SH/T 0243-1992 Determination of Iodine Value of Solvent Gasoline

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Card type: Test method

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

• Standard number: SH/T 0243-92 (confirmed in 2004)
• Chinese name: Determination of Iodine Value of Solvent Gasoline
• English name: not provided in the available source
• Replacement relationship: replaces SY 2301-82
• First issued: 1954
• Technical administration unit: Petroleum and Chemical Research Institute
• Drafting unit: Shanghai Gaoqiao Petrochemical Company Refinery responsible for drafting
• 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 method for determining the iodine value of a sample.
• This standard applies to solvent gasoline.
• Not applicable: not provided in the available source.

3. Method principle

In an iodine flask, inject 10mL chloroform, and accurately inject a sample of known density as specified, then add dropwise 5mL of Hubel-Waller solution, stopper the flask, carefully shake the mixture in the flask, wait until the mixture is completely transparent, place the flask in a dark place for 1h, then add to the flask 100g/L potassium iodide solution 10mL and distilled water 200mL. Under constant shaking, titrate with sodium thiosulfate standard titration solution [c(Na₂S₂O₃)=0.1mol/L], when the mixture turns yellow, add freshly prepared 5g/L starch solution 2mL, until the blue color disappears. Determine a blank sample by the same procedure. Calculate the iodine value of the sample from the volume of sodium thiosulfate standard titration solution consumed.

Definition: The number of grams of iodine that can be absorbed by 100g of sample is called the iodine value. The iodine value is used to identify the degree of unsaturation of gasoline.

4. Reagents and materials (purity / preparation)

• 5.1 hydrochloric acid: chemically pure.
• 5.2 95% ethanol: analytically pure.
• 5.3 chloroform: chemically pure; after shaking with potassium iodide solution it must be colorless.
• 5.4 iodine: analytically pure.
• 5.5 potassium iodide: chemically pure, prepared as 100g/L solution.
• 5.6 mercuric chloride (corrosive sublimate): chemically pure.
• 5.7 sodium thiosulfate: analytically pure, prepared as c(Na₂S₂O₃)=0.1mol/L standard titration solution.
• 5.8 starch: freshly prepared 5g/L starch solution.

Preparation work (preparation of Hubel-Waller solution): Dissolve 25g iodine in 500mL 95% ethanol; separately dissolve 30g mercuric chloride (corrosive sublimate) in 500mL distilled 95% ethanol; these two portions of solution must be filtered before mixing together, then add 50mL hydrochloric acid. The Hubel-Waller solution can be stored in the dark for 15d.

Standardization of sodium thiosulfate standard titration solution (Note): Take an accurately weighed mass of sublimed pure iodine and dissolve it in potassium iodide solution, use starch solution as indicator, titrate with sodium thiosulfate standard titration solution (5.7 clause) until the blue-purple color disappears. In addition, the sodium thiosulfate standard titration solution can also be standardized with potassium dichromate reference solution.

5. Apparatus and equipment

• 4.1 iodine flask: 500mL.
• 4.2 graduated cylinder: 25, 50mL.
• 4.3 burette: specification not provided in the available source (source-text extraction doubtful point, requires confirmation against the source standard (source-text extraction)).
• 4.4 pipette: 10, 25mL.
• See also main text: pipette 20mL (original listed after 4.4, source-text extraction typesetting doubtful point, requires confirmation against the source standard (source-text extraction)).

6. Recommended operating conditions

• Time in dark place: 1h.
• Concentration of sodium thiosulfate standard titration solution for titration: c(Na₂S₂O₃)=0.1mol/L.
• Indicator: freshly prepared 5g/L starch solution 2mL, added when the mixture turns yellow.
• Amount of Hubel-Waller solution: 5mL; when determining iodine value of 0.5～2.0g/100g, use 20mL.
• Sample amount: generally 20mL; when iodine value is 2.0～5.0g/100g, measure 10mL.
• Amount of chloroform: 10mL.
• Amount of potassium iodide solution (100g/L): 10mL; if red mercuric iodide precipitate separates out, add more until the precipitate disappears, and add the same amount to the blank at the same time.
• Distilled water: 200mL.

