Some standard content:
JB/T7995-1999
This standard is a refinement of JB/T7995-95 (GB9257-88) Chemical Analysis Method for Black Jade. The technical content of this standard is consistent with JB/T7995-95, and it has only been re-edited according to relevant regulations. This standard replaces JB/T7995-95 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 is Zhengzhou Abrasives and Grinding Tools Research Institute. The main authors of this standard are Kang Jichang and Cheng Ruida. 212
Machinery Industry Standard of the People's Republic of China
Black corundum
Chemical analysis method
JB/T 7995·1999
Replacement #JB/T 7985-95
This standard specifies the determination method of silicon dihydride, titanium dioxide, total iron, aluminum oxide, calcium complex, and chemical composition in black corundum. This standard is applicable to the determination of the chemical composition of industrial first-stage black jade products. Referenced standards
The provisions contained in the following standards constitute the provisions of this standard by citing them in this standard. The versions indicated are valid at the time of publication of this standard. All standards are subject to revision. Parties using this standard should explore the possibility of using the following standards in linked versions. Sampling method for ordinary abrasives
GB/T 4676·1984
General provisions
3.1 During the extension load analysis, the number of parallel copies of the same sample shall not be less than three. The difference in the analysis results shall be within the allowable cut-off value. The arithmetic mean shall be taken as the final analysis result.
3.2 Unless otherwise specified, the reagents used in the analysis shall be of analytical grade not less than analytical grade. The reference reagent shall be used as the benchmark. The water used for analysis shall be waste water or deionized water unless otherwise specified. 3.3 Liquid reagents with concentrations specified in the methods refer to concentrated liquids. The percentage of liquid is the percentage of liquid by weight/volume, which refers to the number of grams of liquid contained in 100 mL of liquid. (1+1), (1+2), etc., refers to the ratio of the liquid volume to the water volume. 3.4
Analytical balances should be calibrated regularly if the required volume reaches 0.1 mg/mL. 3.5 Burettes, volumetric tubes, pipettes and other measuring instruments should be calibrated. 3.6 All operations in the method are performed in a single instrument unless otherwise specified. 3.7 The "burn to constant weight" in the method means that after two consecutive burns and cooling in a centrifuge, the difference between the two weighings does not exceed 0.2 mg.
In each determination, a blank test should be performed at the same time to correct the analysis results. 3.8
3.9 Sample sampling shall comply with the provisions of GB/T4676. The analytical sample shall pass through a 100μm sieve. Before analysis, place it in a dryer at 105~110℃ for 2 hours and cool to room temperature. 3.10
Determination of silicon dihydride by gravimetric molybdenum blue photometry. The determination range of this method is: 5.00% or more. 4.1 Method specifications
The sample is decomposed by melting with a sodium carbonate-abrasive mixed flux, and then precipitated with salt gel and then precipitated to a precipitate state. A gelling agent is added to precipitate silicic acid, which is then precipitated and burned into silicon dioxide. It is then treated with hydrochloric acid to volatilize and remove the silicon in the form of canalized silicon. The weight difference before and after the hydrochloric acid treatment is the silicon dioxide in the precipitate. Quantity, use the spectrophotometric method to determine the amount of silicon dioxide in the liquid or residual silicon dioxide, the sum of the two is the content of silicon dioxide in the sample.
4.2 Reagents
4.2.1 Mixed flux: Mix one part of anhydrous sodium carbonate with two parts of sand making standard spoon. Figure National Machinery Industry Bureau 1999-05-20 approved 2000-01-01 field
Salt load (density 1.19),
Salt section (5+95), (1+2)
Animal tape pack (2%).
Hydrochloric acid (40%,
Sulfuric acid (1+1),
Potassium thiocyanate solution (5%).
Citric acid enzyme solution (1),
Acid solution (5%),
JB/T 79951999
Silicon dioxide mixed acid (1 + 1): Measure one part of 5% oxalic acid and mix it with one part of sulfuric acid (1 + 3) to prepare ammonium ferric sulfate dense solution (6%).
