GB/T 508-1985 Determination of Ash in Petroleum Products

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 title / English name / replacement relationship

• Standard number: GB/T 508-85 (the cover and page-header designations are garbled in the source transcription; check the exact designation against the original standard)
• Chinese name: Determination of Ash in Petroleum Products
• English name: Petroleum products — Determination of ash
• Replacement relationship: not provided in the available source
• Other: UDC 535.37:620 .179.1; issued on 1985-04-19, implemented on 1986-04-01; confirmed in 1991; adopted by reference the international standard ISO 6245-1982 "Determination of Ash in Petroleum Products"; modified according to Amendment No. 1 of GB/T 508-85

2. Scope of application and non-applicability

• Applicable to: determination of the ash content of petroleum products.
• Not applicable to: petroleum products containing ash-forming additives (including certain phosphorus-containing compound additives); leaded lubricating oils and used engine crankcase oils.

3. Method principle

Use ashless filter paper as an ignition wick, ignite the test sample placed in a suitable container, and let it burn until only ash and residual carbon remain. The carbonaceous residue is then heated in a 775℃ high-temperature furnace to convert it into ash, then cooled and weighed.

4. Reagents and materials (purity / preparation)

• Hydrochloric acid: chemically pure, prepared as a 1:4 aqueous solution.
• Quantitative filter paper: diameter 9 centimeters.

5. Instruments and equipment

• 2.1.1 Porcelain crucible or porcelain evaporating dish: 50 milliliters and 90～120 milliliters. Note: The porcelain crucible or porcelain evaporating dish may be used until the glaze inside it is damaged.
• 2.1.2 Electric hot plate or electric furnace.
• 2.1.3 High-temperature furnace: capable of heating to a constant 775±25℃, with a temperature regulator to adjust the furnace temperature (the temperature of the high-temperature furnace may be measured with a thermocouple and a millivoltmeter graduated in 1000℃). The thermocouple is best placed in the hole in the rear wall of the furnace, with the hot junction at the center of the furnace chamber.
• 2.1.4 Desiccator: without desiccant.

6. Recommended operating conditions

• High-temperature furnace temperature: 775±25℃.
• During combustion, maintain the flame height at about 10 centimeters.
• Heating time for ashing the residue: generally maintain for 1.5～2.0 hours.
• After ignition, cool in air for 3 minutes, then transfer to a desiccator and cool to room temperature.
• Preheating temperature before sampling for viscous or waxy samples: 50～60℃.

7. Sampling and sample preparation

• 4.2 Before sampling, shake the sample in the bottle (its amount must not exceed 3/4 of the bottle volume) vigorously and uniformly to ensure that the sample taken is truly representative. For viscous or waxy samples, preheat to 50～60℃, then shake uniformly before sampling.
• 5.1 Weigh the constant-weight crucible to the nearest 0.01 grams, and weigh the sample into it with the same accuracy. The amount of sample taken depends on the ash content of the sample, limited to the amount of sample sufficient to produce 20 milligrams of ash, but at most not exceeding 100 grams. If there is a large amount of sample and one crucible cannot hold it, the sample must be burned in two portions; in this case, a suitable sample container may be used, and the amount of sample used is obtained from the difference between its initial weight and final weight.
• Note: Depending on the situation, generally 25 grams of sample may be taken and placed in a 50 milliliter crucible for the test, but when there is a dispute over the test results, the test should be carried out according to the above sample amount.

8. Analysis procedure

• 4.1 Pour dilute hydrochloric acid (1:4) into the porcelain crucible (or porcelain evaporating dish) to be used, boil for several minutes, and wash with distilled water. After drying, place it in a high-temperature furnace and calcine at 775±25℃ for at least 10 minutes, remove and cool in air for 3 minutes, then transfer to a desiccator. After cooling to room temperature, weigh to the nearest 0.0001 grams. Repeat the calcination, cooling, and weighing until the difference between two consecutive weighings is not greater than 0.0005 grams.
  • Note: It is appropriate to place a pair of crucibles in one desiccator. For a pair of 50 milliliter crucibles, cooling for generally 30～45 minutes can reach room temperature; for a pair of 100 milliliter crucibles, cooling for generally 45 minutes to 1 hours can reach room temperature. Once the crucible has cooled, it should be weighed; whatever length of time the crucible stays in the desiccator, all subsequent weighings should be carried out after allowing it to stay in the desiccator for the same length of time.
• 5.2 Fold a sheet of quantitative filter paper in two, roll it into a cone shape, use scissors to cut off the top portion 5～10 millimeters from the tip, and place it in the crucible. Stand the rolled conical filter paper (ignition wick) steadily upright in the oil in the crucible, covering most of the sample surface.
• 5.3 When determining a sample containing water, place the crucible containing the sample and ignition wick on an electric hot plate and heat slowly so that it does not splash, allowing the water to evaporate slowly until the filter paper soaked with the sample can ignite. After the ignition wick is soaked with the sample, ignite and burn. The combustion of the sample should proceed until a dry carbonized residue is obtained. During combustion, maintain the flame height at about 10 centimeters. For viscous or waxy samples, heat on an electric furnace while burning. After combustion begins, adjust the heating so that the sample does not splash and does not overflow from the edge of the crucible.
• 5.4 After the sample has burned, transfer the crucible containing the residue into a high-temperature furnace heated to 775±25℃ (care should be taken to prevent sudden deflagration and ejection. If possible, the crucible may first be transferred into the furnace, or transferred into the furnace at a lower temperature, and then raised to 775±25℃), and heat at this temperature until the residue is completely reduced to ash (generally maintain for 1.5～2.0 hours).
• 5.5 After the residue has become ash, place the crucible in air to cool for 3 minutes, then cool in a desiccator to room temperature and weigh to the nearest 0.0001 grams. Transfer again to a high-temperature furnace and calcine for 20～30 minutes. Repeat the calcination, cooling, and weighing until the difference between two consecutive weighings is not greater than 0.0005 grams.

9. Qualitative and quantitative determination and calculation formula

The ash content X (%) of the sample is calculated according to the following formula:

X = G / W × 100

Where:

• G — weight of ash
• W — weight of sample

(The original formula source-text extraction is unclear; the symbols have been restored from context and conventional expression, requires confirmation against the source standard (source-text extraction))

10. Precision

Use the following values to judge the reliability of the results (95% confidence level).

7.1 Repeatability: the difference between two results measured by the same operator shall not exceed the following values:

7.2 Reproducibility: the difference between two results provided by two laboratories shall not exceed the following values:

11. Report

Take the arithmetic mean of two repeat determination results as the ash content of the sample.

12. Referenced documents

• ISO 6245-1982 "Determination of Ash in Petroleum Products" (adopted by reference)
• GB/T 508-85 Amendment No. 1

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 reference