GB/T 223.8-2025 PDF English
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GB/T 223.8: Historical versions
| Standard ID | USD | BUY PDF | Delivery | Standard Title (Description) | Status |
| GB/T 223.8-2025 | 320 | Add to Cart | Auto, 9 seconds. | Iron, steel and alloy - Determination of aluminium content - Titrimetric method and spectrophotometric method | Valid |
| GB/T 223.8-2000 | 249 | Add to Cart | 3 days | Methods for chemical analysis of iron, steel and alloy. The sodium fluoride separation. EDTA titration method for the determination of aluminium content | |
| GB/T 223.8-1991 | RFQ | ASK | 3 days | Methods for chemical analysis of iron, steel and alloy--The sodium fluoride separation-EDTA volumetric method for the determination of aluminium content | Obsolete |
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GB/T 223.8-2025: Iron, steel and alloy - Determination of aluminium content - Titrimetric method and spectrophotometric method
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GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 77.080.01 CCS H 11 Replacing GB/T 223.8-2000, GB/T 223.9-2008 Iron, Steel and Alloy - Determination of Aluminum Content - Titrimetric Method and Spectrophotometric Method Issued on: AUGUST 29, 2025 Implemented on: MARCH 1, 2026 Issued by. State Administration for Market Regulation; Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword... 3 1 Scope... 5 2 Normative References... 5 3 Terms and Definitions... 6 4 Method 1.Sodium Fluoride Separation-EDTA Titration Method... 6 5 Method 2.Chrome Azurol S Direct Spectrophotometry... 10 6 Method 3.Copper-iron Reagent Separation - Chrome Azurol S Spectrophotometry ... 15 7 Test Report... 20 Appendix A (informative) Constituent Documents of GB/T 223... 21 Appendix B (informative) Additional Data from Joint Precision Tests... 26 Appendix C (informative) Additional Data from Joint Precision Tests... 27 Appendix D (informative) Additional Data from Joint Precision Tests... 28 Iron, Steel and Alloy - Determination of Aluminum Content - Titrimetric Method and Spectrophotometric Method WARNING. personnel using this document shall have practical experience working in a formal laboratory. This document does not address all potential safety issues. Users are responsible for taking appropriate safety and health precautions and ensuring compliance with relevant national regulations.1 Scope
This document describes the methods for determining the aluminum content in iron, steel and alloy. sodium fluoride separation-EDTA titration, chrome azurol S direct spectrophotometry, and copper-iron reagent separation-chrome azurol S spectrophotometry. Method 1, sodium fluoride separation-EDTA titration, is suitable for determining the aluminum content in iron, steel and alloy with a mass fraction of 0.50% ~ 10.00%. Method 2, chrome azurol S direct spectrophotometry, is suitable for determining the acid-soluble aluminum content in iron, steel and alloy with a mass fraction of 0.050% ~ 1.00%. Method 3, copper-iron reagent separation-chrome azurol S spectrophotometry, is suitable for determining the aluminum content in iron, steel and alloy with a mass fraction of 0.015% ~ 0.50%.2 Normative References
The contents of the following documents constitute indispensable clauses of this document through the normative references in the text. In terms of references with a specified date, only versions with a specified date are applicable to this document. In terms of references without a specified date, the latest version (including all the modifications) is applicable to this document. GB/T 6379.1 Accuracy (trueness and precision) of Measurement Methods and Results - Part 1. General Principles and Definitions GB/T 6379.2 Accuracy (trueness and precision) of Measurement Methods and