GB/T 2012-1989 Aromatic hydrocarbon acid wash test method

AI-translated method card — human verification pending. This is not an official translation of the standard. Unclear source values remain unverified; check the original standard and product certificate before use.

Card type: Test method

1. Method number / full name / English name / replacement relationship

• Standard number: GB 2012—89
• Chinese name: Aromatic hydrocarbon acid wash test method
• English name: Aromatic hydrocarbons—Test method of acid wash
• Replacement relationship: replaces GB 2012—80
• Adoption relationship: This standard equivalently adopts the international standard ISO 5274-1979 "Aromatic hydrocarbon acid wash test method"
• Approval/implementation: approved by China Petrochemical Corporation 1989-03-17, implemented on 1990-04-01

2. Scope of application and non-applicability

• This standard specifies the test method for aromatic hydrocarbon acid wash colorimetric comparison.
• This standard applies to aromatic hydrocarbons.
• Not applicable: not provided in the available source.
• Safety note (original text): Aromatic hydrocarbons are toxic upon inhalation, ingestion, or skin contact; volatile aromatic hydrocarbons are highly flammable; relevant safety and health issues should be noted.

3. Method principle

Under specified conditions, shake an equal volume of the sample with 95% (m/m) sulfuric acid, and compare the color of the acid layer with that of the standard colorimetric solution.

4. Reagents and materials (purity / preparation)

• 4.1 Potassium dichromate: analytical reagent; grind potassium dichromate finely and dry at 120°C to constant weight.
• 4.2 Sulfuric acid: analytical reagent; prepare solutions with a concentration of 95±0.5% (m/m) and about 98% (m/m).
• 4.3 Potassium permanganate: analytical reagent; prepare a solution of 3.2 g/L (original text source-text extraction is "3.28/L", requires confirmation against the source standard (source-text extraction)).
• 4.4 Twice-distilled water: add a small amount of potassium permanganate to distilled water and redistill in a glass distillation flask.
• 5.1 Preparation of standard colorimetric solution:
  • 5.1.1 The standard colorimetric solution has oxidizing properties; contact with any organic matter should be avoided during preparation and storage. When preparing and storing the solution, use grease-free and dust-free glass-stoppered colorimetric tubes.
  • 5.1.2 Prepare a stock dilute acid solution containing equal volumes of distilled water and sulfuric acid at a concentration of about 98% (m/m). During preparation, carefully add the sulfuric acid to the water with uniform stirring. Allow the solution to reach room temperature before use.
  • 5.1.3 To 100 mL of the stock dilute acid solution, add 2 drops (0.1 mL) of potassium permanganate solution to test for substances that can be oxidized. The color of potassium permanganate should not disappear within 5 min.
  • 5.1.4 Take a portion of the stock dilute acid solution to prepare a stock potassium dichromate solution with a potassium dichromate content higher than the highest required by the standard colorimetric solution. Dilute the stock potassium dichromate solution with an appropriate amount of stock dilute acid solution as needed to prepare the standard colorimetric solution (refer to Appendix A). The highest concentration of the potassium dichromate solution is 10 g of potassium dichromate per 1000 mL of stock dilute acid solution; at this concentration, the dissolution of potassium dichromate is very slow.
  • 5.1.5 The standard colorimetric solution should be prepared on the same day it is used.
  • 5.1.6 When not in use, the stock dilute acid solution, stock potassium dichromate solution, and standard colorimetric solution should all be stored in the dark.
• Appendix A Preparation of standard colorimetric solution (reference item):
  • A1 Grind potassium dichromate finely, dry at 120°C to constant weight, weigh 2.5±0.0002 g (the weighing tolerance is unclear in the source transcription and remains unverified), place in a clean beaker, first dissolve with 50 mL of distilled water, then add 50 mL of about 98% (m/m) sulfuric acid, then transfer to a 500 mL volumetric flask. Rinse the beaker with the stock dilute acid solution, transfer the rinse liquid into the volumetric flask, cool, dilute to the mark with the stock dilute acid solution, and mix well; this solution is called the stock potassium dichromate solution.
  • A2 According to Table A1, use a pipette or burette to take the stock potassium dichromate solution into a clean 100 mL volumetric flask, then add the stock dilute acid solution to dilute to the mark, and mix well. Place these standard colorimetric solutions separately into colorimetric tubes, cover with ground stoppers, and seal the ground joints with paraffin.
  • Table A1 Preparation of standard colorimetric solution (potassium dichromate content in standard colorimetric solution g/L | amount of stock potassium dichromate solution added mL | amount of stock dilute acid solution added mL):
    • 0.05 | 1 | 99
    • 0.10 | 2 | 98
    • 0.15 | 3 | 97
    • 0.20 | 4 | 96
    • 0.25 | 5 | 95
    • 0.30 | 6 | 94
    • 0.35 | 7 | 93
    • 0.40 | 8 | 92
    • 0.50 | 10 | 90
    • 0.60 | 12 | 88
    • 0.70 | 14 | 86
    • 0.80 | 16 | 84
    • 0.90 | 18 | 82
    • 1.00 | 20 | 80
    • 1.50 | 30 | 70
    • 2.00 | 40 | 60
    • 3.00 | 60 | 40
    • 4.00 | 80 | 20
    • 5.00 | 100 | 0

