SH/T 0176-1992 Determination of Peroxide Value of Jet Fuels

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Card type: Test method

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

• Standard number: SH/T 0176-92
• Full name: Determination of Peroxide Value of Jet Fuels
• English name: not provided in the available source
• Replacement relationship: replaces ZB E31 005-88
• Other: the source text marks "(2〕)〕year confirmed)" — requires confirmation against the source standard (source-text extraction), the confirmation year cannot be identified
• Reference adoption: ASTM D 3703-85 "Determination of Peroxide Value of Aviation Turbine Fuels"

2. Scope of application and non-applicability

• Scope of application: This standard applies to jet fuels.
• Not applicable: not provided in the available source.

3. Method principle

Based on the release of active oxygen by peroxides in an acidic medium, quantitative analysis is carried out by the iodometric method. Taking an alkyl peroxide as an example, the reaction equation is as follows (the source text source-text extraction contains noise, the equation coefficients require confirmation): ROOH + 2KI + … → ROH + 2NaI + … + 2KOH

A certain amount of sample is dissolved in 1,1,2- trichloro-1,2,2- trifluoroethane or carbon tetrachloride, potassium iodide solution is added, the peroxides in the sample are reduced by potassium iodide, releasing a certain amount of iodine, which is titrated with a standard sodium thiosulfate volumetric solution, and the result is calculated as the peroxide value, expressed as ppm. Note: In case of dispute, 1,1,2- trichloro-1,2,2- trifluoroethane shall be the reference.

4. Reagents and materials (purity / preparation)

• 4.1 Potassium iodide: analytical reagent.
• 4.2 1,1,2- trichloro-1,2,2- trifluoroethane or carbon tetrachloride: analytical reagent.
• 4.3 Glacial acetic acid: analytical reagent.
• 4.4 Sodium thiosulfate: analytical reagent.
• 4.5 Potassium dichromate: primary standard reagent.
• 4.6 Starch: weigh 1 g starch and dissolve it in 100 mL boiling distilled water (to prevent spoilage, a few milliliters of mercuric iodide may be added), to prepare 10 g/L starch indicator solution.
• 4.7 Sodium carbonate: analytical reagent.
• 4.8 Hydrochloric acid: analytical reagent.
• 4.9 Trichloromethane (chloroform): analytical reagent.

Solution preparation in the preparatory work

• 6.1.1 c(1/6K₂Cr₂O₇)=0.1 mol/L Potassium dichromate primary standard solution: recrystallize potassium dichromate twice from aqueous solution, and dry at 120℃ to constant weight, weigh 2.4528 g and place in a 500 mL volumetric flask, dissolve in water and dilute to the mark.
• 6.1.2 c(1/6K₂Cr₂O₇)=0.01 mol/L Potassium dichromate primary standard solution: accurately measure 100 mL c(1/6K₂Cr₂O₇)=0.1 mol/L potassium dichromate primary standard solution, place in a 1000 mL volumetric flask, dilute with water to the mark.
• 6.2 c(Na₂S₂O₃)=0.1 mol/L Preparation and standardization of sodium thiosulfate standard volumetric solution:
  • 6.2.1 Preparation: weigh 12.5 g sodium thiosulfate (Na₂S₂O₃·5H₂O) and 0.1 g sodium carbonate, dissolve in 500 mL boiled and cooled distilled water, let stand for more than one week, then standardize with c(1/6K₂Cr₂O₇)=0.1000 mol/L potassium dichromate primary standard solution.
  • 6.2.2 Standardization: accurately measure with a pipette 40 mL c(1/6K₂Cr₂O₇)=0.1 mol/L potassium dichromate primary standard solution and place in an iodine flask, then add 40 mL distilled water, then add 3 g potassium iodide, 2 g sodium sulfate and 5 mL hydrochloric acid, cover with a stopper and shake, after mixing, let stand in the dark for 10 min, titrate with sodium thiosulfate solution until pale yellow, add 2 mL starch indicator solution, continue titrating until the blue color disappears and a bright green color appears, which is the endpoint, and simultaneously carry out a blank test.
  • Concentration calculation formula (1): c(Na₂S₂O₃) = c(1/6K₂Cr₂O₇) × V₂ / (V₁ − V₀)
    • c(1/6K₂Cr₂O₇): actual concentration of the potassium dichromate primary standard solution, mol/L
    • V₁: volume of sodium thiosulfate solution used, mL
    • V₀: volume of sodium thiosulfate solution used in the blank test, mL
    • V₂: volume of potassium dichromate primary standard solution, mL
  • The difference between two repeated standardization results shall not be greater than 0.0004 mol/L.
  • Note: Frequently check the concentration of c(Na₂S₂O₃)=0.1 mol/L sodium thiosulfate standard volumetric solution, its change shall not exceed 0.0005 mol/L.
• 6.3 c(Na₂S₂O₃)=0.005 mol/L Preparation of sodium thiosulfate standard volumetric solution: accurately measure 100 mL c(Na₂S₂O₃)=0.1 mol/L sodium thiosulfate standard volumetric solution, place in a 2000 mL volumetric flask, dilute with water to the mark.
• 6.4 Preparation of potassium iodide solution: weigh 120 g potassium iodide and dissolve in 100 mL distilled water, and decolorize the solution as follows: place 1 mL potassium iodide solution, 50 mL water and 5 mL starch indicator solution in a 300 mL flask, cover with nitrogen or carbon dioxide. If a blue color appears, add c(Na₂S₂O₃)=0.005 mol/L sodium thiosulfate standard volumetric solution with a microburette until the color just disappears. According to the calculation, add a sufficient amount of sodium thiosulfate standard volumetric solution to the main potassium iodide solution to convert all free iodine to iodide. In the normal preparation of potassium iodide solution, when the starch indicator solution is added to 1 mL potassium iodide solution, no blue color should appear, then add 1 drops of c(1/6K₂Cr₂O₇)=0.01 mol/L potassium dichromate primary standard solution and 2 drops of hydrochloric acid, a blue color should appear, finally add chloroform to the prepared potassium iodide solution so that it is stored under a chloroform layer.
• 6.5 Preparation of glacial acetic acid solution: mix 4 mL hydrochloric acid with 996 mL glacial acetic acid.

