SH/T 0135-1992 Determination of Peroxide Value of Liquid Paraffin

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Card type: Test method

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

• Standard number: SH/T 0135-92
• Chinese title: Determination of Peroxide Value of Liquid Paraffin
• English title: not provided in the available source
• Replacement relationship: From the date of implementation of this standard, the former national standard GB 11083-89 "Determination of Peroxide Value of Liquid Paraffin" is void.
• Adoption relationship: This standard equivalently adopts the American Society for Testing and Materials standard ASTM D2340-82 "Test Method for Peroxides in Styrene Monomer".
• Technical committee: Technical committee responsibility of Fushun Research Institute of Petroleum and Petrochemicals.
• Drafting organization: Fushun Research Institute of Petroleum and Petrochemicals is responsible for drafting.
• Main drafter: Zhao Qingyou.
• Approval/implementation: Approved by China Petrochemical Corporation 1992-05-20, implemented on 1992-05-20.

2. Scope of application and non-applicability

• This standard specifies the iodometric determination of the peroxide value of liquid paraffin, with its content calculated as hydrogen peroxide.
• This standard applies to the determination of peroxide value in liquid paraffin.
• Not applicable: not provided in the available source.

3. Method principle

Add a certain amount of test sample to isopropanol and acetic acid solution, then add saturated sodium iodide isopropanol solution and heat. Peroxides present in the sample cause iodine to be quantitatively liberated from the sodium iodide solution, and the liberated iodine is titrated with sodium thiosulfate standard titration solution.

4. Reagents and materials (purity / preparation)

• 4.1 Isopropanol: analytical reagent, blank peroxide value less than 1.00.
• 4.2 Glacial acetic acid: analytical reagent.
• 4.3 Sodium iodide: analytical reagent.
• 4.4 Sodium thiosulfate: analytical reagent.
• 4.5 Water: distilled water or water of equivalent purity.
• 5.1 Preparation of saturated sodium iodide solution: weigh 100 g sodium iodide and measure 500 mL isopropanol, add to a 500 mL amber narrow-mouth bottle. Shake to fully dissolve the sodium iodide, then store in a dark place.
• 5.2.1 [c(Na2S2O3)=0.01 mol/L] Preparation of sodium thiosulfate standard titration solution: weigh 2.5 g sodium thiosulfate (Na2S2O3·5H2O) and 0.1 g sodium carbonate (Na2CO3), dissolve in water and dilute to 1 L. Standardize with potassium dichromate (K2Cr2O7) primary standard reagent.
• 5.2.2 [c(Na2S2O3)=0.005 mol/L] Preparation of sodium thiosulfate standard titration solution: accurately measure [c(Na2S2O3)=0.01 mol/L] sodium thiosulfate standard titration solution and mix uniformly with water in a volume ratio of 1:1.

5. Apparatus and equipment

• 4.1 Flask: 500 mL. Conical, equipped with a standard ground joint, with a straight condenser of length 200 mm. (requires confirmation against the source standard (source-text extraction): the original text says "straight condenser of length 200 two", the unit is suspected to be mm)
• 4.2 Electric furnace: flat-plate sealed type, 1000 W.
• 4.3 Microburette: 1～3 mL. (requires confirmation against the source standard (source-text extraction): the original text says "1 one 3mLa")
• 4.4 Pipette: 50 mL.
• 4.5 Stopwatch.

6. Recommended operating conditions

• The electric furnace should be preheated first to shorten the heating-up time.
• When the solution begins to boil, remove the flask from the electric furnace and cool at room temperature for about 1 min.
• Place on the electric furnace again and heat, maintaining gentle boiling for 10 min.
• Cooling: place the flask in a porcelain dish (or sink) containing tap water to cool, rinse the condenser with 5～10 mL distilled water, allowing the rinse liquid to flow into the flask, remove the condenser, and cover the ground stopper. To accelerate cooling, the porcelain dish may be moved into a water basin, adjust an appropriate water flow, and cool with running tap water for 10 min.
• Safety conditions: Because this test uses a large amount of flammable solvent, the laboratory must have fire prevention measures. No open flame is allowed during the test.