7. Sampling and sample preparation

• Sample density is determined according to GB/T 1884 and GB/T 1885.
• Use a pipette to inject the sample whose density has been determined according to GB/T 1884 and GB/T 1885, 20mL; when the iodine value is 2.0～5.0g/100g, measure the sample whose density has been determined according to GB/T 1884 and GB/T 1885, 10mL.
• Other sampling and preparation details: not provided in the available source.

8. Analytical procedure

7.1 In an iodine flask, inject chloroform 10mL, then use a pipette to inject the sample whose density has been determined according to GB/T 1884 and GB/T 1885, 20mL. When the iodine value is 2.0～5.0g/100g, measure the sample whose density has been determined according to GB/T 1884 and GB/T 1885, 10mL. Use a burette to add dropwise 5mL Hubel-Waller solution to the mixture of sample and chloroform (when determining iodine value of 0.5～2.0g/100g, use 20mL Hubel-Waller solution); this solution should be added slowly drop by drop, and the rate of addition must be completely uniform. Stopper the iodine flask tightly with a ground-glass stopper. To avoid loss of iodine by volatilization, this ground-glass stopper should be pre-moistened with 100g/L potassium iodide solution. After stoppering, carefully shake the mixture in the flask. After shaking, the mixture must be completely transparent; otherwise, a small amount of chloroform must be added to the mixture.

7.2 In order to determine the iodine content of the Hubel-Waller solution, a blank sample containing no sample must be prepared at the same time, in which only chloroform 10mL and the same volume of Hubel-Waller solution as used in the determination are used; when adding chloroform to the iodine flask containing the sample, the same amount of chloroform must also be added to the iodine flask of the blank sample.

7.3 Place the iodine flasks containing the mixture according to clauses 7.1 and 7.2 in a dark place for 1h. After standing for 1h, add to each iodine flask 100g/L potassium iodide solution 10mL and distilled water 200mL, and at the same time carefully rinse the stopper and neck of the flask with distilled water. After adding the potassium iodide solution, if a red mercuric iodide precipitate separates out from the mixture of the sample, it is necessary to add more 100g/L potassium iodide solution until the precipitate disappears; at the same time, add the same amount of 100g/L potassium iodide solution to the iodine flask of the blank sample. The mixture should be titrated with sodium thiosulfate standard titration solution (5.7 clause) under constant shaking. When the mixture appears yellow, add freshly prepared 5g/L starch solution 2mL, and continue titrating with sodium thiosulfate standard titration solution (5.7 clause) until the blue-purple color disappears. The mixture of the blank sample is also titrated by the same method.

9. Qualitative and quantitative determination and calculation formula

The iodine value of the sample X (g/100g) is calculated according to the following formula:

X = (V₁ − V₂) × c × 0.127 × 100 / (V₃ × ρ)

Where:

• V₁ — volume of sodium thiosulfate standard titration solution (5.7 clause) consumed in titrating the mixture of the blank sample, mL;
• V₂ — volume of sodium thiosulfate standard titration solution (5.7 clause) consumed in titrating the mixture of the sample, mL;
• c — actual concentration of sodium thiosulfate standard titration solution (5.7 clause), mol/L;
• 0.127 — mass of iodine in grams equivalent to 1.00mL sodium thiosulfate standard titration solution [c(Na₂S₂O₃)=1.000mol/L];
• V₃ — volume of the sample, mL;
• ρ — density of the sample at the time of testing, g/mL.

(Note: In the original source-text extraction, the symbols V₁ and V₂ are noisy; according to context and formula logic they correspond to the volumes consumed by the blank and the sample; requires confirmation against the source standard (source-text extraction).)

10. Precision

Repeatability: the difference between two results of repeated determinations by the same operator shall not be greater than 15% of the smaller result.

11. Report

Take the arithmetic mean of two results of repeated determinations as the iodine value of the sample.

12. Referenced documents

• GB/T 1884 Standard test method for density of crude petroleum and liquid petroleum products (hydrometer method)
• GB/T 1885 Petroleum measurement tables

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