydroxide (4.3.4) until the hydroxide precipitates out, with an excess of 20 mL, heat to boil, cool slightly, wait until the precipitate sinks, filter with rapid quantitative filter paper while hot, and wash with hot ammonium chloride (4.3.11) Wash the beaker 2 times and precipitate 4 times. Discard the filtrate. 4.4.3.3 Add hot hydrochloric acid (4.3.7) to the funnel in portions to dissolve the precipitate in the original beaker. Precipitate again as per 4.4.3.2. Use Wash the beaker with ammonium chloride washing solution (4.3.11) 3 to 4 times and precipitate 6 to 7 times. 4.4.3.4 Add hot hydrochloric acid (4.3.7) to the funnel in batches to dissolve the precipitate in the original beaker. Wash the filter paper with hydrochloric acid (41.3.9) and hot water, heat the solution to boil, add hot water to about 100mL, add 50mL oxalic acid solution (4.3.13), and adjust the PpH1 with ammonium hydroxide (4.3.4). 5~2.0 (test with precision pH paper), boil, keep at 80C for 10 minutes, leave at room temperature for more than 2 hours, filter with dense quantitative filter paper, wash with 2~3ml of oxalic acid-ammonium oxalate mixed washing solution (4.3.12) each time. Beaker 3~~4 times, sedimentation 10~12 times. 4.4.3.5 Place the sedimentation and filter paper into the constant weight porcelain, ashes it at low temperature, then burn it in a high temperature furnace at 850C for 40 minutes, take it out and put it in a desiccator. Cool, weigh, and burn to constant weight. 4.4.3.6 Determination of oxidized needles in rare earth oxide precipitation a) Place the constant weight rare earth oxide in a 100mL beaker, add 5ml hydrochloric acid (4.3.7) and a few drops of hydrogen peroxide (4.3.14). Dissolve by heating at low temperature, cool to room temperature, transfer to 50mL volumetric flask, dilute to volume with water, and mix. b) Transfer 5.00mL of the test solution [a) of this article into a 25mL volumetric flask, add 2mL of ascorbic acid solution (4.3.16), 1mL of alcoholic acid solution (4.3.17), mix well, and add 2 drops of p-nitrophenol Indicator (4.3.18), adjust to yellow with ammonium hydroxide (4.3.4), adjust to colorless with hydrochloric acid (4.3.7), add 2ml. Hydrochloric acid (4.3.10), 2.5mL monochloroacetic acid buffer Dilute the solution (4.3.20) and 2mL of azo 1 solution (4.3.19) with water to the mark and mix. Transfer part of the test solution into a 3cm colorimeter, use the reagent blank as a reference, and measure the absorbance at a wavelength of 590 nm on a spectrophotometer.
c) Working curve drawing
Pipette 0.00, 1.00, 2.00, 8.00mL oxidation standard solution (4.3.21) and place them in a series of 25ml volumetric flasks respectively, according to item b) of this article Carry out color development, measure its absorbance, and draw a working curve with the amount of oxidized needles as the abscissa and the absorbance as the ordinate. 4.5 Calculation of analysis results
Calculate the percentage of total rare earth content according to formula (2): RE= (mlm2ma)×0.835
m
Where: ||tt ||m
m2
m
0.835
The mass of rare earth oxides and oxidized needles, name; the mass of oxidized needles + tolerance,
Blank Mass·8;
Sample quantity·name t
Conversion factor for converting rare earth oxide into total rare earth quantity. X100% | | tt | Or directly report the percentage content of rare earth oxides, 4.6 tolerance
The difference in analysis results between laboratories should not be greater than the tolerance listed in Table 3, and the tolerance listed in Table 3 should not be exceeded when using standard samples for calibration 1/2.
