SH/T 0621-1995 Determination of chloride content in engine coolants

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.

Source limitations: Some chemical names, units and calculation characters in the available source are ambiguous. Section 13 lists these uncertainties. The source quick-reference answer about pretreatment omits a condition given in the Principle section; that difference is identified below. Check the original standard before use.

Card type: Test method

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

• Standard number: SH/T 0621-95
• Chinese title, translated: Determination of chloride content in engine coolants
• English name in the source: not found in the available source.
• Replacement relationship: not found in the available source.
• Other information: approved on 1995-06-15; implemented on 1995-10-01; confirmed in 2004.
• Equivalent adoption stated in the source card: ASTM D3634-88, Standard Test Method for Chloride Ion in Engine Coolants.

2. Scope and exclusions

• This standard specifies a method for determining chloride content in engine coolants.
• Applies to engine coolants or concentrates containing no more than 0.6% (m/m) mercaptobenzothiazole, over a chloride-content range of 5~200 ppm.
• Also applies to engine coolants or concentrates containing aryltriazoles.
• Other substances that react with silver ions interfere with the determination.

3. Principle

First adjust the sample pH to 12~13, then add hydrogen peroxide solution to oxidize the mercaptobenzothiazole to a soluble sulfonate. Dissolve the treated sample in glacial acetic acid and titrate potentiometrically with 0.01 mol/L silver nitrate standard titration solution. Silver chloride has very low solubility in this system; at very low chloride-ion concentrations, a distinct titration inflection point cannot be obtained. In that case, add an appropriate amount of chloride to the glacial acetic acid and correct by blank titration. Coolants or concentrates containing aryltriazoles but no mercaptobenzothiazole may be determined directly without hydrogen peroxide pretreatment.

4. Reagents and materials (purity / preparation)

• 5.2.1 Distilled water: meeting the grade-three water requirements of GB/T 6682.
• 6.1 Silver nitrate: analytical grade.
• 6.2 Potassium chloride: analytical grade.
• 6.3 Sodium hydroxide: analytical grade; prepare a 250 g/L solution. Note: store in a glass bottle with paraffin-coated inner walls or in an alkali-resistant plastic bottle.
• 6.4 Glacial acetic acid: analytical grade.
• 6.5 Hydrogen peroxide, 30%: analytical grade.
• 6.6 Acetone: analytical grade.
• Note: most reagents used in this standard are toxic and corrosive. Avoid direct contact and inhalation. In the event of contact, rinse with plenty of water.
• 7.1 Potassium chloride solution: dissolve 0.20 g±0.02 g of potassium chloride in 100 mL of distilled water. The source states that each millilitre of this solution contains 1 mg of chloride ion.
• 7.2 Preparation of 0.01 mol/L silver nitrate standard titration solution: prepare and standardize a 0.05 mol/L solution according to SH/T 0079. Accurately transfer 20 mL of the standardized 0.05 mol/L solution into a 100 mL volumetric flask. Dilute to the mark with distilled water and mix to obtain a 0.01 mol/L solution. Calculate its actual concentration.
• 7.3 Titration solvent: withdraw 100 mL of glacial acetic acid from a glass bottle containing 2.3 kg of the acid. Carry out a solvent blank by potentiometrically titrating the 100 mL portion with 0.01 mol/L silver nitrate standard titration solution. If the blank consumes more than 0.2 mL of the 0.01 mol/L solution, the acid in this bottle is unsuitable and shall not be used. If it consumes less than 0.05 mL of the 0.01 mol/L solution, add an appropriate amount of potassium chloride solution, no more than 1 mL, to the acid remaining in the bottle. Mix thoroughly and titrate another 100 mL portion, aiming for a blank consumption of approximately 0.1 mL of 0.01 mol/L silver nitrate standard titration solution. Perform two accurate solvent blank determinations; their difference shall not exceed 0.02 mL. Keep the solvent for use and run a solvent blank before each test.

5. Apparatus

• 5.1.1 pH meter and titration apparatus: the pH meter shall have an accuracy of at least 2 mV. Use a silver indicator electrode and a glass reference electrode. If necessary, polish the silver electrode with steel wool or scouring powder and clean thoroughly. Note: clean and calibrate the electrodes according to the instrument instructions.
• 5.1.2 Microburette: 5 mL, graduated in 0.02 mL divisions.
• 5.1.3 Tall-form beakers: 250 mL.
• 5.1.4 Pipettes: 5, 10, 20 and 100 mL.
• 5.1.5 Reflux apparatus: a 250 mL conical flask fitted with a condenser having a jacket length of 300 mm.
• 5.1.6 Volumetric flasks: 100 and 200 mL.
• Note: clean glassware with chromic acid cleaning solution, rinse with plenty of tap water, then rinse with acetone and dry.

