SH/T 0205-1992 Determination of refractive index and specific dispersion of electrical insulating liquids

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: SH/T 0205-92 (confirmed in 2004)
• Chinese title: Determination of refractive index and specific dispersion of electrical insulating liquids
• English title: not provided in the available source
• Replacement relationship: replaces ZB E38 001-88
• Reference adoption: conventional part of ASTM D1807-84(1989) "Determination of refractive index and specific dispersion of electrical insulating liquids"
• Approval/implementation: approved by China Petrochemical Corporation 1992-05-20, implemented on 1992-05-20

2. Scope of application and non-applicability

• Applicable: This standard specifies the method for determining the refractive index and specific dispersion of electrical insulating liquids; it is applicable to transparent, light-colored electrical insulating liquids used in transformers, capacitors, oil-filled cables, circuit breakers, and similar equipment.
• Not applicable: not provided in the available source.

3. Method principle

Under specified test conditions, determine the refractive index, Z value, and density of the sample. Obtain the numerical value of the specific dispersion of the sample through table lookup and conversion.

4. Reagents and materials (purity / preparation)

• 5.2.1 Qualitative filter paper
• 5.2.2 Absorbent cotton (the source source-text extraction is "[garbled absorbent-cotton name]", requires confirmation against the source standard (source-text extraction))
• 6.1 Calcium chloride: chemically pure
• 6.2 Diethyl ether: analytically pure
• 6.3 Petroleum ether: 60～90℃, analytically pure (the source source-text extraction is "60[unreadable separator]9090", requires confirmation against the source standard (source-text extraction))

5. Instruments and equipment

• 5.1.1 Abbe refractometer: used in the conventional method with a measurement range of approximately 1.33～1.50, minimum scale value 0.001, and the prism part can be thermostatted.
• 5.1.2 Light source: natural light or fluorescent lamp.
• 5.1.3 Constant-temperature water bath: capable of supplying water to the insulation jacket of the Abbe refractometer to keep the prism at constant temperature and maintain the temperature within the range of ±0.1℃.
• 5.1.4 Density meter: complies with the type SY-I specified in SH/T 0316.

6. Recommended operating conditions

• Prism constant temperature: 25℃±0.1℃ or the temperature required by the test (7.4).
• Light source: natural light or fluorescent lamp (5.1.2).
• Temperature stabilization time: after closing the two prism surfaces, wait for the temperature to stabilize for 2 min before measurement (8.1, the source source-text extraction is "2nun", requires confirmation against the source standard (source-text extraction)).

7. Sampling and sample preparation

• 7.1 When the sample contains water or other mechanical impurities, dehydrate with anhydrous calcium chloride and filter with dry filter paper.
• 7.2 Periodically inspect and calibrate the refractometer according to the instrument manual.
• 7.3 Before testing, clean the instrument according to the instrument manual. If the instrument does not provide special instructions, gently wipe the two prism surfaces and the metal surface fixing the prisms with absorbent cotton soaked in diethyl ether or petroleum ether until no residual oil remains.
• 7.4 Turn on the constant-temperature water bath to keep the prism temperature constant at 25℃±0.1℃ or the temperature required by the test.

8. Analysis procedure

• 8.1 Use a clean round-headed glass rod to take 1 drops of sample and place them on the surface of the refracting prism, taking care not to introduce air bubbles, then close the two prism surfaces. After the temperature has stabilized for 2 min, perform the measurement.
• 8.2 Turn the prism handwheel to make the light-dark boundary in the eyepiece field of view clear. Read the refractive index to three decimal places and estimate the fourth decimal place. Repeat the measurement three times and take the arithmetic mean of the above data as the refractive index of the sample.
• 8.3 Turn the Amici prism handwheel to eliminate the color of the light-dark boundary in the eyepiece field of view, and accurately read the Z value at the forward and reverse positions of the compensator dial to two digits, and estimate one digit after the decimal point. Repeat the measurement three times, read six data, and take their arithmetic mean as the measurement result.
• 8.4 Measure the apparent density of the sample according to GB/T 1884, and calculate the density of the sample at 25℃ according to GB/T 1885.

9. Qualitative and quantitative determination and calculation formulas

• Definitions:
  • 3.1 Refractive index: the ratio of the speed of light in air to the speed of light in the substance being tested.
  • 3.2 Dispersion value: under specified temperature conditions, use the refractive index and Z value measured from the sample to look up the table and obtain A, B, S values, and calculate the result according to the dispersion value C=A+B·S, which is the dispersion value (the source source-text extraction is "C[unreadable symbol]A[garbled symbols]", requires confirmation against the source standard (source-text extraction)).
  • 3.3 Specific dispersion: the dispersion value of the sample divided by the density at the same temperature, then multiplied by 100, is the specific dispersion (the source source-text extraction is "dispersion divided by density at the same temperature, multiplied by 100. gives specific dispersion [wording garbled]", requires confirmation against the source standard (source-text extraction)).
• Calculation: Using the measured refractive index and Z value, calculate the specific dispersion X according to the "Abbe Refractometer Dispersion Table" provided in the instrument manual and the following formula:
  • X = C / ρ × 100 (the source formula source-text extraction is "X=[unreadable symbols]1[unreadable character]", requires confirmation against the source standard (source-text extraction))
  • Where: C— dispersion value; ρ— density of the sample at 25℃.
• Round the result to an integer according to the rules for rounding off significant figures.

10. Precision

Judge the reliability of the test results according to the following provisions (95% confidence level).

• Repeatability: the difference between two results obtained by the same operator in repeated measurements shall not exceed the following values:
  • Refractive index: 3×10⁻⁴
  • Specific dispersion: 3

11. Report

Take the arithmetic mean of two measurement results as the test result.

• 11.1 Refractive index: report the result to four decimal places and state the test temperature.
• 11.2 Specific dispersion: report the result as an integer.
• 11.3 Report the light source used during the test.

12. Referenced documents

• GB/T 1884 Standard test method for density of crude petroleum and liquid petroleum products by laboratory determination (hydrometer method)
• GB/T 1885 Petroleum measurement tables
• SH/T 0316-92 Specification for petroleum hydrometers (the source source-text extraction is "SH/T 0316[unreadable year separator and character]2", requires confirmation against the source standard (source-text extraction))

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