SH/T 0329-1992 Determination of free alkali and free organic acid in lubricating grease

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 title / replacement relationship

• Standard number: SH/T 0329-1992 (confirmed in 2004)
• Chinese title: Determination of free alkali and free organic acid in lubricating grease
• English title: not provided in the available source
• Replacement relationship: replaces SY 2707—79 (82)
• First issued: 1954 (see additional notes)
• Approval/implementation: approved by China Petrochemical Corporation on 1992-05-20, implemented on 1992-05-20

2. Scope of application and non-applicability

• This standard specifies the determination of the content of free alkali and free organic acid in lubricating greases thickened by alkali metal and alkaline earth metal soaps.
• This standard applies to lubricating greases.
• Not applicable: not provided in the available source.

3. Method principle

Add the lubricating grease sample to a solvent naphtha (or benzene)-ethanol mixed solvent, and heat under reflux until the sample is completely dissolved. Using phenolphthalein as indicator, titrate its free alkali with a hydrochloric acid standard volumetric solution, or titrate its free organic acid with a potassium hydroxide ethanol standard volumetric solution.

4. Reagents and materials (purity / preparation)

4.1 Reagents

• 3.1.1 95% Ethanol: analytical reagent. Prepare a 60% ethanol aqueous solution by mixing 7.5 volumes of 95% ethanol with 3.5 volumes of distilled water.
• 3.1.2 Potassium hydroxide: analytical reagent. Prepare a potassium hydroxide ethanol standard volumetric solution with purified ethanol [c(KOH)=0.05 mol/L].
• 3.1.3 Hydrochloric acid: analytical reagent. Prepare a hydrochloric acid standard volumetric solution with distilled water [c(HCl)=0.05 mol/L].
• 3.1.4 Benzene: analytical reagent.
• 3.1.5 Phenolphthalein: prepare a 10 g/L ethanol indicator solution.

4.2 Materials

• Solvent naphtha for the rubber industry.

5. Apparatus and equipment

• 4.1 Ground-glass-stoppered conical flask or conical flask: 250~300 mL.
• 4.2 Microburette: 2 mL, with graduations of 0.02 mL.
• 4.3 Snake-shaped or bulb condenser tube: about 300 mm in length.
• 4.4 Electric heating plate or water bath.
• 4.5 Scraper.
• 4.6 Beaker or porcelain cup.
• 4.7 Graduated cylinder: 50 mL and 100 mL.

6. Recommended operating conditions

• Dissolution method: heat under reflux until the sample is completely dissolved.
• Boiling time: boil the mixture for 5 min; after the sample dissolves, continue boiling for 5 min.
• Titration temperature: neutralize while hot; before titration, cool to room temperature.
• Titration time: titration should be carried out continuously but not exceeding 3 min.
• Indicator: phenolphthalein ethanol indicator solution, 3~4 drops.
• Difficultly soluble samples: benzene may be used instead of solvent naphtha.
• Greases with relatively high soap content and dark-colored greases: it is permissible to add solvent naphtha 60 mL and 60% ethanol 40 mL (Note).

7. Sampling and sample preparation

• 5 Preparation: stir uniformly.
• 6 Test procedure: scrape off the surface of the sample with a scraper, then take approximately equal amounts of sample from at least three locations not close to the container wall, and place them in a small beaker.
• 6.1 Sample mass:
  • General samples: 2~3 g, accurate to 0.001 g;
  • Viscous and difficultly soluble lubricating greases: 1~1.5 g, accurate to 0.001 g;
  • Lubricating greases containing free organic acid below 0.1: may weigh 4~5 g, accurate to 0.1 g (the source text says "accurate to 0.1go", requires confirmation against the source standard (source-text extraction)).

