GB/T 2432-1981 Determination of tetraethyl lead content in gasoline (complexometric titration)

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/T 2432-1981 (the standard designation is garbled in the source transcription and requires verification)
• Chinese name: Determination of tetraethyl lead content in gasoline (complexometric titration)
• English name: Gasoline-Determination of tetraethyl lead content--Complexometric titration
• Replacement relationship: From the date of implementation of this standard, the former Ministry of Petrochemical Industry ministerial standard SY 2106-78 "Determination of tetraethyl lead content in gasoline (complexometric titration)" is void.
• Confirmation information: Confirmed in 1988.
• Issuance/implementation: Issued by the National Bureau of Standards 1981-02-13, implemented on 1981-07-01.

2. Scope of application and non-applicability

• Applicable for the determination of tetraethyl lead content in gasoline.
• Not applicable: not provided in the available source.

3. Method principle

This method uses boiling hydrochloric acid to decompose tetraethyl lead in gasoline, generating lead chloride. Then an excess of disodium ethylenediaminetetraacetate standard solution is added to form a complex with lead ions. The excess disodium ethylenediaminetetraacetate standard solution is titrated with zinc chloride standard solution. Expressed as grams of tetraethyl lead per 1 kilograms of gasoline.

4. Reagents and materials (purity / preparation)

• Hydrochloric acid: analytical grade, prepared as 6N hydrochloric acid aqueous solution.
• Ammonia water: analytical grade.
• Hexamethylenetetramine: analytical grade.
• Zinc oxide: analytical grade or pure zinc granules (analytical grade).
• Disodium ethylenediaminetetraacetate: analytical grade, prepared as 0.02M disodium ethylenediaminetetraacetate standard solution.
• Xylenol orange indicator: prepared as 0.5% aqueous solution (valid for one month).

4.1 0.02M Preparation and standardization of zinc chloride standard solution

• 4.1.1 Weigh 1.628 grams of zinc oxide that has been ignited at 800℃ to constant weight, weighed to 0.0002 grams. Add 20 milliliters of 6N hydrochloric acid aqueous solution and 25 milliliters of distilled water to dissolve it, then transfer to a 1000 milliliter volumetric flask, dilute to the mark with distilled water, and mix well.
• The molar concentration M₁ of the zinc chloride standard solution is calculated according to formula (1): M₁ = G / 81.38 Where: G— weight of zinc oxide, grams; 81.38— grams per mole of zinc oxide.
• 4.1.2 Treat pure zinc granules with 6N hydrochloric acid aqueous solution, remove surface oxides, wash several times with distilled water, dry at 150℃, weigh 1.3 grams, weighed to 0.0002 grams. Dissolve with 20 milliliters of 6N hydrochloric acid aqueous solution, then transfer to a 1000 milliliter volumetric flask, dilute to the mark with distilled water, and mix well.
• The molar concentration M₂ of the zinc chloride standard solution is calculated according to formula (2): M₂ = G' / 65.38 Where: G'—weight of zinc granules, grams; 65.38— grams per mole of zinc.

4.2 0.02M Preparation and standardization of disodium ethylenediaminetetraacetate standard solution

• 4.2.1 Preparation: Weigh 8 grams of disodium ethylenediaminetetraacetate, dissolve in 1000 milliliters of distilled water, and mix well.
• 4.2.2 Standardization: Accurately measure 25 milliliters of disodium ethylenediaminetetraacetate standard solution into a conical flask, add 0.5% xylenol orange aqueous solution 5～6 drops, adjust with ammonia water until the solution turns peach-red, then adjust with 6N hydrochloric acid aqueous solution until bright yellow, then add 6N hydrochloric acid aqueous solution 0.5 milliliters, add hexamethylenetetramine 1.5～2.0 grams, immediately titrate with 0.02M zinc chloride standard solution until the solution changes from yellow to peach-red, which is the endpoint.
• The molar concentration M₃ of the disodium ethylenediaminetetraacetate standard solution is calculated according to formula (3): M₃ = M₂·V₁ / 25 Where: M₂—molar concentration of the zinc chloride standard solution; V₁—volume of zinc chloride standard solution consumed during titration, milliliters; 25— volume of disodium ethylenediaminetetraacetate standard solution measured, milliliters.
• Each standardization shall be performed at least three times; the difference between the results of each determination shall not exceed 0.2% of the arithmetic mean, otherwise it must be discarded. (That is: |maximum - minimum| / average × 100% ≤ 0.2%)
• Take the arithmetic mean of not fewer than three titration results as the molar concentration of the disodium ethylenediaminetetraacetate standard solution.