355
Determination of silicon content
5
Total rare earth content
5.00～10.00
>10. 00--20. 00
>20. 00~~30. 00
30 00
JB/T 4394.-1999
Table 3
5.1 Gravimetric determination The amount of silicon is in accordance with GB/T4333.1. Note: The sample must pass through a 140 mesh screen.
Determination of silicon content by volumetric method, according to this standard potassium fluorosilicate volumetric method, measuring range: 25% 50%. 5.2 Method summary
public
0.40
0.50
0.60
0.70
Sample (must pass 140 mesh screen) with nitric acid , dissolve hydrofluoric acid to convert silicon into fluorosilicic acid, add potassium nitrate to precipitate potassium fluorosilicate, after filtering, neutralize the free acid with sodium hydroxide, then add boiling water to hydrolyze potassium fluorosilicate. To release hydrofluoric acid, titrate with sodium oxyoxide standard solution.
If there is acid-insoluble matter during dissolution, it should be melted with alkali, and then the amount of silicon in the insoluble matter should be measured photometrically and added to the result obtained by volumetric method.
5.3 Reagent
5.3.1 Nitric acid (density 1.42g/mL).
5.3.2
Hydrofluoric acid (density 1.15g/ml), excellent grade pure. Hydrogen peroxide (density 1.10g/mL).
5.3.3
5.3.4 Saturated solution of potassium nitrate.
Tartaric acid-urea mixture: Weigh 20g tartaric acid and 10g urea and dissolve them in 100mL water. 5.3.5
Potassium nitrate lotion: Weigh 10g of potassium nitrate and dissolve it in 90ml of water, add 10mL of ethanol, and mix well. 5.3.6
5.3.7
Phenolic viscosity indicator (1%): Weigh 1g of phenolic acid and dissolve it in 60mL of ethanol, dilute to 100ml with water, and mix. 5.3.8 Neutral water: Boil the water for 15 minutes, add 1 drop of phenolic acid indicator, and add sodium hydroxide standard solution dropwise to neutralize to a stable reddish color. 5.3.9 Sodium hydroxide standard solution (0.1500N) Weigh 6g of high-grade pure sodium hydroxide in a 1000mL beaker, dissolve it in water, add 0.14g of vanadium chloride, and boil it to drive out the sodium hydroxide. 5.3.9.1
Dissolve carbon dioxide in cold water to 1000 mL, let it stand for complete precipitation, then add 0.05g sodium sulfate, mix, let stand for one day, take the clear liquid, store it in a plastic bottle, and use it after calibration. 5.3.9.2 Calibration: Weigh 4 parts of 1.5000g of potassium hydrogen phthalate (standard reagent) dried at 120°C for 1 hour in a 250mL beaker, add 100mL of cold water that has been boiled to remove carbon dioxide, warm to dissolve, and add 1 drop Phenolic indicator, titrate with sodium oxyhydroxide standard solution until the end point is reddish. The range of titrated milliliters does not exceed 0.1, take the average value, and calculate the concentration of sodium hydroxide standard solution according to formula (3): VX0.2042
where: N
sodium hydroxide standard Normality of the solution; V - volume of sodium hydroxide standard solution consumed, mL; - mass of potassium hydrogen phthalate, g:
0.2042 --- milligram equivalent of potassium hydrogen phthalate 5.3.10 Mixed solvent: Mix equal amounts of anhydrous sodium carbonate and anhydrous potassium carbonate. 5.3.11 Hydrochloric acid (1+1).
5.3.12 Sulfuric acid (5+995).
356
(3)
5.3.13 ammonium acid solution (5%).