Silicon dioxide standard sea solution
Weigh 0.1000g of silicon dioxide (99.99%) after calcination at 1000C for 1h in sodium hydroxide, add 2g of anhydrous sodium carbonate, mix with silk and then add 0.5g, melt in a high-temperature furnace at 860~900C for 20min, remove from the heat, cool, wash the outer wall, put it in a plastic cup, pour boiling water over it and cool to room temperature, transfer it to a 1000mL volumetric flask, dilute it to the scale with water, mix well, and immediately transfer it to a dry plastic bottle for storage. This part contains 0.1mg silicon dioxide, divide 50.00mL of the above solution into 10ml , put 2.5N acetic acid in a 250mL volumetric bottle, dilute to the concentration with water, mix well, this solution is the standard solution containing 0.02mg of silicon dioxide per liter, 4.3 instrument
spectrophotometer.
working standard drawing
take 0.00, 0.50, 1.00.2.00, 3.00.4.00, 5.00, 6.00ml. silicon dioxide standard solution is placed in a group of 100ml. volumetric flasks, add 12ml of 5+95 acid, adjust to 35ml with water, add 5ml of group A (5%).. after 2min, add 20mL of thiosulfate (1+1>, use 2cm colorimetric precision at 700nm wavelength on the spectrophotometer, measure its absorbance with the sample blank as reference, and make working monitoring line.
4.5 Analysis method
Weigh 0.5000g of the sample (blank test with the sample) in a platinum field, add 3g of mixed flux. Stir with platinum wire and cover to melt 1g. Cover and place in a high-temperature furnace, melt at 1000~1080℃ for 1h. Take out. Rotate to make the molten material adhere to the inner wall of the furnace, cool, wash the glass, place in a 250mL dye cup, add 60ml of hydrochloric acid (1+2), soak the molten material, filter out the residue, heat the solution at low humidity until it is in the form of a salt, add 10ml of hydrochloric acid, gelatin (2%>5ml L. Stir for 1 minute, keep warm in 70℃ water solution for 15 minutes. Heat hydrochloric acid (5+95%) to make the dissolvable salts just dissolve, filter with medium-speed quantitative filter paper, collect the filtrate in a 250mL volumetric flask, first wash the precipitate with hot acid (5+95%) until there is no iron ion (check with potassium thiocyanate solution), and continue to wash with warm water until there is no chloride ion (check with nitric acid solution). Transfer the precipitate with the hot paper into a platinum agar, carefully dry the medium, and then put it into a high-temperature furnace after incineration at 100℃ for 1b, take it out and place it in a desiccator to cool to room temperature, melt, and repeat the incineration until the precipitate is completely dissolved. Constant weight, add 3-5 drops of water to the inner wall of the snail to moisten the precipitate, add 4 drops of vegetable melt (1), 5 mL of hydrochloric acid. Evaporate at low temperature until white smoke appears, remove, cool slightly, and then add 5 mL of hydrochloric acid. Continue evaporating until the smoke is gone, expose the residual flow together with the ground in a 1000C high-temperature furnace for 15 minutes, take out and place in a desiccator to cool to room temperature, weigh, and repeatedly burn to constant weight. Dilute the bond wave after separating the silicate with water to the scale, take 10.00 mL and cut it into a 100 mL volumetric flask, add 25 mL of water, 5 ml of ammonium sulfate solution (5%), and let it stand for 20 minutes (When the liquid temperature is lower than 15°C, heat it to above 15°C. When it is higher than 25°C, let it stand for 10 minutes.) Add 20mL of mixed acid 1+1) and 5mL of slightly acidic sub-fast recovery liquid (6%). Dilute it with water to the desired concentration, add water and let it stand for 30 minutes. Use a 2rm ratio spectrophotometer to measure the absorbance at 700nm and take the blank sample as reference. Calculate the percentage of silicon dioxide using formula (1): m: × 100% +
w(Sio,)
×100%
JB/T 7995—1999
Mass of anti-precipitate and platinum before hydrochloric acid treatment, 8: Where,,---
Mass of anti-precipitate and platinum after hydrochloric acid treatment, %.