5. Instruments and equipment

• Burette: 25 milliliters.
• Pipette: 25 and 50 milliliters.
• Ground-glass stoppered conical flask: 500 milliliters.
• Graduated cylinder: 50 and 100 milliliters.
• Thermometer: 0～100℃, graduation 1℃ (the source text says "graduation 10 C", requires confirmation against the source standard (source-text extraction)).
• Petroleum hydrometer: 0.710～0.770 grams/milliliter.
• Volumetric flask: 1000 milliliters.
• Electric heating plate or closed electric furnace: 300 watts.
• Condenser tube: five-bulb with ground joint matching the conical flask.

6. Recommended operating conditions

• Heating extraction: Start timing from the boiling of the mixed liquid in the stoppered conical flask, stop heating after 25 minutes.
• Cooling: Rinse the condenser tube and the inner wall of the stoppered conical flask with 40～50 milliliters of distilled water, cool in cold water to 25～30℃.
• Titration: Titrate with 0.02M zinc chloride standard solution until the extract changes from yellow to peach-red, which is the endpoint.
• Safety note: Heating extraction should be carried out in a fume hood or a rubber tube with a cork stopper should be attached to the upper end of the condenser tube, with the lower end of the rubber tube inserted into a buffer gas bottle, and the rubber tube leading from the buffer gas bottle inserted into a bottle containing sodium hydroxide aqueous solution.

7. Sampling and sample preparation

• In a clean stoppered conical flask, use a pipette to inject 50 milliliters of sample.
• Add 30 milliliters of hydrochloric acid, attach a reflux condenser, place on an electric heating plate or closed electric furnace, and heat for extraction.

8. Analytical procedure

• 5.1 In a clean stoppered conical flask, use a pipette to inject 50 milliliters of sample, add 30 milliliters of hydrochloric acid, attach a reflux condenser, place on an electric heating plate or closed electric furnace, and heat for extraction. Start timing from the boiling of the mixed liquid in the stoppered conical flask, stop heating after 25 minutes. Rinse the condenser tube and the inner wall of the stoppered conical flask with 40～50 milliliters of distilled water, cool in cold water to 25～30℃.
• 5.2 To the cooled extract, accurately add 25 milliliters of 0.02M disodium ethylenediaminetetraacetate standard solution using a burette, add 0.5% xylenol orange aqueous solution 5～6 drops; at this time the extract is yellow, then adjust with ammonia water until the extract turns peach-red, then adjust with 6N hydrochloric acid aqueous solution until yellow, then continue to add 6N hydrochloric acid aqueous solution 0.5 milliliters, then add hexamethylenetetramine 1.5～2 grams, immediately titrate with 0.02M zinc chloride standard solution until the extract changes from yellow to peach-red, which is the endpoint.

9. Qualitative and quantitative determination and calculation formula

The tetraethyl lead content X in the sample, expressed as grams of tetraethyl lead per 1 kilograms of sample, is calculated according to formula (4):

X = [ (V·M₃ - V₂·M₂) × 323.2 ] / (V₀·ρ)

Where:

• V— volume of disodium ethylenediaminetetraacetate standard solution, milliliters;
• M₃—molar concentration of disodium ethylenediaminetetraacetate standard solution;
• V₂—volume of zinc chloride standard solution consumed during titration, milliliters;
• M₂—molar concentration of zinc chloride standard solution;
• V₀—volume of sample, milliliters;
• ρ— density of sample at test temperature, grams/milliliter;
• 323.2— molecular weight of tetraethyl lead.

(Note: The formula part source-text extraction in the source text is severely incomplete; the above formula structure is restored based on context and common complexometric titration calculation formulas, and the specific symbol correspondence requires confirmation against the source standard (source-text extraction).)

10. Precision

The difference between two repeated determination results shall not exceed the following values:

11. Report

Take the arithmetic mean of two repeated determination results as the determination result.

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 Q&A