Results - Part 2. Basic Method for the Determination of Repeatability and Reproducibility of a Standard Measurement Method GB/T 6682 Water for Analytical Laboratory Use - Specification and Test Methods GB/T 7729 Chemical Analysis of Metallurgical Products - General Rule for Spectrophotometric Methods GB/T 12805 Laboratory Glassware - Burettes GB/T 12806 Laboratory Glassware - One-mark Volumetric Flasks GB/T 12808 Laboratory Glassware - One Mark Pipettes GB/T 20066 Steel and Iron - Sampling and Preparation of Samples for the Determination of Chemical Composition3 Terms and Definitions
This document does not have terms or definitions that need to be defined.4 Method 1.Sodium Fluoride Separation-EDTA Titration
Method 4.1 Principle Dissolve the test portion in acid. Use ammonium citrate and ammonium oxalate to complex iron, chromium, nickel and manganese, etc. In a solution with pH 4 ~ 5, use sodium fluoride to separate the aluminum precipitate from the coexisting elements. The precipitate is dissolved with a mixed acid of hydrochloric acid-boric acid. After the filter paper is damaged and fluoride is removed with nitric acid and perchloric acid, add excess EDTA solution to a slightly acidic solution. At approximately pH 6, use xylenol orange as an indicator. Use zinc standard solution to titrate the excess EDTA solution. After complexing fluoride ions with aluminum, release EDTA, which is then titrated again with zinc standard solution. When the total content of zirconium, cerium and rare earth elements in the solution does not exceed 50 mg, it does not interfere with the determination of aluminum. 4.2 Reagents and Materials Unless otherwise specified, only reagents confirmed to be of analytical grade and Grade II water as specified in GB/T 6682 or water of equivalent purity are used in the analysis. 4.2.1 Sodium pyrosulfate (potassium). 4.2.2 Sodium fluoride. 4.2.3 Hydrochloric acid. ρ is approximately 1.19 g/mL. 4.2.4 Hydrochloric acid (1 + 1). Dilute with hydrochloric acid (4.2.3). 4.2.5 Nitric acid. ρ is approximately 1.42 g/mL. 4.2.6 Perchloric acid. ρ is approximately 1.67 g/mL. 4.2.7 Sulfuric acid. ρ is approximately 1.84 g/mL. 4.2.8 Sulfuric acid (1 + 1). Dilute with sulfuric acid (4.2.7). 4.2.9 Sulfuric acid (2 + 100). Dilute with sulfuric acid (4.2.7). 4.2.10 Hydrofluoric acid. ρ is approximately 1.15 g/mL. 4.2.11 Ammonia solution. ρ is approximately 0.90 g/mL. 4.2.12 Ammonia solution (1 + 1). Dilute with ammonia solution (4.2.11). 4.2.13 Sodium fluoride solution (35 g/L). Store in a plastic bottle. 4.2.14 Sodium fluoride solution (5 g/L). Store in a plastic bottle. 4.2.15 Complexing agent solution. mix ammonium citrate solution (400 g/L) and ammonium oxalate solution (50 g/L) in equal volumes. 4.2.16 Hydrochloric acid-boric acid mixed acid. mix saturated boric acid solution, hydrochloric acid (4.2.3), and water in a ratio of (15 + 25 + 60). 4.2.17 Acetic acid-ammonium acetate buffer solution (pH 5.0 ~ 5.5). weigh-take 200 g of ammonium acetate and dissolve it in 500 mL of water. Add 25 mL of glacial acetic acid (ρ is approximately 1.05 g/mL) and use water to dilute it to 1 L. Mix well. 4.2.18 2,4-dinitrophenol solution (2 g/L). weigh-take 0.2 g of 2,4-dinitrophenol ammonium acetate, dissolve it in approximately 50 mL of ethanol (1 + 1) (1 portion of ethanol + 1 portion of water), add ethanol (1 + 1) to a final volume of 100 mL, and mix well. 4.2.19 Xylenol orange solution (2 g/L). prepare fresh in summer; in winter, do not exceed one week after preparation. 