The amount of silicon dioxide found on the working curve-g:,
V--Total volume of test solution, mL:
Volume of test solution, mL:
Weight of sample·g
Allowable difference
The difference between the analysis results of laboratories should not be greater than the allowable difference listed in Table 1, and the allowable difference within the laboratory should be less than the debt shown in Table 1. Table 1
Silicon dioxide content
5. 00~15. 00
Determination of silicon dioxide by Hu blue photometry
The determination range of this method is: less than 5.00%. 5.1
Method Summary
Allowable Difference
After sample decomposition, within 0.1~0.Add the corresponding acid to the 15N test acid medium to dissociate the silicic acid to form silicic acid heteropolyacid, reduce it to silicic acid with ascorbic acid, and measure its absorbance at a wavelength of 680nm on a spectrophotometer. 5.2 Reagents
Mixed flux, grind one part of anhydrous sodium carbonate and two parts of slag, 5.2.1
Hydrochloric acid (10+90),
5.2.3 Anhydrous ethanol.
5.2.4 Acid ammonium sulfate solution (5%).
5.2.5 Hydrochloric acid (1+1).
5.2.6 Anti-cyclohexane acid solution (1%),
Silicon dioxide standard solution
Weigh 0.1000g of silicon dioxide (99.99X>) calcined at 1000°C for 1 h in a platinum tongs, add 2g of anhydrous sodium carbonate, carefully hook with platinum wire and then cover with 0.5g. Melt at 860~900°C for 20min, take out, cool, wash the outer wall, and place in a The solution contains 0.1 mg silicon dioxide per liter. Take 100 mL of the upper solution and put it into a 200 mL volumetric flask filled with 10 mL hydrochloric acid (2N), dilute it to the mark with water, shake it, and the solution contains 0.05 mg of sodium dioxide standard solution. Sodium dichloride (99.99%).
Anhydrous sodium carbonate (primary reagent),
5.2.10 Blank solution
Weigh 2g of mixed flux and place it in a platinum tube, melt it at 980C for 20min, take it out, cool it down, wash the outside of the tube, heat it with acid (10+9080ml.. to condense, cool it down and transfer it to a 260ml. volumetric flask, dilute it with water to the temperature, and shake it. 5.3 Instrument || tt||Spectrophotometer.
Working line of the sample
Take 11 portions of the sample and reduce the volume by 20ml, and place them in a group of 100mL volumetric bottles. Add 0.00, 0.80, 1.60, 2.40, 3.20, 4,00, 4.80, 5.60, 6.40, 7.20, 8.00ml of silica standard drop rate in sequence. Adjust the volume to 40ml with water. Add 215% anhydrous ethanol
JB/T 79951999
10mL, 5ml of 5% acid solution, mix well, let stand for 20min, add 1+1>30mL of acid, mix well, let stand for 3min, add ascorbic acid solution (1%>5ml.. Dilute to 100mL with water, mix well, let stand for 1h, use 1cm colorimetric precision at 680nm on the spectrophotometer, measure its absorbance with blank as reference, draw the working curve, 5.5 Analysis method
Weigh 0.1000g of sample in platinum tongs, add 1.5g of mixed flux. Stir well with platinum wire gauge and cover with 0.5g of flux, put in a high temperature furnace, and heat at 1000~ Melt at 1080℃ for 40min, take out, transfer to a flask to make the molten sample adhere to the inner wall of the glass, cool, wash the outer wall of the sample, place in a 250mL cup, add boiling 10+9080mL of 4% ethanol, heat and diffuse, remove the sample and the solution, cool and transfer to a 250mL volumetric flask, dilute to the mark with water, and add 20mL of the sample to the flask.
Take 20mL of the above sample and place in a 100mL volumetric flask, add 20mL of water and 10mL of anhydrous ethanol, and perform the following analysis steps according to the working curve. Measure the light intensity with the blank sample as the ratio. Calculate the percentage of silicon dioxide according to formula (2): x100%
w(SiO2,) =
Where: m,--Silicon dioxide content obtained from the working solution·gV-..Total volume of test solution.mL
V,-Test solution volume,mL
Allowable difference
Sample mass·g.
+.++-( 2 )
The difference in analysis results between laboratories should not be greater than the allowable difference shown in Table 2, and the allowable difference within the laboratory should be less than the value shown in Table 2. Table 2
Silicon dioxide content
0. 50~5. 00
Determination of titanium dioxide by hydrogen peroxide optical density method
The determination range of this method is: 0.50~6.00%, 6.1
Method Summary
Supplementary allowance
In an acidic medium of 1.2~3.5N, the tetravalent solution reacts with hydrogen peroxide to form a yellow complex, and the absorbance of the color solution is measured at a wavelength of 420~430nm.
