SH/T 0125-1992 Liquefied petroleum gas hydrogen sulfide test method (lead acetate method)

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Card type: Test method

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

• Standard number: SH/T 0125-92 (file name given as SHT-0125-1992)
• Chinese title: Liquefied petroleum gas hydrogen sulfide test method (lead acetate method)
• English title: not provided in the available source (only the equivalently adopted international standard title is given: ISO 8819—1987 "Liquefied petroleum gas hydrogen sulfide test method (lead acetate method)")
• Replacement relationship: From the date of implementation of this standard, the former national standard GB 11125-89 "Liquefied petroleum gas hydrogen sulfide test method (lead acetate method)" is void.
• Adoption relationship: This standard equivalently adopts the international standard ISO 8819—1987.
• Approval/implementation: approved by China Petrochemical Corporation 1992-05-20, implemented on 1992-05-20.
• Technical administration/drafting: technical administration by the Research Institute of Petroleum Processing; drafting by the Refining Research Institute of Luoyang Petrochemical Engineering Company; main drafter Zhang Shuhui.

2. Scope of application and non-applicability

• Applicable to the detection of hydrogen sulfide in liquefied petroleum gas.
• The lower detection limit for hydrogen sulfide is 4 mg/m³ (the source text gives "4mg/m’", requires confirmation against the source standard (source-text extraction)).
• The method is a qualitative determination of the presence or absence of hydrogen sulfide.
• Interference note: If methyl mercaptan is present, it produces a transient yellow stain on the lead acetate test strip, but it completely disappears before 5 min; other sulfides in liquefied petroleum gas do not interfere with this test.
• Note (source note): Liquefied petroleum gas and its combustion products should not severely corrode the materials they contact, nor should they react violently with them; therefore, detecting the presence of hydrogen sulfide is important; in certain applications of liquefied petroleum gas (for example, lighter fuel), the odor of hydrogen sulfide is also difficult to accept.

3. Method principle

Under specified conditions, the vaporized sample is passed through a moistened lead acetate test strip; hydrogen sulfide reacts with lead acetate to form lead sulfide (the source text gives "lead sulfide error", requires confirmation against the source standard (source-text extraction)), thereby causing the test strip to change color; the degree of color change goes from yellow to black as the amount of hydrogen sulfide present increases.

4. Reagents and materials (purity / preparation)

• Lead acetate: analytical reagent grade (content not less than 99.0%). Adoption note: domestic analytical reagent grade lead acetate is used.
• Preparation of lead acetate test strip: soak a smooth filter paper strip in 50 g/L lead acetate solution, then remove the filter paper strip and use clean filter paper to remove the excess lead acetate solution on it.
• Test strip specifications: length 51 mm, width 9.5 mm, with a circular hole of diameter 3.5 mm near the middle of one end; this hole allows the test strip to hang freely in the test apparatus.
• Test strip material: quantitative filter paper cut into small strips.
• Lead acetate test strips purchased on the market may also be used, provided that the same results as the lead acetate test strips prepared by the above method can be obtained.
• Test water: distilled water (used to moisten the test strip, see 7.3).

5. Apparatus and equipment

• Apparatus for detecting hydrogen sulfide in liquefied petroleum gas: as shown in the figure (the source text says "as shown in the figure"; the figure number requires confirmation against the source standard (source-text extraction)).
• Flowmeter: either a wet test meter or a rotameter may be used, with a flow range of 2~3 L/min.
• Apparatus figure components (source figure captions): 1— water bath; 2— stainless steel tube; 3—60~80℃ water; 4— needle valve; 5— silicone rubber tube; 6— specially made ground-glass stopper; 7— glass watch glass; 8— lead acetate test strip; 9— glass cylinder; 10— glass hook; 11— rubber stopper; 12— stainless steel sampler.
• Note: It is best to connect directly to the sample source instead of the sampler (see Chapter 6).
• Adoption note: change the rubber stopper below the glass cylinder to a ground-glass joint.

6. Recommended operating conditions

• Water temperature: 60–80℃ (pour hot water into the water bath so that the water temperature is maintained at 60–80℃).
• Gas flow rate: 2.3±0.2 L/min (adjust the needle valve).
• Exposure time: exactly 2 min.
• Test strip position: hang it on the hook in the glass cylinder so that it is exactly midway between the glass watch glass and the bottom end of the stopper above.
• Flushing: flush the pipeline and apparatus for about 1 min.
• Note: Any blockage of the flowmeter connected downstream of the test apparatus or rapid operation of the needle valve will create overpressure in the glass cylinder.

7. Sampling and sample preparation

• Because of the chemical activity and physical adsorption properties of hydrogen sulfide, it is highly desirable to connect the test apparatus directly to the sample source and test on site, rather than transferring the sample to a sampler and taking it back to the laboratory for testing.
• Experience has shown that even in liquefied petroleum gas samples collected with a thoroughly cleaned stainless steel sampler, the hydrogen sulfide concentration will decrease; conversely, it has been found that when a liquefied petroleum gas sample containing no hydrogen sulfide is transferred to a sampler that has not been strictly cleaned or has been used to collect samples containing hydrogen sulfide, the hydrogen sulfide concentration will increase. This indicates that hydrogen sulfide content data measured in the laboratory are unreliable.
• The test specimen is vaporized liquefied petroleum gas (see Chapter 1, Chapter 2).

8. Analytical procedure

• 7.1 Connect the apparatus described in 3.1.1 to the sample source using the shortest possible clean stainless steel tube. Note: Because hydrogen sulfide has an affinity for rubber, rubber hoses, rubber stoppers, and the like should be avoided to prevent erroneous results.
• 7.2 Flush the pipeline and apparatus for about 1 min, pour hot water into the water bath so that the water temperature is maintained at 60~80℃, and adjust the needle valve so that the gas flow rate is 2.3±0.2 L/min.
• 7.3 Immediately hang a lead acetate test strip moistened with distilled water on the hook in the glass cylinder described in 3.1.1 so that it is exactly midway between the glass watch glass and the bottom end of the stopper above, let the test strip be exposed to the sample gas stream of 2.3±0.2 L/min for exactly 2 min, remove the test strip, and judge as described in Chapter 8.

9. Qualitative and quantitative determination and calculation formula

• Qualitative determination (Chapter 8):
  • Compare the test strip exposed to the sample with a moistened test strip not exposed to the sample.
  • 8.1 If there is no obvious color difference, judge that there is no hydrogen sulfide in the sample.
  • 8.2 If there is an obvious color difference, wait for 5 min, then compare the test strip exposed to the sample with a moistened test strip not exposed to the sample.
    • a. If the test strip exposed to the sample retains an obvious color, judge that hydrogen sulfide is present in the sample.
    • b. If the test strip exposed to the sample initially shows an obvious yellow color but does not retain it until after 5 min, judge that methyl mercaptan is present in the sample.
• Quantitative calculation formula: not provided in the available source (this method is qualitative and reports "present" or "absent").
• Relationship between degree of color change and content (principle description): the degree of color change goes from yellow to black as the amount of hydrogen sulfide present increases.

10. Precision

Not provided in the available source.

11. Report

Report as "present" or "absent" hydrogen sulfide.

12. Referenced documents

• ISO 8819—1987 "Liquefied petroleum gas hydrogen sulfide test method (lead acetate method)" (equivalently adopted).
• GB 11125-89 "Liquefied petroleum gas hydrogen sulfide test method (lead acetate method)" (void from the date of implementation of this standard).
• No other list of normative referenced documents is 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