5. Instruments and equipment

• 5.1 Iodine flask: 500 mL.
• 5.2 Burette: 25 or 10 mL.
• 5.3 Pipette: 2 mL.

6. Recommended operating conditions

• Sample weighing amount according to the following table (the source table source-text extraction contains noise, values require confirmation):

(In the source table, values such as "10" and "5" appear, and their correspondence to the intervals requires confirmation (source-text extraction))

• Aeration conditions: pass nitrogen or carbon dioxide so that it vigorously passes through the solution for 1 min, reduce the gas flow rate to 1 bubbles per second.
• Standing in the dark: 5 min 13 s (the source text is "5mi n 1 3s", requires confirmation (source-text extraction)).
• The disappearance of the blue color at the titration endpoint shall be maintained for at least 30 s.

7. Sampling and sample preparation

• Weigh an appropriate sample amount according to the table in Article 7.1.
• Place the weighed sample in a 500 mL iodine flask that has been previously flushed with nitrogen or carbon dioxide gas.

8. Analytical procedure

• 7.2 Place the weighed sample in a 500 mL iodine flask that has been previously flushed with nitrogen or carbon dioxide gas, add 25 mL 1,1,2- trichloro-1,2,2- trifluoroethane or carbon tetrachloride, pass nitrogen or carbon dioxide so that it vigorously passes through the solution for 1 min, reduce the gas flow rate to 1 bubbles per second, add 20 mL glacial acetic acid solution and continue aeration, add 2 mL potassium iodide solution, immediately close the stopper tightly, shake vigorously for 30 s. Place in the dark and let stand for 5 min 13 s (requires confirmation (source-text extraction)).
• 7.3 After the reaction is completed, add 100 mL distilled water, titrate with c(Na₂S₂O₃)=0.005 mol/L sodium thiosulfate standard volumetric solution until pale yellow, then add 5 mL starch indicator solution, continue titrating until the blue color disappears, the disappearance of the blue color shall be maintained for at least 30 s, which is the endpoint.
• 7.4 For each test, a blank test must be carried out on the reagents. The test procedure is the same as that for the test sample except that no sample is added.

9. Qualitative and quantitative determination and calculation formula

The peroxide value X (ppm) of the sample is calculated according to formula (2):

X = (V₃ − V₄) × c₁ × 1000 × 8 / m

Where:

• V₃: the volume of sodium thiosulfate standard titration solution consumed when titrating the test sample, mL
• V₄: the volume of sodium thiosulfate standard titration solution consumed when titrating the blank, mL
• c₁: the actual concentration of the sodium thiosulfate standard titration solution, mol/L
• 8: 1/2 atomic weight of oxygen
• m: the mass of the test sample, g

(the original formula source-text extraction has typographical noise, and the symbol correspondences require confirmation against the source standard (source-text extraction))

10. Precision

The reliability of the test results is judged by the following provisions (95% confidence level).

• 9.1 Repeatability: the difference between two results obtained by the same operator from repeated determinations shall not be greater than 0.15 X₁, where X₁ is the arithmetic mean of the two repeated results.
• 9.2 Reproducibility: the difference between results submitted by two laboratories shall not be greater than 0.60 X₂, where X₂ is the arithmetic mean of the results submitted by the two laboratories.

11. Report

not provided in the available source.

12. Normative References

• ASTM D 3703-85 "Determination of Peroxide Value of Aviation Turbine Fuel" (referenced and adopted)

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