GB/T 1794-1979 Determination of anti-icing additive content in jet fuel

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Card type: Test method

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

• Standard number: GB 1794-79 (confirmed in 1988)
• Chinese name: Determination of anti-icing additive content in jet fuel
• English name: Jet fuels-Determinatlon of Icing Inhibitor content (original text as such, Determination suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction))
• Method number: This standard includes three methods—Method A (iodometric method), Method B (freezing point method), Method C (refractometric method)
• Replacement relationship: not provided in the available source

2. Scope of application and non-applicability

• Applicable to the determination of anti-icing additive content in jet fuel.
• Includes three methods, all of which can be used to determine the content of four anti-icing additives: full-range ethylene glycol methyl ether (T1301), full-range ethylene glycol ethyl ether (T1302), ethylene glycol monomethyl ether (T1303), ethylene glycol monoethyl ether (T1304).
• Determination range is 0.05~0.25% (volume).
• Method A has higher precision, but the procedure is more complex, and it is suitable for factory laboratory determination and arbitration testing. Method B and Method C are simple and rapid, and are suitable for field determination.
• Not applicable: not provided in the available source (Method A 5.1 clause states: if the volume of 0.1N sodium thiosulfate standard solution consumed by titration is less than 5.0 milliliters, then this method cannot be applied).

3. Method principle

• General principle: During determination, the anti-icing additive in the fuel is first extracted with water, and then Method A uses the iodometric method for determination, Method B uses the freezing point method for determination, and Method C uses the refractive index method for determination.
• Method A (iodometric method) method summary: first extract the anti-icing additive in the fuel with water, then determine by the iodometric method.
• Method B (freezing point method) method summary: first extract the anti-icing additive in the fuel with water, then determine by the freezing point method.
• Method C (refractometric method) method summary: first extract the anti-icing additive in the fuel with water, then determine by the refractive index method.

4. Reagents and materials (purity / preparation)

Method A

• 3.1 Anti-icing additive standard solution: place 10.00 milliliters of anti-icing additive into a 1 liter volumetric flask, dilute to the mark with distilled water, mix thoroughly, and prepare an anti-icing additive standard solution of 1% concentration (volume). Then pipette 10.00 milliliters of the 1% concentration anti-icing additive standard solution into a 100 milliliter volumetric flask, dilute to the mark with distilled water, mix thoroughly, and prepare an anti-icing additive standard solution of 0.1% concentration (volume).
• 3.2 0.2000N Potassium dichromate standard solution: accurately weigh 4.9035 grams of analytically pure potassium dichromate dried at 120℃ to constant weight, dissolve with a small amount of water, and transfer to a 500 milliliter volumetric flask. Dilute to the mark with water and mix thoroughly.
• 3.3 0.1N Sodium thiosulfate standard solution: weigh 25±0.1 grams of analytically pure sodium thiosulfate containing 5 grams of water of crystallization, dissolve in 1000 milliliters of water, add 0.01 grams of sodium carbonate to stabilize the solution, and mix thoroughly. Allow to stand for 24 hours before standardization. This solution should be standardized once every two weeks.
  • Standardization method: use a pipette to transfer 10 milliliters of 0.2000N potassium dichromate standard solution into a 500 milliliter iodine flask, slowly add 5 milliliters of sulfuric acid from a burette, then add 50 milliliters of water and cool to room temperature. Then add about 3 grams of potassium iodide and mix thoroughly. Titrate with sodium thiosulfate solution while shaking continuously until the color changes from brown to yellow-green. Add 2 milliliters of starch indicator and continue titrating until the color rapidly changes from light blue to blue-green. When approaching the endpoint, carefully swirl the iodine flask, and after each addition of 1 drops of sodium thiosulfate solution, shake vigorously. The normality N of the sodium thiosulfate standard solution is calculated according to formula (1) (the original formula source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction)).
• 3.4 Starch indicator: mix 4 grams of soluble starch, 10 milligrams of mercuric iodide (preservative), and 10 milliliters of water, slowly add this suspension to 1 liters of boiling water, boil for 5 minutes, cool, and store in a stoppered glass bottle.
• 3.5 Crystalline potassium iodide.
• 3.6 Sulfuric acid: analytically pure.
• 2.2 Material: crushed ice.

Method B

• 11 Reagent: anti-icing additive.
• 10.2 Materials: crushed ice; table salt.

Method C

• 18 Reagent: anti-icing additive.

5. Instruments and equipment

Method A (2.1 instruments)

• 2.1.1 Conical flask: 50 milliliters.
• 2.1.2 Electric heating plate.
• 2.1.3 Iodine flask: 500 milliliters.
• 2.1.4 Separatory funnel: pear-shaped with standard ground joint, 125 milliliters.
• 2.1.5 Hard glass tube: 22×175 millimeters, with stand.
• 2.1.6 Burette: 25 and 50 milliliters.
• 2.1.7 Pipettes: 5, 10 and 25 milliliters.
• 2.1.8 Volumetric flasks: 100, 500 and 1000 milliliters.
• 2.1.9 Stoppered glass bottle.

