GB/T 505-1965 Determination of mercaptan sulfur in engine fuels (ammonia-copper sulfate method)

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Card type: Test method

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

• Standard number: GB 505-65 (the original cover is marked "GB 505-05", the text page header is marked "GB 505-65", the file name is inferred to be GBT-505-1965, the standard number writing requires confirmation against the source standard (source-text extraction))
• Chinese name: Determination of mercaptan sulfur in engine fuels (ammonia-copper sulfate method)
• English name: Engine fuels-Determination of mercaptan sulphur-Ammonia-cupric sulfide method (the original source-text extraction is "Determ ination" "Am monia", restored according to semantics, requires confirmation against the source standard (source-text extraction))
• Replacement relationship: From the date of implementation of this standard, the former Ministry of Petroleum standard SYB 2120-59 "Determination of mercaptan sulfur in engine fuels" is invalid (the original source-text extraction is "[garbled invalidation wording]", requires confirmation against the source standard (source-text extraction))
• Confirmation status: confirmed in 1982
• Issued/implemented: issued by the National Science Commission Standards Bureau in 1965-01-20, implemented in 1965-10-01

2. Scope of application and non-applicability

• Applicable to the determination of the content of mercaptan sulfur in engine fuels.
• Not applicable: no explicit non-applicability clause is provided in the available source.
• Note (note to clause 4.4): The sample should not contain hydrogen sulfide; if it contains hydrogen sulfide, it can be removed by treatment with acidified 10% cadmium chloride solution.

3. Method principle

The ammonia-copper sulfate solution interacts with mercaptans in the fuel to form copper mercaptide compounds. (original "1 Method summary")

4. Reagents and materials (purity / preparation)

• 3.1 Copper sulfate: chemically pure
• 3.2 Ammonia water: chemically pure
• 3.3 Potassium iodide: chemically pure
• 3.4 Sulfuric acid: chemically pure
• 3.5 Sodium thiosulfate: analytically pure, prepared as a 0.1N aqueous solution
• 3.6 Freshly prepared 0.5% starch aqueous solution

Preparation:

• 4.1 Preparation of ammonia-copper sulfate solution: Dissolve copper sulfate in 50–70°C distilled water to saturation, filter the solution into a porcelain evaporating dish, allow to stand and cool to room temperature (20±5°C), filter off the precipitated crystals, and dry them with filter paper until the crystals do not stick to a glass rod when stirred. Weigh 3.9 grams of recrystallized copper sulfate (weighed to 0.01 grams), place in a 1 liter volumetric flask, dissolve with 700 milliliters of distilled water, slowly add ammonia water with a graduated cylinder until the basic copper salt precipitate is completely dissolved, then add 50–100 milliliters of ammonia water to the transparent solution, and add distilled water to make 1 liters. The solution must be dark blue and completely transparent.
• 4.2 Titration titer calibration: Take 100 milliliters of the solution, add sulfuric acid dropwise until the ammonia is completely neutralized (the solution appears light blue), then add an excess of 1~2 milliliters of sulfuric acid, cool to room temperature (20±5°C), add 3 grams of potassium iodide (weighed to 0.01 grams), titrate with 0.1N sodium thiosulfate solution, and when the solution becomes slightly yellow, add a few drops of freshly prepared 0.5% starch solution, and continue titrating until the blue color disappears.
• Preparation of starch solution: Take 0.5 grams of soluble starch, grind it into powder, mix it well with a small amount of cold water, slowly add it to 100 milliliters of boiling distilled water, continue boiling for 1~2 minutes until almost completely transparent, then filter.
• 4.4 Sample pretreatment: When determining mercaptan sulfur in fuels and cracked products containing wood tar antioxidants or p-hydroxybiphenyl, the sample is pretreated twice with 10% ammonia water equal to 20% of its volume, then washed twice with distilled water and filtered.
• 4.4 Note: If the sample contains hydrogen sulfide, treat it several times with acidified 10% cadmium chloride solution (add 1 milliliters of hydrochloric acid to 100 milliliters of solution) until hydrogen sulfide is completely removed; each time a portion of fresh cadmium chloride solution is used for treatment, the sample must be filtered to remove the precipitate until the sample remains transparent when contacted with a portion of fresh cadmium chloride.