6. Recommended operating conditions

• Silver nitrate standard titration solution concentration: 0.01 mol/L.
• Sample pH adjustment: 12~13.
• Reflux time: 30 min.
• Near the endpoint, add titrant in 0.02 mL increments.
• Plot the E-V curve with potential E on the vertical axis at 2 mV per small division, and titration volume V on the horizontal axis at 0.02 mL per small division.
• Other conditions: not found in the available source.

7. Sampling and sample preparation

• 7.4 Sampling: follow SH/T 0065.
• 8.1 Sample treatment: add 50 g±0.1 g of engine coolant sample and approximately 30 mL of distilled water to a 250 mL conical flask. Add 5 mL of 250 g/L sodium hydroxide solution to obtain a pH of 12~13, then add 5 mL of 30% hydrogen peroxide solution and stir. Fit the condenser to the flask and heat under reflux for 30 min. After cooling to room temperature, transfer all the solution to a 200 mL volumetric flask and dilute to the mark with distilled water.
• 8.2 Blank solution: add 5 mL of 250 g/L sodium hydroxide solution and 5 mL of 30% hydrogen peroxide solution to another 200 mL volumetric flask. Dilute to the mark with distilled water for the blank test.

8. Procedure

• 8.3 Pipette 100 mL of glacial acetic acid into each of two 250 mL tall-form beakers. Accurately add 20 mL of the coolant sample treated under clause 8.1 to one beaker, and 20 mL of the blank solution prepared under clause 8.2 to the other. Mix. With slow magnetic stirring, titrate each solution potentiometrically with 0.01 mol/L silver nitrate standard titration solution. Potential equilibration takes longer near the endpoint; add titrant in 0.02 mL increments and allow sufficient time for a stable reading. Record the potential in mV and the corresponding titration volume in mL.
• 8.4 Plot an E-V curve from the potentials and corresponding titration volumes. The endpoint is at the midpoint of the steepest part of the curve (see the source figure). Read from the curves the volumes, in mL, of silver nitrate standard titration solution consumed at the endpoints for the blank and sample solutions.

9. Determination and calculation

Calculate sample chloride content X [ppm(m/m)] using:

X = (V - V₀)c × 0.0355 × 200 × 10⁶ / (20 × m) = (V - V₀)c × 355000 / m

Where:

• V — volume of silver nitrate standard titration solution consumed by the sample, mL;
• V₀ — volume of silver nitrate standard titration solution consumed by the blank, mL;
• c — actual concentration of the silver nitrate standard titration solution, mol/L;
• m — mass of the sample, g;
• 0.0355 — mass of chloride in grams equivalent to 1.00 mL of silver nitrate standard titration solution [c(AgNO₃)=1.000 mol/L];
• 200 — prepared sample-solution volume, mL;
• 20 — sample-solution volume used in the test, mL.

10. Precision

• 10.1 Reproducibility: the difference between two results submitted by different laboratories shall not exceed 5 ppm.

11. Report

Report the chloride content of the engine coolant to 1 ppm.

12. References

• GB/T 6682 Water for analytical laboratory use — Specification and test methods.
• SH/T 0065 Sampling of engine coolants or antirust agents and preparation of their aqueous solutions.
• SH/T 0079 Preparation of reagent solutions for petroleum-product tests.
• ASTM D3634-88, stated by the source card to be equivalently adopted.

13. Source limitations and verification

• Source extraction uncertainties requiring confirmation (source-text extraction):
  • The filename includes fragments '(599) Appendix I', '(603) Appendix II' and '(607) Volume IV contents', suggesting that compilation contents pages may have been included; these are not standard body text.
  • The extracted chemical names are garbled, including one fragment containing '4 1'. The source card tentatively reads the names as mercaptobenzothiazole and aryltriazoles; these readings require verification.
  • The extracted term interpreted as 'pH value' is garbled and requires verification.
  • The beaker description contains the garbled numeric fragment '4 9'; the source card tentatively reads it as 'tall-form beaker'.
  • Strings such as '100ML', '200ni l', 'O.Olmol/L' and 'moUL' have suspect capitalization or units caused by source extraction.
  • In the extracted expression '0.20g [unreadable sign] 0.02g', the source card tentatively interprets the sign as ±.
  • The extracted '5f nL' is suspected to mean '5 mL'.
  • The extracted '100' followed by garbled text and 'glacial acetic acid' is suspected to mean '100 mL glacial acetic acid'.
  • The extracted term interpreted as 'chloride content' is garbled.
  • The unclear character between V and Vo in the extracted calculation expression '(V [unclear character] Vo)c' is suspected to be the minus sign '-'.
  • The extracted figure caption is garbled; the source card tentatively reads it as 'Titration curve for determination of chloride content in engine coolant'.

14. Quick reference questions