Method B (10.1 instruments)

• 10.1.1 Separatory funnel: with standard ground joint, 1000 milliliters, with stand.
• 10.1.2 Pipette: 10 milliliters.
• 10.1.3 Graduated cylinder: 1000 milliliters.
• 10.1.4 Test tube: φ20×175 millimeters.
• 10.1.5 Thermometer: graduation 0.1℃.
• 10.1.6 Metal ring stirrer.
• 10.1.7 Ice-salt bath (crushed ice:table salt = 3:1), or other cooling baths from -10℃ to -15℃.
• 10.1.8 Magnifying glass.

Method C (17 instruments)

• 17.1 Refractometer: Abbe type.
• 17.2 Separatory funnel: 500 milliliters.
• 17.3 Graduated cylinder: 500 milliliters.
• 17.4 Pipette: 5 milliliters.
• 17.5 Dropper.

6. Recommended operating conditions

• Method A: cool in ice bath; keep in boiling water bath for 10 minutes; when titration approaches the endpoint, carefully swirl the iodine flask, and after each addition of 1 drops, shake vigorously.
• Method B: cooling bath temperature -10℃ to -15℃; the thermometer mercury bulb is located in the middle of the water; the thermometer must be calibrated, and the mercury bulb must be completely immersed in the extract; with the aid of a magnifying glass, 0.02℃ can be read.
• Method C: the refractive index is taken as the arithmetic mean of four readings.
• Others: not provided in the available source.

7. Sampling and sample preparation

• Method A 5.1: pipette 25.0 milliliters of sample into a dry 125 milliliter separatory funnel, and use a pipette to add 25.0 milliliters of water, stopper the funnel and shake vigorously for 2 minutes, allow the two phases to separate, put the aqueous phase into a 50 milliliter conical flask, and take 5.00 milliliters of this solution into a φ22×175 millimeter test tube.
• Method A 5.2 Blank: take a sample without anti-icing additive and carry out the blank determination according to 5.1. If such a sample is not available, a sample with anti-icing additive may also be used instead. In this case, use an equal volume of water to extract the anti-icing additive from the sample that already contains anti-icing additive. During extraction, shake vigorously for 5 minutes to remove water. Repeat the water extraction once more. After two water-wash extractions, the anti-icing additive contained in the sample can be completely removed.
• Method B 12.1: measure 800 milliliters of sample with a graduated cylinder and pour into a separatory funnel. Use a pipette to add 10 milliliters of distilled water (or tap water), stopper with a glass stopper, shake vigorously for 5 minutes, and let stand until completely separated (2~3 minutes). Note: vigorous shaking is the key to test repeatability. Shaking for 5 minutes can completely extract the extractable portion determined by the distribution law.
• Method C 19.2: measure 300 milliliters of sample with a graduated cylinder and pour into a separatory funnel. Use a pipette to add 5 milliliters of distilled water, stopper with a glass stopper, shake vigorously for 5 minutes, and let stand until completely separated.
• Standard sample preparation (Method C 19.1): respectively dilute 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 milliliters of anti-icing additive with jet fuel containing no anti-icing additive to 2000 milliliters, to prepare standard samples with anti-icing additive contents of 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30% (volume) (the original text "0.26%" is suspected to be source-text extraction noise of 0.20%, requires confirmation against the source standard (source-text extraction)). Shake well. Note: if the percentage content (weight) needs to be determined, the anti-icing additive content of the standard sample should also be prepared according to weight percentage.

8. Analysis steps

Method A

• 4 Preparation—determination of factor F: define factor F as the number of milliliters of anti-icing additive equivalent to each milliliter of 1 equivalent potassium dichromate. Pipette 5.00 milliliters of anti-icing additive standard solution into a φ22×175 millimeter test tube, use a pipette to add 10.00 milliliters of 0.2000N potassium dichromate standard solution, and place the test tube in an ice bath. After the solution is completely cooled, add 5 milliliters of sulfuric acid from a burette. Shake the test tube in the ice bath continuously. Mix the acid and aqueous phase thoroughly without overheating. After the solution is cooled, place the test tube in a boiling water bath for 10 minutes, then place the test tube in an ice bath and cool it to room temperature or lower. Transfer the liquid in the test tube to a 500 milliliter iodine flask, wash the test tube four times with water, using 5 milliliters of water each time, and add the washings to the iodine flask. Add about 3 grams of potassium iodide, and titrate with 0.1N sodium thiosulfate standard solution to the endpoint as specified in 3.3. When approaching the endpoint, carefully swirl the iodine flask. After each addition of 1 drops of 0.1N sodium thiosulfate standard solution, shake vigorously. The determination of factor F should be carried out three times, and the average value calculated. The difference between any one of the three measured values and the average value is not greater than 0.0001.
• 5.1 Analysis of the test sample: take 5.00 milliliters of the water extract in a test tube, add 0.2000N of potassium dichromate standard solution 10.00 milliliters using a burette or pipette, and place the test tube in an ice bath. After the solution has cooled, add 5.00 milliliters of sulfuric acid using a burette while continuously shaking the test tube in the ice bath. Mix the acid and aqueous phase thoroughly without overheating. After the solution has cooled, place the test tube in a boiling water bath for 10 minutes, then cool the solution in an ice bath to room temperature. Then transfer the solution to a 500 milliliter iodine flask, add about 3 grams of potassium iodide, and titrate with 0.1N sodium thiosulfate standard solution to the endpoint. When approaching the endpoint, the iodine flask should be shaken carefully, and after each addition of 1 drops of 0.1N sodium thiosulfate standard solution, it must be shaken vigorously.
• 5.2 Blank determination: see Section 7.

