SH/T 0069-1991 Determination of pH value of engine antifreeze, rust inhibitor and coolant

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 0069-91
• Chinese name: Determination of pH value of engine antifreeze, rust inhibitor and coolant
• English name: not provided in the available source
• Replacement relationship: not provided in the available source (the source marks "(200(! year confirmation)", suspected to be "2000 year confirmation", requires confirmation against the source standard (source-text extraction))
• Reference adoption: ASTM D1287-85 "Determination of pH value of engine antifreeze, rust inhibitor and coolant"
• Approval/implementation: approved by China Petrochemical Corporation 1991-06-28, implemented on 1992-07-01

2. Scope of application and non-applicability

• Applicable to: concentrates of engine antifreeze, rust inhibitor and coolant, and water dilutions of these product concentrates, whether used or unused.
• Not applicable to: solid rust inhibitors.

3. Method principle

Measure 100 mL of sample, inject into 150 mL beaker, use pH meter to determine its pH value. Note: When determining the pH value of a concentrated product, according to the general concept the meter reading is not the measured pH value, but the apparent pH value, which is very useful when analyzing product condition.

4. Reagents and materials (purity / preparation)

Unless otherwise specified, all test reagents are of analytical grade; whenever water is involved, distilled water or water of equivalent purity shall be used. At 25℃, the pH value of distilled water should be 6.2～7.2 (the source says "6.2[unreadable separator]7.20", requires confirmation against the source standard (source-text extraction)).

Reagents:

• 5.1 Potassium hydrogen phthalate
• 5.2 Potassium dihydrogen phosphate
• 5.3 Sodium dihydrogen phosphate
• 5.4 Sodium tetraborate (Na₂B₄O₇·10H₂O)
• 5.5 Potassium chloride: prepare as saturated solution

Buffer solution preparation:

• 6.2.1 Buffer solution with pH value of 4.01: weigh potassium hydrogen phthalate 10.21 g that has been dried at 105～110℃ for 1 h (the source says "10.218", requires confirmation against the source standard (source-text extraction)), weigh to 0.01 g, dissolve in fresh distilled water, dilute to 1 L. At 25℃, the pH value is 4.01.
• 6.2.2 Buffer solution with pH value of 6.86: weigh potassium dihydrogen phosphate 3.40 g that has been dried at 105～110℃ for 1 h (the source says "3.408", requires confirmation against the source standard (source-text extraction)), weigh to 0.01 g; then weigh disodium hydrogen phosphate 3.55 g that has been dried at 105～110℃ for 1 h (the source says "3.558", requires confirmation against the source standard (source-text extraction)), weigh to 0.01 g; dissolve both in fresh distilled water, dilute to 1 L. At 25℃, the pH value is 6.86.
• 6.2.3 Buffer solution with pH value of 9.18: weigh 3.81 g sodium tetraborate (the source says "3.818", requires confirmation against the source standard (source-text extraction)), weigh to 0.01 g, dissolve in fresh distilled water, dilute to 1 L. At 25℃, the pH value is 9.18.
• 6.2.4 Buffer solution with pH value of 11.72: weigh disodium hydrogen phosphate 1.42 g that has been dried at 105～110℃ for 1 h, weigh to 0.01 g, dissolve in 100 mL sodium hydroxide solution of concentration 4 g/L, and dilute with fresh distilled water to 1 L. At 25℃, the pH value is 11.72.
• Note: Commercially available buffers or prepared buffer solutions may be used.