5. Apparatus and equipment

• 2.1 Volumetric flask: 1000 milliliters
• 2.2 Graduated cylinder: 25 and 100 milliliters
• 2.3 Burette: 25 milliliters
• 2.4 Pipette: 100 milliliters
• 2.5 Flat-bottomed flask: 250 milliliters
• 2.6 Porcelain evaporating dish: about 100 and 250 milliliters (the original source-text extraction is "[garbled evaporating-dish name]", requires confirmation against the source standard (source-text extraction))
• 2.7 Separatory funnel: 150, 200 or 250 milliliters
• 2.8 Beaker: 100 and 250 milliliters
• 2.9 Conical flask: 250 milliliters
• 2.10 Glass funnel (the original source-text extraction is "[garbled glass-funnel name]", requires confirmation against the source standard (source-text extraction))
• 2.11 Mercury thermometer: 0~100°C, graduation 1°C

6. Recommended operating conditions

• Titration temperature: room temperature (20±5°C) (see 4.2)
• Solution preparation temperature: 50~70°C (see 4.1)
• Determination of titration endpoint: the light blue color of the aqueous layer does not disappear after vigorous shaking for 5 minutes, and it is considered that the endpoint has been reached (see 5)
• Other operating conditions are not provided in the available source.

7. Sampling and sample preparation

• Determine the sampling amount according to the predicted content of mercaptan sulfur in the sample:
  • When the mercaptan sulfur content is below 0.01%, take 100 milliliters
  • When it is 0.01~0.02%, take 50 milliliters
  • When it is above 0.02%, take 25 milliliters
• For sample pretreatment, see 4.4 (fuels and cracked products containing wood tar antioxidants or p-hydroxybiphenyl; samples containing hydrogen sulfide).

8. Analytical procedure

• Inject the sample into a separatory funnel and titrate with ammonia-copper sulfate solution.
• At the beginning of titration, add the ammonia-copper sulfate solution 1 milliliters at a time, then add 0.5 milliliters at a time, and finally add 3 drops or 4 drops at a time.
• When determining samples with low mercaptan content, the ammonia-copper sulfate solution may be added 0.2 milliliters at a time using a microburette.
• After each addition of ammonia-copper sulfate solution, shake the separatory funnel containing the sample vigorously until the light blue color of the aqueous layer disappears.
• To make the endpoint clearer, whenever the volume of the colorless aqueous layer reaches 4~5 milliliters, draw it off from the bottom.
• If the light blue color of the aqueous layer does not disappear after vigorous shaking for 5 minutes, the titration endpoint is considered to have been reached.
• If the color of the aqueous layer is difficult to judge in the separatory funnel, draw 2~3 drops of the solution from the separatory funnel into a white porcelain evaporating dish and observe the light blue color against a white background.

9. Qualitative and quantitative determination and calculation formulas

• 4.3 Calculation formula for the titer T of the ammonia-copper sulfate solution (1):

  T = (V · T₁ × 32.06 × 2) / (126.91 × 100)

  Where:

  • V—— the volume of 0.1N sodium thiosulfate solution consumed in titrating the ammonia-copper sulfate solution, milliliters
  • T₁——the titer of the 0.1N sodium thiosulfate solution, expressed as grams of iodine equivalent per milliliter of solution
  • 32.06—— atomic weight of sulfur
  • 126.91—— atomic weight of iodine

  The titer of the ammonia-copper sulfate solution prepared according to clause 4.2 shall be calibrated at least once a month.

  Note: The titer of the sodium thiosulfate solution is expressed as grams of iodine equivalent per milliliter of solution. Determination method: accurately weigh analytically pure iodine, use starch solution as indicator, and titrate with 0.1N sodium thiosulfate solution. Divide the grams of iodine by the milliliters of 0.1N sodium thiosulfate solution consumed in the titration to obtain the titer.

• 6 Calculation: The weight percentage X of mercaptan sulfur content in the sample (%) is calculated according to formula (2):

  X = (V₁ · T) / (V₂ · ρ) (the original source-text extraction formula is incomplete, requires confirmation against the source standard (source-text extraction))

  Where:

  • V₁——the volume of ammonia-copper sulfate solution consumed in titrating the sample, milliliters
  • T—— the titer of the ammonia-copper sulfate solution, expressed as grams of mercaptan sulfur equivalent per milliliter of solution
  • V₂——the volume of the sample, milliliters
  • ρ—— the density of the sample at the test temperature, grams/milliliter

10. Precision

• The difference between two repeated determination results shall not exceed 0.0005%. (the original clause number source-text extraction is "1 Precision", the number requires confirmation against the source standard (source-text extraction))

11. Report

• 8.1 Take the arithmetic mean of two repeated determination results as the test result.
• 8.2 When the mercaptan sulfur content in the sample is below 0.0005%, it is considered absent. (the original source-text extraction is "[garbled analyte-content wording]", restored according to semantics, requires confirmation against the source standard (source-text extraction))

12. Referenced documents

• No list of normative referenced documents is provided in the available source.
• Additional notes: This standard was proposed by the Ministry of Petroleum Industry of the People's Republic of China; drafted by the Petroleum Science Research Institute of the Ministry of Petroleum Industry (the original source-text extraction is "[garbled research-institute name]", requires confirmation against the source standard (source-text extraction)); from the date of implementation of this standard, the former Ministry of Petroleum standard SYB 2120-59 "Determination of mercaptan sulfur in engine fuels" is invalid.

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