JB/T 4394--1999
5.3.14 Oxalic acid solution (2%): Weigh 20g of oxalic acid and dissolve it in an appropriate amount of water, add 100ml of sulfuric acid (density 1.84g/mL.), Dilute with water to 1000ml
5.3.15 Ferric ammonium sulfate solution (6%): Weigh 6g ferrous ammonium sulfate, add appropriate amount of water and 1mL sulfuric acid (density 1.84g/ml.), dissolve and dilute to 100mLc
5.3.16 Silicon standard solution: weigh 0.4279g carbon monoxide (more than 99.9%, pre-burned at 1000°C for 1 hour and then placed in a desiccator, cooled to room overflow), add 3g of anhydrous carbonic acid Put the sodium in a platinum crucible, and cover it with 1~~2g of anhydrous sodium carbonate. Heat the platinum crucible at a low overflow place first, and then place it at a high temperature of 950°C to heat and melt until it is transparent. Keep it for 30 minutes, take it out, cool it, and use Dip the frit into a plastic cup of cold water until it is completely dissolved. Take out the pot, scrub it carefully, cool it to room temperature, transfer it to a 1000ml volumetric flask, dilute it with water to the mark, and mix well. Pipette 100.00ml, place the above solution into a 1000mL volumetric flask, dilute to volume with water, mix, and store in a plastic bottle. 1ml of this solution contains 20μg of silicon.
5.4 Analysis steps
5.4.1 Sample amountwww.bzxz.net
Weigh 0.1000g sample.
5.4.2 Blank self-test
Do a blank test along with the sample.
5.4.3 Determination
5.4.3.1 Weigh the sample into a plastic beaker, add 10mL nitric acid (5.3.1), shake while dropping, and add 5mL hydrofluoric acid (5.3. 2) After the sample is dissolved, add 4 to 5 drops of hydrogen peroxide (5.3.3) to mix, leave it for 10 minutes, filter it in a plastic funnel with quantitative filter paper, wash the precipitate with water 5 to 6 times, and control the volume of the filtrate at 70 mL. Within), use a 400mL plastic beaker. Note: The temperature should be controlled above 40℃ during dissolution. 5.4.3.2 Add 5 ml of tartaric acid-urea mixture (5.3.5) to the filtrate (5.4.3.1), mix well, add a little filter paper pulp, add 30 ml of saturated potassium nitrate solution (5.3.4), stir for 1 minute, and drain. Cool to room temperature, place for 10~~15min (in cold water in summer), filter with a plastic funnel and quantitative filter paper, wash the plastic beaker 3~4 times with potassium nitrate washing solution (5.3.6), and wash the sediment 5~6 times. Move the precipitate and filter paper into the original plastic beaker, add 15ml potassium nitrate washing solution (5.3.6), 5 drops of phenolic acid indicator, neutralize most of the acid with sodium hydroxide standard solution (5.3.9) and stir again Shred the filter paper and titrate carefully until a stable reddish color appears. The volume of sodium hydroxide standard solution consumed is not calculated. 5.4.3.3 Add 200ml of boiled neutral water (5.3.8), and titrate immediately with sodium hydroxide standard solution (5.3.9). When approaching the end point, add another 10 drops of phenolic acid indicator (5.3.7) , continue titrating to a stable reddish color as the end point. Note: The temperature should be controlled above 60℃ during titration. 5.4.3.4 Determination of silicon in insoluble matter
a) Transfer the filter paper and precipitate (5.4.3.1) into a nickel crucible, ashes, burn in a high temperature furnace at 850C for 30 minutes, take out and cool, add 2g of mixed solvent (5.3.10), stir evenly, cover, heat at low temperature first, then place at 850C high temperature to melt for 10-20 minutes, take out and cool, pour out with water, wash the pot, add 20mL hydrochloric acid (5.3.11) to acidify , transfer to a 200mL volumetric flask, dilute to volume with water, and mix. b) Pipette two portions of 5.00ml test solution and place them in 100mL volumetric flasks respectively. Add 5ml sulfuric acid (5.3.12) and 5ml ammonium aluminate solution (5.3.13) to each portion of the test solution, and place in a boiling water bath Heat for 25 seconds, add 25 mL oxalic acid solution (5.3.14), 5 mL ferrous ammonium sulfate solution (5.3.15), dilute to volume with water, and shake well. This liquid is a chromogenic liquid. In another test solution, add 5 mL sulfuric acid (5.3.12), 25 mL oxalic acid solution (5.3.14), 5 mL ammonium molybdate solution (5.3.13), and 5 mL ferrous ammonium sulfate solution (5.3.15). , dilute to volume with water and mix well. This liquid is the compensation liquid. Transfer part of the test solution into 3cm colorimetric blood, use the compensation solution as a reference, measure its absorbance, subtract the absorbance of the reagent blank, and find the corresponding silicon amount on the working curve.