Materials:

• 4.2 a. Filter paper
• 4.2 b. Absorbent cotton

5. Instruments and equipment

• 4.1 a. pH meter: precision of 0.1 pH value (the source says "[unreadable character].1 pH value", requires confirmation against the source standard (source-text extraction))
• 4.1 b. Glass electrode: 231 type
• 4.1 c. Calomel electrode: 232 type
• 4.1 d. Beaker: 150 mL (the source says "[unreadable value](h[unreadable unit]", requires confirmation against the source standard (source-text extraction))
• 4.1 e. Graduated cylinder: 100 mL (the source says "1[unreadable character]ML", requires confirmation against the source standard (source-text extraction))

6. Recommended operating conditions

• Instrument calibration: turn on the power of the pH meter, stabilize for 30 min, adjust according to the instrument manual. Immerse the electrode in the selected buffer solution, shake a few times, observe the temperature of the buffer solution, adjust the temperature adjustment knob of the pH meter to match the temperature of the buffer solution, adjust the pointer for measuring the pH value so that its indicated value matches the pH value of the buffer solution.
• Rinse the electrode with distilled water, blot the water on the electrode dry with filter paper, then immerse the electrode in another buffer solution; the difference between the reading of the pH meter and the pH value of the buffer solution should be within 0.05 pH value; if not, it indicates the electrode is faulty, and the electrode should be replaced and recalibrated (the pH value range of the two buffer solutions used for calibration should include the pH value of the sample being tested).
• Electrode preparation: A new glass electrode should be soaked in distilled water for 24 h before use; after the test, the electrode should be rinsed clean with distilled water and soaked in distilled water for later use. After one week of continuous use, if the surface of the electrode bulb is contaminated, the electrode bulb may be soaked in cold chromic acid cleaning solution for 30 s, then rinsed clean with distilled water, and then soaked in distilled water for later use. Note: Chromic acid cleaning solution is dangerous, easily causing severe burns, and is a strong oxidant, hygroscopic agent and toxic substance.
• Calomel electrode: The internal saturated potassium chloride solution must be maintained at a certain height; when not in use, put on the two rubber sleeves; after one week of continuous use, the saturated potassium chloride solution should be washed off and replaced with new saturated potassium chloride solution.

7. Sampling and sample preparation

• 6.1.1 Sampling of concentrate samples: carry out according to SH/T 0065.
• 6.1.2 Preparation of dilution samples: carry out according to SH/T 0065. For dilution requirements, it is recommended that the concentration of engine coolant and antifreeze be 50% (V/V) or 33% (V/V). The concentration of the rust inhibitor solution should be within the use range.
• 6.1.3 For unused samples or prepared diluted solutions, if a small amount of insoluble liquid layer appears, it should be separated with a separatory funnel before the test.

8. Analytical procedure

• 7.1 Measure 100 mL of sample and inject into 150 mL beaker, place the beaker on the stand of the pH meter, immerse the two prepared electrodes in the sample, stir for 3～5 min to bring the entire system to equilibrium.
• 7.2 Turn on the measurement switch on the pH meter; when the instrument pointer stabilizes at a certain value, record this value.
• Note ①: If there is an oil film on the glass electrode, it should be removed with a mixed solvent of 1:1 (V/V) toluene and ethyl acetate.
• Note ②: For antifreeze containing silicates, it is necessary to specify the pH value reading as follows:
  • a. When the test is carried out immediately after preparing the dilution, record the pH value reading promptly.
  • b. After allowing the solution to stand for a period of time, for example 30 min, record the pH value reading again. By comparison, it can be seen that the pH value shown after an interval of 30 min is lower than the pH value obtained by direct experiment by 0.2 pH value. Through determination it is concluded that: if the concentrate is diluted and after 24 h the measured pH value is lower than the pH value obtained by direct experiment by 0.3～0.5 pH value (the source says "[unreadable leading character]3[unreadable separator]0.5 pH value", requires confirmation against the source standard (source-text extraction)).

9. Qualitative and quantitative determination and calculation formula

not provided in the available source (this standard is direct instrumental determination, no calculation formula).

10. Precision

• 8.1 Repeatability: by the same operator, the difference between two results of repeated determination should not be greater than 0.1 pH value.
• 8.2 Reproducibility: the difference between two results submitted by different laboratories should not be greater than 0.2 pH value.

11. Report

Take the arithmetic mean of the two results of repeated determination as the test result, and take it to 0.1 pH value.

12. Referenced documents

• SH/T 0065 Sampling of test samples of engine coolant or rust inhibitor and preparation of their aqueous solutions
• ASTM D1287-85 (reference adoption)

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