GB/T 264-1983 Determination of Acid Number of Petroleum Products

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 title / English name / replacement relationship

• Standard number: GB/T 264-83 (the original cover is marked as CB/T264-83, requires confirmation against the source standard (source-text extraction); the body page header is GB/T264 83)
• Chinese title: Determination of Acid Number of Petroleum Products
• English name: Petroleum products—Determination of acid number
• Replacement relationship: replaces GB264-77
• Other: UDC655.5:543, 541.5; (confirmed in 1991); first published in 1964

2. Scope of application and non-applicability

• Applicable to the determination of the acid number of petroleum products.
• Not applicable: not provided in the available source.

3. Method principle

• The acidic components in the sample are extracted with boiling ethanol, and then titrated with potassium hydroxide ethanol solution.
• Definition: the number of milligrams of potassium hydroxide required to neutralize 1 grams of petroleum product is called the acid number.

4. Reagents and materials (purity / preparation)

• 3.1 Potassium hydroxide: analytical reagent, prepared as 0.05N potassium hydroxide ethanol solution.
• 3.2 95% ethanol: analytical reagent (the original text says “analytical alcohol”, requires confirmation against the source standard (source-text extraction)).
• 3.3 Alkali blue 6B: weigh 1 grams of alkali blue, add it to 50 milliliters of boiling 95% ethanol, reflux in a water bath for 1 hours, cool, and filter. If necessary, neutralize the boiled clear filtrate with 0.05N potassium hydroxide ethanol solution or 0.05N hydrochloric acid solution until the addition of 12 drops of alkali solution can make the indicator solution turn light red and then return to blue after cooling; some indicator preparations only become sensitive in color change after such treatment.
• 3.4 Cresol red (the original text contains garbled indicator names, requires confirmation against the source standard (source-text extraction)): weigh 0.1 grams of cresol red (weighed to 0.01 grams), grind finely, dissolve in 100 milliliters of 95% ethanol, boil and reflux in a water bath for 5 minutes, and while hot titrate with 0.05N potassium hydroxide solution until the cresol red solution changes from orange-red to deep red and can return to orange-red after cooling.

5. Apparatus and equipment

• 2.1 Conical flask: 250 or 300 milliliters
• 2.2 Spherical reflux condenser: about 300 millimeters long
• 2.3 Microburette: 2 milliliters, graduation 0.02 milliliters
• 2.4 Electric heating plate or water bath

6. Recommended operating conditions

• Ethanol boiling: 5 minutes (to remove carbon dioxide)
• Sample boiling: 5 minutes
• Indicator addition amount: 0.5 milliliters of alkali blue 6B (or cresol red) solution
• Titration temperature: titrate while hot
• Time limit: the time from stopping heating the conical flask to reaching the titration endpoint shall not exceed 3 minutes
• Other: not provided in the available source

7. Sampling and sample preparation

• 4.1 Use a clean, dry conical flask to weigh 8~10 grams of sample (the original text says “8*10 grams”, requires confirmation against the source standard (source-text extraction)), weighed to 0.2 grams.
• Other: not provided in the available source.

8. Analysis procedure

• 4.2 In another clean, water-free conical flask, add 95% ethanol 50 milliliters, and attach a reflux condenser. While shaking continuously, boil the 95% ethanol for 5 minutes to remove carbon dioxide dissolved in the 95% ethanol.
• To the boiled 95% ethanol, add 0.5 milliliters of alkali blue 6B (cresol red) solution, and while hot neutralize with 0.05N potassium hydroxide ethanol solution until the solution changes from blue to light red (or from yellow to purple-red). For ethanol that is already light red (purple-red) before neutralization, if it is to be used to determine the acid number of samples with a relatively small acid number, a few drops of 0.05N dilute hydrochloric acid may be added in advance to neutralize the ethanol to just slightly acidic, and then neutralize according to the above procedure until the solution changes from blue to light red (or from yellow to purple-red).
• 4.3 Pour the neutralized 95% ethanol into the conical flask containing the weighed sample, and attach a reflux condenser. While shaking continuously, boil the solution for 5 minutes.
• To the boiled mixture, add 0.5 milliliters of alkali blue 6B (or cresol red) solution, and while hot titrate with 0.05N potassium hydroxide ethanol solution until the 95% ethanol layer changes from blue to light red (or from yellow to purple-red).
• For samples that cannot show light red (or purple-red) at the titration endpoint, it is permissible to take the point at which the original color of the mixture begins to change significantly as the endpoint.
• During each titration, the time from stopping heating the conical flask to reaching the titration endpoint shall not exceed 3 minutes.

9. Qualitative and quantitative determination and calculation formula

• 5.1 The acid number X of the sample, expressed in milligrams KOH/ grams, is calculated according to the following formula:
  • X = V·T / G
  • T = 56.1 × N
• Where:
  • V — volume of potassium hydroxide ethanol solution consumed during titration, milliliters;
  • G — weight of the sample, grams;
  • T — titer of the potassium hydroxide ethanol solution, milligrams KOH/ milliliters;
  • 56.1 — gram equivalent of potassium hydroxide;
  • N — normality of the potassium hydroxide ethanol solution, N.

10. Precision

• 6.1 Repeatability (95% confidence level, the difference between two results obtained by the same operator in repeated determinations shall not exceed the following values):
  • Range 0.00—0.1 milligrams KOH/ grams: repeatability 0.02 milligrams KOH/ grams
  • Range greater than 0.1—0.5 milligrams KOH/ grams: repeatability 0.05 milligrams KOH/ grams
  • Range greater than 0.5—1.0 milligrams KOH/ grams: repeatability 0.07 milligrams KOH/ grams
  • Range greater than 1.0—2.0 milligrams KOH/ grams: repeatability 0.10 milligrams KOH/ grams
• 6.2 Reproducibility (the difference between two results submitted by two laboratories shall not exceed the following values):
  • Range 0.00—0.1 milligrams KOH/ grams: reproducibility 0.04 milligrams KOH/ grams
  • Range greater than 0.1—0.5 milligrams KOH/ grams: reproducibility 0.10 milligrams KOH/ grams
  • Range greater than 0.5—1.0 milligrams KOH/ grams: reproducibility 15% of the average value
  • Range greater than 1.0—2.0 milligrams KOH/ grams: reproducibility 15% of the average value
• Note: This precision was obtained in 1980—1981 by statistical testing with 6 samples in 13 laboratories, and by processing and analyzing the test results (the original wording about obtaining the results is garbled, requires confirmation against the source standard (source-text extraction)).

11. Report

• 7.1 Take the arithmetic mean of the two results of repeated determination as the acid number of the sample.

12. Referenced documents

• Not 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-reference questions and answers