The yellow solid state of trivalent iron ions is determined, and the interference is eliminated by using the sample room white (without hydrogen peroxide) as a reference when determining the aurora of the complex. In order to make all the divalent iron in the solution in the trivalent form, a small amount of sulfur is added to dissolve the oxidant. 6.2 Trial production
6.2.1 Coagulation flux: One part of sodium ferric sulfate and two parts of acetone sand are finely ground and mixed. 6.2.2
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Put 250mL of water in a 400mL beaker, cool and transfer to a 500mL volumetric flask. Wash the two porcelain cups. Wash them fully and combine them in a 5/0mL volumetric flask. Dilute with water to the scale. This solution contains 1mg titanium dioxide per liter. Take 50mL of the above titanium dioxide standard solution and put it into another 500mL volumetric flask. Add water to the scale. According to the average, this solution is the titanium dioxide standard solution containing 0.1mg per milliliter. Use 6.3
spectrophotometer.
Drawing of working curve
Take seven portions of titanium dioxide standard with 0.00, 5.00, 10.00, 15.00, 20.00, 25.00, 30.00mL and place them in a 100ml volumetric flask, add 20mL of 1+3 acid, 5mL of hydrogen peroxide (5%), dilute with water to the concentration, and use 2cm colorimetric II at 430nm wavelength on the spectrophotometer, and measure the limit light with the reagent room's self-made ratio to draw the working curve. 6.5 Analysis method
Weigh 30ml of 0.5000g bullet (accompanying blank test). Mix well with platinum zirconium, add 3g of mixed flux, mix carefully, and then cover with 1g of mixed flux. Send into a high-temperature furnace. Melt at 1000-1080C for 1h, take it out, and rotate it so that the molten material adheres to the smoky inner chamber. After cooling, wash the outer seat, put it into a 250ml beaker containing 100mL of near-boiling acid <5+95>, heat it on sand to leach it out, wash the crucible and the whole with water, transfer it to a 250mL volumetric flask, cool it, and dilute it to the scale with water. Take two portions of 25 mL of the above solution and place them in two 100 mL measuring tubes respectively, add 20 mL of sulfuric acid (1+3) to one of them, add 5 mL of sodium nitrite (3%) in a stirring medium, dilute to the scale with water, add 20 mL of sulfuric acid (1+3) and 5 mL of hydrogen peroxide solution (3%) to the other solution, dilute to the scale with water, mix well, use 2 nm colorimeter and measure the absorbance at a wavelength of 430 nm on a spectrophotometer with the above-mentioned sodium nitrite solution as a reference. Calculate the percentage of titanium dioxide according to formula (3): w(TiO2) =
Wherein: ,——dichlorodioxide deficiency obtained from the working curve, g; V--total volume of solution, ml;
V-volume of dissolved wave, mL;
Sample mass·K
6.6Tolerance
X1005%
The difference between the analysis results of laboratories should not be greater than the allowable difference listed in Table 3. The allowable difference in the laboratory should also be less than the value calculated in Table 3. Table 3
Class II drinking volume
0. 50~3. 00
>3, 00~6. 00
Determination of total iron (expressed as Fe,O,) by sulfosalicylic acid limit spectrophotometry. The determination range of this method is: 1.00%~5.00%, 7.1 Method Summary
Bei Xu Fan
+( 3 )
In ammonia medium, trivalent iron and chloridosalicylic acid form a yellow complex, and the absorbance of the most colored solution is measured at a wavelength of 430m. 7.2 Reagents
Borate-sodium argentate mixed reagent (2+1), weigh two parts of borax and one part of anhydrous sodium carbonate and mix them, 7.2.1
7.2.2 Hydrochloric acid (15+85)
Hydrochloric acid (1+1).
7.2.4 Hydrogenated water (1+t).
7.2.5 Sulfonic acid (20%),
7.2.6 Ferrous oxide standard
JB/T 7995—1999
0.5000g of ferric oxide (standard reagent) calcinated at 600°C for about 30min in a 200mL beaker, add a few drops of water and then add 40mL of hydrochloric acid (1+1). Cover the surface and heat at low temperature to dissolve, remove, cool to room temperature, transfer to a 500ml volumetric flask, dilute to the mark with water, and the solution contains 1.0 ferric chloride. Take 50mL of the above solution and put it in a 500ml volumetric flask, dilute to the mark with a glass, and hook it. This solution is the standard enzyme solution containing 0.1 mg of ferric oxide per liter.