c) Drawing of working curve
Pipette 7 copies of 5.00mL blank test and place them in 100mL volumetric flasks. Add 0.00, 1.00, 2.00, 3.00, 4.00, 5.00 to 6 of them respectively. ml silicon standard solution (5.3.16), and the other part is used as the compensation solution, all are carried out according to item b) of this article, measure the absorbance, and subtract the test 357
JB/T 4394 -1999
After measuring the absorbance of the agent blank, draw a working curve with the silicon amount as the abscissa and the absorbance as the ordinate. 5.5 Calculation of analysis results
5.5.1 Calculate the percentage content of silicon measured by the volumetric method according to formula (4): Sit?
(VV,)NX0. 007022
X100%
Where: V.—the volume of sodium hydroxide standard solution consumed by one titration, mL; V. .Volume of blank oxygen-consuming sodium oxide standard solution, mL; Normality of N sodium hydroxide solution;
Sample volume,:
0.007022-
Milligram equivalent of silicon· g.
5.5.2 Calculate the percentage content of silicon in the insoluble matter according to formula (5): Si,
where: V
total volume of test solution mL;
V.---Dispense the volume of the test solution, mL;
The amount of silicon found on the working curve + g;
m.-
m·Sample volume.g.
5.5.3 Calculate the total silicon content in the sample according to formula (6): m.
my
X100%
Si(%)=S(%) +Si2(%)
.(4)
(5)
(6)
5.6 Tolerance
Difference in analysis results between laboratories Values ??should be no greater than the tolerances listed in Table 4. When using standard specimens for calibration, it shall not exceed 1/2 of the tolerances listed in Table 4. ||6 Azofluorine "Photometric determination of magnesium content
6.1 Determination range: 1% ~ 5%.
6.2 Method summary
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difference|| tt | It forms a purple-red complex with azochlorine 1. The amount of magnesium in the chromogenic solution is less than 150 mg, aluminum is less than 30 pg, titanium is less than 30 μg, manganese is less than 30% soap, and calcium is less than 30%. 30ug, copper is less than 30ug, which does not affect the measurement. The interference of rare earth can be eliminated by leaving it for 10 minutes after color development. 6.3 Reagents
6.3.1 nitric acid (density 1.42g/ml.). 6.3.2
Nitric acid (1→5).
Hydrofluoric acid (density 1.15g/ml).
6.3.3
6.3.4 Boric acid solution (4%).
6.3.5 Triethanolamine (1+6).
6.3.6 Borax buffer (pH10): Weigh 21g borax (Na.BO, 10H.0) and 4g sodium hydroxide. After dissolving, dilute 1000ml with water and mix.
6.3.7 EGTA-Pb solution: Weigh 1.9g ethylene glycol bis (α-aminoethyl) ether tetraacetic acid (EGTA) and 1.8g lead nitrate, add 90ml borax buffer to 200ml water. (4.3.6), heat to dissolve, dilute with water to 1000ml., mix well. 358
6.3.8 Azochlorophosphine 1 solution (0.025%). 6.3.9 EDTA solution (5%).
6.3.10 magnesium standard solution
JB/T 4394--1999
Weigh 0.1659g magnesium oxide (more than 99.9%), burn it at 850C for 30 minutes, and put it in a desiccator Cool to room temperature), place: Add 10mL hydrochloric acid (1 + 1) to a 200ml beaker, heat to dissolve, cool, transfer to a 1000mL volumetric flask, dilute to volume with water, and mix. Pipette 20.00mL into a 1000mL volumetric flask, dilute with water to the mark, mix with a spoon and add 1ml of this solution. Contains 2ug magnesium. 6.4 Analysis steps
6.4.1 Sample amount
Weigh 0.1000g sample.