7. Sampling and test sample preparation

• 5.4 Take two clean 500 mL flasks, and respectively add 200 mL isopropanol and 10 mL glacial acetic acid.
• 5.5 Use a pipette to draw 50 mL test sample and add it to one of the flasks, marking this flask as "test sample". The flask without test sample is the "blank". To prevent bumping of the solution during heating, a few boiling stones may be added.
• During sampling, the density of the test sample ρ is used for calculation (see Section 9).

8. Analytical procedure

• 5.6 Attach condensers to the two flasks, pass cooling water through, and simultaneously place on the electric furnace to heat; to shorten the heating-up time, the electric furnace should be preheated first. When the solution begins to boil, remove the flasks from the electric furnace and cool at room temperature for about 1 min, then use a pipette to respectively take 50 mL saturated sodium iodide solution and add it to each flask from the top of the condenser.
• 5.7 Place the two flasks on the electric furnace again and heat, maintaining gentle boiling for 10 min, then remove from the electric furnace, place the flasks in a porcelain dish (or sink) containing tap water to cool, rinse the condenser with 5～10 mL distilled water, allowing the rinse liquid to flow into the flask, remove the condenser, and cover the ground stopper. To accelerate cooling, the porcelain dish may be moved into a water basin, adjust an appropriate water flow, and cool with running tap water for 10 min.
• 5.8 Remove the flasks from the water bath. Titrate the iodine liberated in the flasks respectively with c(Na2S2O3)=0.005 mol/L sodium thiosulfate standard solution until pale yellow. Then continue slowly titrating until the yellow color just disappears.

9. Qualitative and quantitative determination and calculation formula

• The peroxide value of the test sample (calculated as hydrogen peroxide) X is expressed in mg/kg and calculated according to the following formula: X = (V0 − V1) × c × 34 × 10³ / (50 × ρ)
• Where:
  • V0—— volume of sodium thiosulfate standard titration solution (5.2.2) required for titration of the test sample, mL; (requires confirmation against the source standard (source-text extraction): the correspondence between symbols and definitions in the original formula is suspected to be misaligned; the original text writes "Vo— test sample titration..." and "V,— blank titration...", but conventionally it should be V0 blank and V1 test sample, requires confirmation)
  • V1—— volume of sodium thiosulfate standard titration solution (5.2.2) required for blank titration, mL; (requires confirmation against the source standard (source-text extraction), same as above)
  • c—— concentration of sodium thiosulfate standard titration solution, mol/L;
  • ρ—— density of the test sample at sampling, g/mL. (the density unit is illegible in the source transcription and remains unverified)
• 6.2 Report the peroxide value in the test sample using mg/kg, taking the average of duplicate determination results rounded to an integer.

10. Precision

• 7.1 Repeatability: When the same operator uses the same instrument to determine the same test sample, the difference between two determination results shall not exceed the following value:
  • Peroxide value 1～? mg/kg, repeatability 6 mg/kg. (the applicable peroxide-value range is incomplete in the source transcription; verify its limits before applying the repeatability value)
• 7.2 Reproducibility: When different operators in different laboratories determine the same test sample, the difference between any two independent results shall not exceed the following value:
  • Peroxide value 1～? mg/kg, reproducibility 10 mg/kg. (requires confirmation against the source standard (source-text extraction): the original range "1~f" cannot be identified; the original reproducibility value "iO" is suspected to be 10)

11. Report

• 6.2 Report the peroxide value in the test sample using mg/kg, taking the average of duplicate determination results rounded to an integer.
• Other reporting requirements: not provided in the available source.

12. Referenced documents

• GB 11083-89 "Determination of Peroxide Value of Liquid Paraffin" (replaced)
• ASTM D2340-82 "Test Method for Peroxides in Styrene Monomer" (equivalently adopted)
• Other 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 Q&A