7.3 Working curve
Take nine portions of the standard solution of ferric oxide, 0, 00, 0.50, 1.00, 2.00, 3.00, 4.00, 5.00, 6.00, 7.00 mL, and place them in a 100 mL volumetric flask. Add 10 ml of hydroxysalicylic acid (20>6), and add nitrogen water (1+1) while shaking until the solution turns a yellow color, and add 2 mL in excess. Dilute to the scale with water. , shake well, measure the absorbance at 430nm wavelength on the spectrophotometer with a 1cm colorimetric straight tube and use the test blank as a reference, draw a working curve,
7.4 Preparation of test solution
Accurately weigh 0.5g of the sample and put it into 3g of platinum additive that has been mixed with a melt, stir evenly and then cover it with 1g of degassing agent, add, put it in a high humidity furnace mouth (furnace door half open) for 10min and then shrink it at 980~1100℃. Melt for about 1 hour, take out the sample after it is shelled, rotate the mold to make the molten material adhere to the mold, wash the outside of the mold with water, put it in a 250mL beaker containing 100ml of the gasket (15+85), heat and extract, wash the mold with water, transfer the residual liquid to a 250mL volumetric flask, cool to ambient temperature, dilute to the scale with water, hook, set aside, and use it as a blank with the sample. 7.5 Analysis method
Take 5.00 10.00ml test solution (see 7.4) is placed in a 100ml volumetric bottle, 10ml of sulfonic acid citric acid solution (20%) is added, and ammonia water (1 + 1) is added dropwise until the liquid turns a certain yellow color, and 2ml of excess is added. Dilute to the scale with a water dispenser, and place the pointer on the spectrophotometer at 430mm in length with a 1cm colorimetric block. Measure its absorbance with the blank of the sample as a reference, and calculate the percentage of magnesium trioxide according to formula (4): w(Fe,O,) =
Wherein, m-
the amount of ferric chloride obtained from the working curve, 8total volume of test solution, mL;
V,-—volume of test solution taken, ml.:
use-—amount of standard sample, g.
7.6Tolerance
The difference between the analysis results of laboratories should not be greater than the allowable difference listed in Table 4, and the allowable difference within the laboratory should be less than the value stated in Table 4. Table 4
Dioxide
0. 50~2. 00
>2. 00~5. 00
8Potassium dichromate volumetric legal total iron (expressed in the form of Fe,O,) The standard diagram of this type of coupon is: 5.00% or more. 8.1Method Summary
Allowed delivery
.( 4 )
In a normal acid medium, use stannous chloride to reduce trivalent ions to generate divalent ions, then use dichloromethane to aminate excess stannous oxide, use sodium diphenylsulfonate as an indicator, and use potassium dihydrogen sulfate standard solution to titrate the divalent iron. 8.2 Reagents
8.2.1 Acid pad (density 1.15).
Acid test (1+1).
Sodium hydroxide (20>6),
Acid (density 1.84).
Phosphoric acid (density 1.70)
Slightly mixed acid-weak acid solution: under low temperature, slowly add 150mL of acid (density 1.84) to 700mL of water, cool and then add 150mL of phosphoric acid (density 1.70),
Dichlorobenzene solution (10X): heat 10g of tin dioxide and add it to 20mL of tin oxide (density 1.19). Dilute to 100mL with water and stir.
Prepare saturated solution (about 5%); weigh 5g of dichlorobenzene and add it to 100mL of hot water, cool and take the upper layer of liquid for use. 8.2.9
Diphenylsulfonic acid yellow solution (0.5%). Potassium dichromate standard solution (0.0100N):
Weigh 0.4904g of potassium dichromate (standard reagent) dried at 150°C for 2h and equal to 1(K)mL of water, transfer to a 1000mL volumetric flask, dilute to scale with water, and mix well.
8.3 Analysis method
Take 50mL of the test solution (see 7.4) in a 250mL beaker, add sodium hydroxide solution (20%) to produce a large amount of white precipitate and dissolve it, and add 10mL in excess and heat to near boiling, stir and keep moist for 10min, after the precipitate disappears, filter it with medium-speed filter paper, and remove the precipitate on the funnel with 40mL of hot hydrochloric acid (1+1) and dissolve it in the original standard, wash it with hot water 8~10 times, evaporate the solution to about 20ml, add hot oxycarbon to dissolve until the yellow color disappears, then add 1~2 drops in excess, and cool to room temperature with running water. Rapidly add 20mL of saturated oxidizing solution. At this time, a self-colored filamentous mercurous chloride precipitate appears in the solution. Let it stand for 3-5 minutes, add 50mL of water, 10mL of mercapto mixed acid and 2-3 drops of sodium diphenylamine sulfonate as an indicator, and immediately titrate with potassium dichromate standard solution until a solid color appears. If it does not fade for 30 minutes, it is the end point. Calculate the percentage of ferric oxide by sieve according to the formula (S): 0.079.8SVN×100%
te(Fe,O,)-9
Wherein; V-volume of potassium dichromate standard solution consumed at regular intervals, mL; N
0.079 85-
equivalent concentration of potassium dichromate standard solution: milligram equivalent of ferric oxide:
sample weight·g
total volume of test solution, mL:
volume of test solution taken, ml.
