GB/T 259-1988 Determination of water-soluble acids and alkalis in 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 title / replacement relationship

• Standard number: GB/T 259-88 (the original cover is marked as "Gs/T 259[unreadable separator]88", which is source-text extraction noise, requires confirmation against the source standard (source-text extraction))
• Chinese title: Determination of water-soluble acids and alkalis in petroleum products
• English title: Petroleum products - Determination of water-soluble acids and alkalis (the original reads "snluhle acids and alkalis", which is source-text extraction noise, requires confirmation against the source standard (source-text extraction))
• Replacement relationship: replaces GB 259-77
• UDC: 665.52 :543-06
• Approval/implementation: approved by China Petrochemical Corporation 1988-03-14, implemented on 1989-03-01

2. Scope of application and non-applicability

• Applicable to the determination of water-soluble acids or water-soluble alkalis in liquid petroleum products, additives, lubricating greases, paraffin wax, ozokerite, and wax-containing components.
• Not applicable: not provided in the available source.

3. Method principle

Use distilled water or aqueous ethanol solution to extract water-soluble acids or alkalis from the sample, then respectively use methyl orange or phenolphthalein indicator to check the color change of the extract, or use a pH meter to determine the pH value of the extract, so as to judge whether water-soluble acids or alkalis are present.

4. Reagents and materials (purity / preparation)

Reagents

• Methyl orange: prepare as 0.02% methyl orange aqueous solution (the original reads "0.02[unreadable unit]", which is source-text extraction noise, requires confirmation against the source standard (source-text extraction))
• Phenolphthalein: prepare as 1% phenolphthalein ethanol solution
• 95% ethanol: analytical reagent

Materials

• Filter paper: industrial filter paper
• Solvent naphtha: complies with the provisions of SH 0004 solvent naphtha for the rubber industry
• Distilled water: complies with the grade three water provisions of GB/T 6682 "Water specifications and test methods for analytical laboratory use"

5. Apparatus and equipment

• 2.1 Separatory funnel: 250 or 500 mL
• 2.2 Test tube: diameter 15–20 mm, height 140–150 mm, made of colorless glass
• 2.3 Funnel: ordinary glass funnel
• 2.4 Graduated cylinder: 25, 50 and 100 mL
• 2.5 Conical flask: 100 and 250 mL
• 2.6 Porcelain evaporating dish
• 2.7 Electric heating plate and water bath
• 2.8 pH meter: with glass-silver chloride electrode (or glass-calomel electrode), precision pH<0.01 pH

6. Recommended operating conditions

• Heating temperature: 50~60 ℃ (light petroleum products such as gasoline and solvent naphtha are not heated)
• Shaking time: 5 min
• pH meter electrode immersion depth: 10~12 mm (the original reads "]10^-12 mm", which is source-text extraction noise, requires confirmation against the source standard (source-text extraction))
• Arbitration test: carried out according to the 5.5.1 pH meter method

7. Sampling and sample preparation

4.1 Preparation of test sample

• 4.1.1 Place the sample into a glass bottle, not exceeding three quarters of its volume, shake for 5 min; viscous or paraffin wax samples should be preheated to 50~60 ℃ before shaking.
• 4.1.2 When the sample is lubricating grease, use a scraper to scrape off the surface layer of the sample (3~5 mm), then take approximately equal amounts of sample from at least three locations not close to the container wall and place them into a porcelain evaporating dish, and carefully stir evenly with a glass rod.
• 4.2 95% Ethanol must be tested with methyl orange and phenolphthalein indicators, or with a pH meter, to be neutral before use.

8. Analysis procedure

5.1 Liquid petroleum products

Place 50 mL sample and 50 mL distilled water into a separatory funnel, heat to 50–60 ℃; light petroleum products such as gasoline and solvent naphtha are not heated. For petroleum products with kinematic viscosity at 50 ℃ greater than 75 mm²/s, they should first be mixed with 50 mL gasoline at room temperature, then add 50 mL distilled water heated to 50–60 ℃. Gently shake the test solution in the separatory funnel for 5 min, emulsification is not allowed. Release the lower aqueous layer after clarification, filter through filter paper, and filter into a conical flask.

5.2 Lubricating grease, paraffin wax, ozokerite and wax-containing components

Take 50 g pre-melted sample, weigh to the nearest 0.01 g, place it in a porcelain evaporating dish or conical flask, then inject 50 mL distilled water, and boil until completely melted. After cooling to room temperature, carefully pour the lower aqueous layer into a funnel with filter paper, and filter into a conical flask. For products that have solidified (such as paraffin wax and ozokerite, etc.), first pierce the wax layer with a glass rod.

5.3 Additive products

Inject 10 mL sample and 40 mL solvent naphtha into a separatory funnel, then add 50 mL distilled water heated to 50~60 ℃. Shake the separatory funnel for 5 min, after clarification separate the lower aqueous layer, filter through a funnel with filter paper, and filter into a conical flask.

5.4 Emulsification treatment

If emulsification occurs when the petroleum product is mixed with water, that is, when water is used to extract water-soluble acids or alkalis, then use 50~60 ℃ 1:1 95% aqueous ethanol solution instead of distilled water for treatment, and subsequent steps are carried out according to clause 5.1 or clause 5.3. Note: When testing diesel oil, alkali-washed lubricating oil, additive-containing lubricating oil, and crude residual petroleum products, if the water extract of the sample shows an alkaline reaction to phenolphthalein (possibly caused by hydrolysis of saponifiable matter), the procedure in this clause may also be followed.

5.5 Determination

5.5.1 Determination of water-soluble acids or alkalis with a pH meter

Inject 30–50 mL extract into a beaker, with an electrode immersion depth of 10–12 mm, and determine the pH value according to the pH meter operating requirements. Determine whether water-soluble acids or alkalis are present in the aqueous or aqueous ethanol solution of the sample extract according to the table below.

5.5.2 Determination of water-soluble acids or alkalis with indicators

Place 1~2 mL extract into two test tubes respectively, add 2 drops of methyl orange solution to the first test tube, and compare it with a third test tube containing the same volume of distilled water and methyl orange solution. If the extract is rose-colored, it indicates that water-soluble acid is present in the tested petroleum product. Add 3 drops of phenolphthalein solution to the second test tube containing the extract. If the solution is rose-colored or red, it indicates that water-soluble alkali is present. When the extract with methyl orange or phenolphthalein as indicator does not show rose color or red, it is considered that no water-soluble acid or alkali is present.

5.5.3 Arbitration

When there is disagreement in the quality evaluation of petroleum products, the arbitration test for water-soluble acids or alkalis is carried out according to 5.5.1.

9. Qualitative and quantitative determination and calculation formulas

• Qualitative judgment: judge whether water-soluble acids or alkalis are present according to the 5.5.1 pH value classification table or the color change of the 5.5.2 indicator.
• Quantitative calculation: no calculation formula is provided in the available source.

10. Precision

• 6.1 This precision specification applies only to the pH meter method.
• 6.2 The difference between two results obtained by the same operator shall not exceed 0.05 pH.

11. Report

Take the arithmetic mean of two pH values from repeated determinations as the test result.

12. Referenced documents

• SH 0004 Solvent naphtha for the rubber industry
• GB/T 6682 "Water specifications and test methods for analytical laboratory use"
• Reference adoption of Soviet national standard ГОСТ 6307-75 "Determination of water-soluble acids and alkalis in petroleum products" (the original reads "FOOT6307-75", which is source-text extraction noise, requires confirmation against the source standard (source-text extraction))

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 Q&A