6.4.2 Blank test
Do a blank test with the magnesia-free standard sample along with the sample. 6.4.3 Determination
6.4.3.1 Weigh the sample into a plastic beaker, add 6ml of nitric acid (6.3.1), and add 1ml of hydrofluoric acid (6.3.3) while shaking with a plastic dropper. ), after the sample is dissolved, add 50ml boric acid solution (6.3.4), mix well, leave it for 10 minutes, transfer it to a 100ml volumetric flask, dilute it with water to the mark, and mix.
6.4.3.2 Pipette 10.00mL test solution (6.4.3.1) into a 100ml volumetric flask, add 5ml nitric acid (6.3.2), dilute to the mark with water, and mix.
6.4.3.3 Pipette 2.00mL of test solution (6.4.3.2) (magnesium content is less than 2%, pipette 5mL), place it in a 50ml volumetric flask, add 5ml of triethanolamine (6.3.5 ), mix, leave for 5 minutes, add 1ml of EGTA-Ph solution (6.3.7), 5ml of borax buffer (6.3.6), 5ml of azophosphine I solution (6.3.8), and dilute to the mark with water. Mix well. After leaving it for 10 minutes, transfer part of the test solution into a 3cm colorimetric ml, and add 2 drops of EDTA solution (6.3.9) to the remaining solution for reference after fading. Measure the absorbance at a spectrophotometer wavelength of 580mm, subtract the absorbance of the blank test, and find the corresponding magnesium amount on the working curve. 6.4.3.4 Drawing of working curve
Pipette 2.00mL (magnesium content is less than 2%, pipette 5mL) 8 portions of blank test solution into a 50ml volumetric flask, add (), 000.50, 1.00. 2.00, 3.00, 4.00.5.00, 6.00ml. Magnesium standard solution (6.3.10). In the analysis steps, add triethanolamine and other reagents in sequence according to 6.4.3.3, dilute with water to the mark, measure the absorbance, subtract the absorbance of "0.00ml.\", use the magnesium amount as the abscissa and the absorbance as the ordinate, draw the work Curve.
6.5 Calculation of analysis results
Calculate the percentage of magnesium according to formula (7):
Mg:
”~ total volume of test solution, mL;
Wuzhong: V
V
Divide the test solution volume, mL;
m
m
6.6 tolerance||tt ||The amount of magnesium found on the working curve is too much;
The sample amount.
m,
nV
X100% ·
The analytical value between laboratories should be greater than the tolerance listed in Table 5. When using a standard sample for calibration, it shall not exceed 1/2 of the tolerance listed in Table 5 Table 5
Magnesium content
1.00~2.00
>2.00~5.00
Public
Difference
0.20
%
359
6 Tolerance
The amount of magnesium found on the working curve is more;
The sample amount.
m,
nV
X100% ·
The analytical value between laboratories should be greater than the tolerance listed in Table 5. When using a standard sample for calibration, it shall not exceed 1/2 of the tolerance listed in Table 5 Table 5
Magnesium content
1.00~2.00
>2.00~5.00
Public
Difference
0.20
%
359
6 Tolerance
The amount of magnesium found on the working curve is more;
The sample amount.
m,
nV
X100% ·
The analytical value between laboratories should be greater than the tolerance listed in Table 5. When using a standard sample for calibration, it shall not exceed 1/2 of the tolerance listed in Table 5 Table 5
Magnesium content
1.00~2.00
>2.00~5.00
Public
Difference
0.20
%
359
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