Method B

• 12.2: Place the aqueous layer from the separatory funnel into a test tube, insert the stopper, thermometer, and stirring loop so that the thermometer bulb is exactly in the middle of the water. Immerse the test tube in a cold bath at -10℃ to -15℃. Stir the water continuously so that temperature changes can be observed.
• 12.3: Watch the temperature change closely. When the temperature drops to a minimum, then rises rapidly and remains constant for a period (a few seconds), then falls again. Accurately read the highest temperature reached after the rapid rise (with a magnifying glass, it can be read to 0.02℃), and record it as the freezing point.
• 12.4: Referring to Method C 19.1, prepare standard samples of different concentrations using jet fuel with anti-icing additive and without anti-icing additive. According to Method C 19.2 to Chapter 20, determine the freezing point of the water extract of the standard samples, and plot the anti-icing additive content versus water extract freezing point curve.

Method C

• 19.1: Prepare standard samples and plot the anti-icing additive content versus water extract refractive index curve (see Section 7).
• 19.3: Place the aqueous layer from the separatory funnel into a test tube, use a dropper to transfer this test solution onto an Abbe refractometer, and measure its refractive index. The refractive index is taken as the arithmetic mean of four readings.

9. Qualitative and Quantitative Determination and Calculation Formulas

Method A

• Factor F is calculated according to formula (2) (the original formula source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction)): F = 0.005 / (V₁·N₁) × ... = 2.00 − V₂·N₂ (as in the original, symbols and derivation require confirmation against the source standard (source-text extraction)) Where: 0.005—— volume of anti-icing additive in the standard solution being analyzed, milliliters; —— volume of potassium dichromate standard solution, milliliters; N₁ —— normality of potassium dichromate standard solution, N; V₂ —— volume of sodium thiosulfate standard solution consumed during titration, milliliters; N₂ —— normality of sodium thiosulfate standard solution, N.
• 6.1 Anti-icing additive content in the test sample X [% (volume)] is calculated according to the following formula: X = 100F (V₀·N₁ − V₂·N₂) / (A·S) Where: F—— factor value determined by formula (2); V₀ —— volume of potassium dichromate standard solution, milliliters; N₁ —— normality of potassium dichromate standard solution, N; V₂ —— volume of sodium thiosulfate standard solution consumed during titration, milliliters; N₂ —— normality of sodium thiosulfate standard solution, N; A—— number of portions of water extract used (here A is 1/5); S—— volume of test sample, milliliters.
• In this method, the formula can also be accurately simplified to: X = 20F [2.000 − (V₂·N₂)] (4)
• 6.2 Calculate the blank value of the test sample.
• 6.3 Subtract the blank value from the value obtained in clause 6.1; this gives the volume percentage of anti-icing additive actually contained in the test sample.

Method B

• 13 Calculation: From the working curve of water extract freezing point versus anti-icing additive content, find the anti-icing additive percentage value corresponding to the freezing point of the test sample water extract; this value is the anti-icing additive content in the test sample.

Method C

• 20 Calculation: From the working curve of anti-icing additive content versus water extract refractive index, find the anti-icing additive percentage value corresponding to the refractive index of the test sample water extract; this value is the anti-icing additive content in the test sample.

10. Precision

• Method A (7): Within the range of 0.05~0.25% (volume) anti-icing additive, the difference between two repeated determination results shall not be greater than 0.005%.
• Method B (14): The difference between two repeated determination results shall not be greater than 0.01%.
• Method C (21): The difference between two repeated determination results shall not be greater than 0.01%.

11. Report

• Method A (8): Take the arithmetic mean of two repeated determination results as the anti-icing additive content in the test sample.
• Method B (15): Take the arithmetic mean of two repeated determination results as the anti-icing additive content in the test sample.
• Method C (22): Take the arithmetic mean of two repeated determination results as the anti-icing additive content in the test sample.

12. Reference Documents

• Not provided in the available source (the main text does not list a normative reference document list).

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