5. Instruments and equipment

• 3.1 Colorimetric tube: a cylinder with a glass ground stopper, made of thin-walled colorless glass. Height about 100 mm, inner diameter 13±0.5 mm (original text source-text extraction is "inner diameter 130.5 mm", requires confirmation against the source standard (source-text extraction)), wall thickness 1~2 mm. There are two scale lines around the colorimetric tube; the upper scale line is 70±1 mm from the outer bottom surface of the colorimetric tube (original text source-text extraction is "701 mm", requires confirmation against the source standard (source-text extraction)), and the lower scale line should bisect the volume from the inner bottom surface of the colorimetric tube to the upper scale line, with a difference of no more than 0.1 mL. All colorimetric tubes should be similar in color and other aspects.
• 3.2 Water bath: capable of controlling at 20±1°C (original text source-text extraction is "201°C", requires confirmation against the source standard (source-text extraction)).

6. Recommended operating conditions

• The test should not be conducted in direct sunlight.
• Water bath temperature: 20±1°C (original text source-text extraction is "201°C", requires confirmation against the source standard (source-text extraction)).
• Shaking: shake the colorimetric tube vigorously for 2 min±5 s (original text source-text extraction is "2 mint 5S", requires confirmation against the source standard (source-text extraction)).
• Standing: return the colorimetric tube to the water bath and let stand for 10 min±5 s (original text source-text extraction is "10mint 5 s", requires confirmation against the source standard (source-text extraction)).
• When visually comparing colors, it is best to place white paper behind the colorimetric tube to avoid interference from external light.

7. Sampling and sample preparation

• 6.4 Filter the sample and discard the first 10 mL of filtrate. Inject the filtered sample into the third colorimetric tube up to the lower scale line.

8. Analysis procedure

• 6.1 Clean the colorimetric tube with chromic acid cleaning solution, rinse with distilled water, and dry.
• 6.2 Prepare a potassium dichromate standard colorimetric solution according to the concentration specified in the sample product specification (accurate to 0.01 g per 1000 mL, original text source-text extraction is "0.018", requires confirmation against the source standard (source-text extraction)), and fill it to the upper scale line of one colorimetric tube.
• 6.3 Prepare another potassium dichromate standard colorimetric solution in the same way, with a concentration equal to the sum of the concentration of the standard colorimetric solution in the first colorimetric tube and the repeatability specified value (9.1) corresponding to that concentration (accurate to 0.01 g per 1000 mL, original text source-text extraction is "0.018", requires confirmation against the source standard (source-text extraction)). Fill this solution to the upper scale line of the second colorimetric tube.
• 6.4 Filter the sample and discard the first 10 mL of filtrate. Inject the filtered sample into the third colorimetric tube up to the lower scale line. Cover with a stopper and place in a water bath at 20±1°C. Use a suitable container, fill it with a certain amount of 95% (m/m) sulfuric acid, and place it in the water bath until it reaches the temperature of the water bath. Then inject 95% (m/m) sulfuric acid into the third colorimetric tube so that the liquid level of the contents reaches the upper scale line. Cover the stopper, shake the colorimetric tube vigorously for 2 min±5 s, return the colorimetric tube to the water bath, let stand for 10 min±5 s, and then immediately compare the color of the acid layer in the colorimetric tube with the standard colorimetric solutions in the above two colorimetric tubes under good light.
• When visually comparing colors, it is best to place white paper behind the colorimetric tube to avoid interference from external light.

9. Qualitative and quantitative and calculation formula

• No calculation formula is provided in the available source.
• Result determination (Chapter 8 Report): The result is reported as lighter than the standard colorimetric solution specified in the product standard; equal to the standard colorimetric solution specified in the product standard; although darker than the standard colorimetric solution specified in the product standard, but within the error range of precision; or darker than the standard colorimetric solution specified in the product standard.

10. Precision

Use the following provisions to judge the reliability of test results (95% confidence level).

• 7.1 Repeatability: The difference between two results obtained by the same operator in repeated measurements should not exceed the value listed in the table.
• 7.2 Reproducibility: The difference between two results submitted by different laboratories should not exceed the value listed in the table.
• Precision table (potassium dichromate content in standard colorimetric solution g/L | repeatability | reproducibility):
  • 0.1~0.4 | 0.05 | 0.1
  • 0.5 | 0.1 | 0.2
  • 1.0 | 0.1 | 0.2
  • 1.5 | 0.2 | 0.5
  • 2.0 | 0.4 | 0.6
  • 3.0 | 0.8 | 1.0
  • 5.0 | 2.0 | 1.8
  • Note ①: This standard has poorer precision for darker-colored samples.
  • Note ②: Some samples, due to longer storage time, tend to give higher results.
  • Note: In the precision table, the correspondence between the two rows “3.0 | 0.8 | 1.0” and “5.0 | 2.0 | 1.8” requires confirmation against the source standard (source-text extraction).

11. Report

The result is reported as lighter than the standard colorimetric liquid specified in the product standard; equal to the standard colorimetric liquid specified in the product standard; although darker than the standard colorimetric liquid specified in the product standard, but within the precision error range; or darker than the standard colorimetric liquid specified in the product standard.

12. Normative References

• ISO 5274-1979 Aromatic Hydrocarbons Acid Wash Test Method (equivalent adoption)
• GB 2012—80 (replaced)
• No other normative references are provided in the available source.

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Q&A Reference