4.2.20 Ethylenediaminetetraacetic acid disodium salt (EDTA) solution (0.02 mol/L). weigh- take 7.4448 g of EDTA, place it in a 400 mL beaker, dissolve it in water, transfer it to a 1,000 mL volumetric flask, dilute to the scale, and mix well. 4.2.21 Zinc standard solution (cZnO = 0.0200 mol/L). weigh-take 1.6276 g of zinc oxide (primary standard) that has been dried to constant mass at 110 C, place it in a 400 mL beaker; add 20 mL of hydrochloric acid (4.2.4) and heat to dissolve; add about 200 mL of water, and dropwise add ammonia water (4.2.12), until Congo red test paper changes from blue to purple. Cool, transfer to a 1,000 mL volumetric flask, use water to dilute to the scale, and mix well. 4.3 Instruments and Equipment All glassware shall conform to Class A as specified in GB/T 12805 and GB/T 12806. 4.4 Sampling and Sample Preparation Conduct sampling and sample preparation in accordance with GB/T 20066 and appropriate national standards. 4.5 Analytical Procedures 4.5.3.3 Separation of precipitate 4.5.3.3.1 Acidity adjustment Add 100 mL of complexing agent solution (4.2.15) to the test solution obtained in 4.5.3.2.1 or 4.5.3.2.2.Use ammonia solution (4.2.12) and sulfuric acid (4.2.8) to adjust the pH of the test solution to 4 ~ 5 [if tungsten-containing test portions precipitate, first add ammonia solution (4.2.11) to make it alkaline, heat to dissolve the tungstic acid precipitate, cool, and use sulfuric acid (4.2.8) and ammonia solution (4.2.12) to adjust the pH of the test solution to 4 ~ 5]. If the test solution is turbid at this point, heat it to boiling, until it becomes clear. Cool, and then adjust the pH of the test solution to 4 ~ 5 again. 4.5.3.3.2 Precipitation and its dissolution Transfer the test solution (see 4.5.3.3.1) to a 400 mL plastic beaker, add a small amount of paper pulp, and while stirring, add 100 mL of sodium fluoride solution (4.2.13). Thoroughly stir for 5 min, let stand for 40 min, use slow-speed filter paper containing a small amount of paper pulp to filter it, and use sodium fluoride solution (4.2.14) to wash it 7 ~ 8 times. Discard the filtrate. Transfer the precipitate and filter paper to the original glass beaker, immediately add 20 mL of hydrochloric acid-boric acid mixed acid (4.2.16) to dissolve the precipitate (this shall be immediately added, otherwise the precipitate will not completely dissolve). Add 20 mL ~ 25 mL of nitric acid (4.2.5), boil to break the filter paper (without covering the watch glass). Slightly cool, add 7 mL of perchloric acid (4.2.6), heat to evaporate until fuming and nearly dry. Slightly cool and add 50 mL of water to dissolve the salts. 4.5.3.4 Titration Add an appropriate amount of EDTA solution (4.2.20) to the test solution (see 4.5.3.3.2) in accordance with the aluminum content (for 1 mg aluminum, add 2 mL of EDTA solution), with an excess of 5 mL. Heat it to boiling for 2 ~ 3 minutes, add 2 drops of 2,4-dinitrophenol solution (4.2.18), and dropwise add ammonia solution (4.2.12), until the test solution turns slightly yellow. Continue boiling for 1 ~ 2 minutes, and cool [if the yellow color of the test solution fades at this time, dropwise add ammonia solution (4.2.12), until the test solution is slightly yellow]. Add 20 mL of acetic acid-ammonium acetate buffer solution (4.2.17) and 4 drops of xylenol orange solution (4.2.19). Use zinc standard solution (4.2.21) to titrate the test solution, until it turns purple red (not counting the milliliters). Add 1 g ~ 2 g of sodium fluoride (4.2.2), heat to boiling for 2 min ~3 min, and cool to room temperature [if the test solution turns purple red, dropwise add hydrochloric acid (4.2.4), until the purple-red color just fades]. Add 10 mL of acetic acid-ammonium acetate buffer solution (4.2.17) and 1 ~ 2 drops of xylenol orange solution (4.2.19). Use zinc standard solution (4.2.21) to titrate it, until it turns purple red, which is the endpoint. 4.6 Result Calculation The aluminum content wAl, expressed as mass fraction (%), is calculated in accordance with Formula (1). ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
