This standard specifies the method for determining the amount of aluminum in aluminum alloys by sodium hydroxide separation-chelate titration. This standard is applicable to the determination of the amount of acid-soluble aluminum in iron-chromium-aluminum alloys. Determination range: 3% to 8.00%. JB/T 9548.8-1999 Chemical analysis method for iron-chromium-aluminum alloys Determination of aluminum content by sodium hydroxide separation-chelate titration JB/T9548.8-1999 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Chemical analysis methods of iron-chromium-aluminium alloys
Sodium hydroxide separation-chelate titration method for the determination of aluminium content1Scope
This standard specifies the method for determining the aluminium content in iron-chromium-aluminium alloys by sodium hydroxide separation-chelate titration method. This standard is applicable to the determination of acid-soluble aluminium content in iron-chromium-aluminium alloys. Determination range: 3.00%~8.00% 2 Method Summary
JB/T9548.8-1999
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After the sample is dissolved with acid, add excess EDTA to the filtrate separated by sodium hydroxide. At pH 5.5, use PAN as an indicator, use copper standard solution to back-titrate the excess EDTA, add ammonium fluoride to release the EDTA integrated with aluminum, and then titrate with copper standard solution. 3 Reagents
3.1 Sodium hydroxide.
3.2 Hydrochloric acid-nitric acid mixed acid: hydrochloric acid (density p1.19g/ml) + nitric acid (density p1.42g/ml) + water (1+1+1). 3.3 Ammonium hydroxide (1+1)
3.4 ​​Hydrochloric acid (1+1).
3.5 Disodium ethylenediaminetetraacetate (EDTA) solution: 0.02000mol/L Weigh 7.4448g EDTA, put it in a beaker, dissolve it with water, transfer it to a 1000ml volumetric flask, dilute it to the mark with water, and mix it. Store it in a plastic bottle. 3.6 Acetic acid-sodium acetate buffer solution (pH5.5): Weigh 123g sodium acetate (NaAC·3H,0) and dissolve it in 800ml water, add 6ml glacial acetic acid (density g1.05g/ml) and dilute it to 1000ml with water, and mix it. 3.7 Ammonium fluoride solution: (20g/L).
3.8 Copper standard solution: (0.01mol/L), 3.8.1 Preparation: Weigh 0.6355g electrolytic copper (99.9% or more) and place it in a 125ml conical beaker, cover with surface III, dissolve with a small amount of nitric acid (1+1) and evaporate to dryness, add water to dissolve salts, adjust to pH 5 with ammonium hydroxide (3.3) and hydrochloric acid (3.4), transfer to a 1000ml volumetric flask, dilute with water to the mark, and mix. 3.8.2 Calibration: Weigh 0.2000g pure aluminum (purity greater than 99.9%) and place it in a 250ml plastic beaker, add 2g sodium hydroxide (3.1) and 5ml water, heat in a water bath to dissolve, acidify with hydrochloric acid (3.4) and add 5ml excess, cool, transfer to a 200ml volumetric flask, dilute with water to the mark, and mix. Pipette 20.00 ml aluminum solution (equivalent to 20 mg aluminum) into a 250 ml conical beaker, add 0.350 g reduced iron powder, and proceed as in 4.2.1 to 4.2.2.
Calculate the mass of aluminum equivalent to each ml copper standard solution according to formula (1), g/ml. Approved by the State Bureau of Machinery Industry on August 6, 1999 56
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Where: m-
-The mass of pure aluminum transferred, g;
JB/T 9548.8-1999
V,—The volume of the filtrate transferred after precipitation, ml;V—The total volume of the precipitate, ml;
Vz—The volume of the copper standard solution consumed in the second titration, ml. (1)
3.9 Bromocresol green indicator solution (1 g/L): Weigh 0.1 g of the reagent and place it in a 100 ml beaker, then add 0.1 g of sodium hydroxide (3.1) and 100 ml of water, and stir to dissolve.
3.101 (2-pyridyl azo)-2-naphthol (PAN) indicator solution (1 g/L): Dissolve 0.1 g of the reagent in 100 ml of ethanol. 4 Analysis steps
4.1 Test materials
Weigh the test materials according to Table 1, accurate to 0.0001 g. Table 1
Aluminum content%
3.00~5.50
>5.50~8.00
4.2 Determination
Weigh the sample mass
4.2.1 Place the sample in a 250ml conical beaker, add 15ml mixed acid (3.2), heat to dissolve and evaporate to near dryness, add 100ml water and heat to near boiling, remove, add 6g solid sodium hydroxide (3.1) in portions, after the violent reaction stops, shake the beaker thoroughly, cool to ambient temperature, transfer to a 250.ml volumetric flask, and use Dilute with water to the mark, mix well, dry filter, transfer 50.00 ml of the filtrate into a 250 ml conical beaker, pre-add 12.0 ml of EDTA solution (3.5), add a drop of bromocresol green indicator solution (3.9), neutralize with hydrochloric acid (3.4) until the solution changes from yellow to yellow, then add ammonium hydroxide (3.3) until it turns blue, add 15 ml of acetic acid-sodium acetate solution (3.6), boil for 2 min, add 4-5 drops of PAN indicator solution (3.10), and titrate with a pot of standard solution (3.8) until the solution turns light purple (ignore the reading). 4.2.2 Add 10 ml of ammonium fluoride solution (3.7), boil for 1-2 min, add 5-6 drops of PAN indicator solution (3.10), and continue to titrate with copper standard solution (3.8) until the solution changes from yellow-green to blue-purple as the end point: 5 Calculation of analysis results
Calculate the percentage of aluminum according to formula (2):
AI (%) =+
Wherein: C-
The mass of aluminum equivalent to each milliliter of copper standard solution, g/ml; The total volume of sample solution precipitation, ml;
-The volume of standard solution consumed in the second titration of the sample solution, ml; V
Vs-The volume of the filtrate removed after precipitation, ml; m
6 Allowable difference
The mass of the sample, g.
The difference in analytical results between laboratories should not be greater than the allowable difference listed in Table 2, (2)
3.00~5.50
>5.50~8.00
JB/T 9548.8-1999
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