SH/T 0578-1994 Emulsion pH value determination method

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 name / English name / replacement relationship

• Standard number: SH/T 0578-94 (confirmed in 2004)
• Chinese name: Emulsion pH value determination method
• English name: not provided in the available source
• Replacement relationship: not provided in the available source

2. Scope of application and non-applicability

• Scope of application: This standard applies to emulsions for metalworking.
• Non-applicability: not provided in the available source.

3. Method principle

The emulsion sample is placed in a 100mL beaker, and its pH value is determined with a pH meter.

4. Reagents and materials (purity / preparation)

Unless otherwise specified, all reagents used in the test are of analytical grade; whenever water is involved, distilled water or water of equivalent purity shall be used. At a temperature of 20℃, the pH value of distilled water shall be 6.0～7.0.

• 4.1 Potassium hydrogen phthalate
• 4.2 Potassium dihydrogen phosphate
• 4.3 Disodium hydrogen phosphate
• 4.4 Sodium tetraborate (Na₂B₄O₇·10H₂O)
• 4.5 Potassium chloride: prepare a saturated solution
• 4.6 95% ethanol
• Material: filter paper

Preparation of buffer solutions:

• 5.2.1 Buffer solution with a pH value of 4.01: weigh potassium hydrogen phthalate 10.21g that has been dried at 105～110℃ for 1h, weighed to the nearest 0.01g, dissolve it in fresh distilled water, and dilute to 1L. At 20℃, the pH value of this solution is 4.01.
• 5.2.2 Buffer solution with a pH value of 6.88: weigh potassium dihydrogen phosphate 3.40g that has been dried at 105～110℃ for 1h, weighed to the nearest 0.01g, then weigh disodium hydrogen phosphate 3.55g that has been dried at 105～110℃ for 1h, weighed to the nearest 0.01g, dissolve both in fresh distilled water, and dilute to 1L. At 20℃, the pH value of this solution is 6.88.
• 5.2.3 Buffer solution with a pH value of 9.22: weigh 3.81g of sodium tetraborate, weighed to the nearest 0.01g, dissolve it in fresh distilled water, and dilute to 1L. At 20℃, the pH value of this solution is 9.22.
• Note: Commercially available buffer agents or prepared buffer solutions may be used.

5. Instruments and equipment

• 3.1.1 pH meter: accuracy 0.1pH.
• 3.1.1.1 Glass electrode: type 231.
• 3.1.1.2 Calomel electrode: type 232.
• 3.1.2 Electromagnetic stirrer: with a glass stirring bar.
• 3.1.3 Balance: sensitivity 0.2g (requires confirmation against the source standard (source-text extraction), the source text reads "sensitivity is. 2g").
• 3.1.4 Beaker: 100mL.
• 3.1.5 Wash bottle: 500mL.

6. Recommended operating conditions

• Instrument calibration: turn on the power of the pH meter, stabilize for 30min, then adjust according to the instrument instructions. Immerse the electrode in the selected buffer solution, adjust the temperature adjustment knob of the pH meter to match the temperature of the buffer solution, then adjust the "positioning" knob of the instrument so that the displayed pH value of the instrument is consistent with the pH value of the buffer solution.
• For the comparison of the pH value of buffer solutions with temperature, see the table below (the table header in the source text has source-text extraction noise, and some values require confirmation against the source standard (source-text extraction)):

• 5.4.2 Rinse the electrode with distilled water and blot it dry with filter paper, then immerse the electrode in another buffer solution; at this time, the difference between the value displayed by the pH meter and the pH value of the buffer solution shall be within the 0.05pH value. If it does not match, it indicates that the electrode is faulty, and the electrode shall be replaced and recalibrated (the range of pH values of the two buffer solutions used for calibration shall include the pH value of the sample to be tested).

7. Sampling and sample preparation

5.1 Preparation of emulsion sample: in a 100mL beaker, weigh 49g (or 47.5g) distilled water, then weigh in 1g (or 2.5g) soluble oil. Prepare an emulsion sample with a concentration of 2% (m/m) or 5% (m/m), for use in determining its pH value.

8. Analytical procedure

• 6.1 Insert the glass electrode and calomel electrode into the beaker containing the emulsion sample of 2% (m/m) or 5% (m/m) already prepared in 5.1; add a glass stirring bar to the beaker, then place it on a magnetic stirrer and stir evenly. After the indicated value stabilizes, record the pH value of the sample.
• 6.2 Lift the electrode, rinse it with 95% ethanol and distilled water, and blot it dry with filter paper.

Preparation of the electrode system:

• 5.3.1 Glass electrode: a new electrode shall be soaked in distilled water for 24h before use; after the test, the electrode shall be rinsed with 95% ethanol and distilled water, then soaked in distilled water for later use. After the electrode has been used continuously for one week, if the surface of the electrode bulb is contaminated, the electrode bulb may be soaked in cold chromic acid cleaning solution for 30s, then rinsed clean with distilled water, and then soaked in distilled water for later use. Note: chromic acid cleaning solution is dangerous, can easily cause severe burns, and is a strong oxidant, hygroscopic agent, and toxic substance.
• 5.3.2 Calomel electrode: the saturated potassium chloride solution in the calomel electrode shall be maintained at a certain height. When not in use, put the rubber sleeve on; after continuous testing for one week, the saturated potassium chloride solution shall be washed out and replaced with fresh saturated potassium chloride solution. Note: the electrode must be cleaned thoroughly; otherwise, during testing, impurities remaining on the electrode surface will cause a liquid contact potential, thereby causing deviation in the test results.
• 5.3.3 When installing the glass electrode, the lower glass bulb must be slightly higher than the ceramic core end of the calomel electrode to avoid breaking the glass bulb.

9. Qualitative and quantitative determination and calculation formula

not provided in the available source (this standard is for direct determination of the pH value, and there is no calculation formula).

10. Precision

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

• Repeatability: the difference between two results obtained by repeated determination by the same operator shall not be greater than the 0.2pH value.
• Reproducibility: the difference between two results submitted by different laboratories shall not be greater than the 0.5pH value.

11. Report

Take the arithmetic mean of two results from repeated determination as the pH value of the sample (the result shall be taken to one decimal place).

12. Referenced documents

not 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