8.4 Allowable Difference
The difference between the analysis results of the laboratory shall not be greater than the allowable difference listed in Table 5, and the indoor allowable difference shall be less than the value shown in Table 5. Table 5
Iron trioxide
>5, 00~10. 00
>10, 00~20, 00
>20, 00~ 30. 00
Allowable Difference
EDTA quantitative method for determination of aluminum oxide
The determination range of this method is: 40%~80%.
9.1 Summary of the method
JB/T 79951999
In an acid solution, trivalent lead ions react with EDTA to form a medium-strength complex. This reaction is slow and cannot be used directly for titration. Back titration is required, that is, first add an excess of EDTA standard solution, adjust the pH to about 2.3, heat to make the trivalent aluminum ions and EDTA complex completely, and then adjust the pH to 5-6. Using xylenol as an indicator, use zinc salt standard solution to clear the excess EDTA until the liquid changes from yellow to orange-red as the end point. The aluminum content is obtained based on the volume (mL) of the EDTA standard actually consumed. Iron and zinc content are determined in a hydrochloric acid solution of not less than 10%. The copper iron reagent is used to react with iron, titanium, etc. or precipitate and then precipitate in trichloromethane to separate and remove.
9.2 Trial production
9.2.1 Hydrogen water (1+1).
Hydrochloric acid (1+1).
Iron reagent solution (6%): Prepare before use. Use after filtering, methyl orange indicator (0.05%).
Hexamethylenetetramine solution (15%).
Xylenol indicator (0.5%),
Triazine.
9.2.8 EDTA standard solution: 0.05M.
Weigh 18.61g of EDTA in a 400ml beaker, add 200mL of water. Heat at low temperature to dissolve, cool and quickly pour into a 1000ml volumetric flask, dilute to the scale with water, and add a hook. b) Calibration:
Accurately take 1.7848g of calcium sulfate (standard reagent) dried at 110°C for 2h in a 250mL beaker, add 50mL of water, and dropwise add 1+1 until completely dissolved. Add excess 2~3 times of water and heat to remove the dioxide. After cooling, transfer to 1000ml.In a volumetric flask, dilute to the mark with water and mix well. This solution is the standard solution containing 1 mg of calcium oxide per liter. Take 50 mL of the above instant solution and put it in a 300 mL flask. Add 100 mL of water and 10 mL of sodium hydroxide (20%). Mix well and add a small amount of reagent acid sodium salt indicator. Titrate with the prepared EDTA standard solution until the pure color is the end point. Under the same conditions, perform a micro-blank test. Calculate the titer of the EDTA standard solution to calcium oxide according to formula (6): Too = Www.bzxZ.net
In the formula, m
is the weight of calcium oxide, g:
is the volume of the EDTA standard solution consumed during titration (the blank value has been subtracted>, mL.): V
Top = - The titer of the EDTA standard solution to calcium oxide, g/mL. 9.2.9 Sulfur-containing zinc standard solution 0.026 M.
a) Weigh 7.2 g of sulfuric acid and add it to 250 ml of calcined water. In the ring, add 100mL of water and stir to dissolve, add carboxylic acid (100mL) dropwise to make it clear, transfer to a 1000mL volumetric flask, dilute to the mark with water, mix well and set aside. b) Calibration:
Accurately collect 10mL of 0.05M EDTA standard solution in a 250mL flask, add 50mL of water, 5mL of hexamethylenetetramine solution (15mL), and 1 drop of xylenol indicator, and use the prepared carboxylic acid standard solution to stabilize until the color changes from yellow to slightly red.
Calculate the volume of 1mL of EDTA standard solution relative to carboxylic acid standard solution according to formula (7): -
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