8. Analytical procedure

• 6.2 In another clean, dry ground-glass-stoppered conical flask, add solvent naphtha 30 mL and 60% ethanol 20 mL, stopper with a ground-glass-stoppered reflux condenser or with a cork wrapped in tin foil on the condenser, and while shaking continuously, boil the mixture for 5 min. For samples difficult to dissolve in solvent naphtha, benzene may be used instead of solvent naphtha.
  • Note: For lubricating greases with relatively high soap content and dark-colored lubricating greases, it is permissible to add solvent naphtha 60 mL and 60% ethanol 40 mL.
• To the boiled solvent naphtha-ethanol mixture, add 3~4 drops of phenolphthalein ethanol indicator solution, and while shaking continuously, neutralize while hot with potassium hydroxide ethanol standard volumetric solution (3.1.2) until a pale rose-red color appears.
• 6.3 Pour the neutralized solvent naphtha-ethanol mixture into the ground-glass-stoppered conical flask containing the weighed sample, and stopper with a ground-glass-stoppered reflux condenser or with a cork wrapped in tin foil on the condenser. While shaking continuously, boil until the sample is completely dissolved, then continue boiling for 5 min, then remove from the condenser, stopper the conical flask containing the mixture with the tin foil-wrapped cork, and while shaking continuously, cool to room temperature with cooling water.
• Add 3~4 drops of phenolphthalein ethanol indicator solution to the mixture, and titrate while shaking continuously:
  • If the ethanol-water layer is rose-red, titrate with hydrochloric acid standard volumetric solution (3.1.3) until the color disappears;
  • If the ethanol-water layer is colorless, titrate with potassium hydroxide ethanol standard volumetric solution until a pale rose-red color appears.
  • Titration should be carried out continuously but not exceeding 3 min.

9. Qualitative and quantitative determination and calculation formulas

7.1 Free alkali X [expressed as NaOH% (m/m)] is calculated according to formula (1):

X = V·c×0.040×100 / m (the source text source-text extraction is "X=1c×0.040×100-70×4.0", the formula appears to contain noise, requires confirmation against the source standard (source-text extraction))

• V: volume of hydrochloric acid standard volumetric solution (3.1.3) consumed in titrating the sample mixture, mL;
• c: actual concentration of the hydrochloric acid standard volumetric solution (3.1.3), mol/L;
• m: mass of the sample, g;
• 0.040: mass, expressed in grams, of alkali (expressed as sodium hydroxide) equivalent to 1.00 mL hydrochloric acid standard volumetric solution [c(HCl)=1.000 mol/L].

7.2 The free organic acid content is expressed as acid value or as a percentage.

7.2.1 Acid value K (mgKOH/g) is calculated according to formula (2):

K = V·c×0.0561×1000 / m (the source text source-text extraction is "K=Yc×0.0561×1000", requires confirmation against the source standard (source-text extraction))

• V: volume of potassium hydroxide ethanol standard volumetric solution (3.1.2) consumed in titrating the sample mixture, mL;
• c: actual concentration of the potassium hydroxide ethanol standard volumetric solution (3.1.2), mol/L;
• m: mass of the sample, g;
• 0.0561: mass, expressed in grams, of acid (expressed as potassium hydroxide) equivalent to 1.00 mL potassium hydroxide ethanol standard volumetric solution [c(KOH)=1.000 mol/L].

7.2.2 Free organic acid X [converted to oleic acid % (m/m)] is calculated according to formula (3):

X = V·c×0.2825×100 / m (the source text source-text extraction is "X=Y:C×0.2825×100-Y:0×28.25", requires confirmation against the source standard (source-text extraction))

• V: volume of potassium hydroxide ethanol standard solution (3.1.2) consumed in titrating the sample mixture, mL;
• c: actual concentration of the potassium hydroxide ethanol standard solution (3.1.2), mol/L;
• m: mass of the sample, g;
• 0.2825: mass, expressed in grams, of oleic acid equivalent to 1.00 mL potassium hydroxide ethanol standard volumetric solution [c(KOH)=1.000 mol/L].

10. Precision

8.1 Repeatability

• 8.1.1 The difference between two results of repeated determination of free alkali shall not exceed 0.02% (m/m).
• 8.1.2 The difference between two results of repeated determination of acid value shall not exceed the following values:

• 8.1.3 The difference between two results of repeated determination of free organic acid shall not exceed 0.02% (m/m) (converted to oleic acid).

11. Report

• 9.1 Take the arithmetic mean of two results of repeated determination as the determination result of free alkali or free organic acid in the sample.
• 9.2 When the free alkali content in the sample is below 0.02% (m/m), it is judged as none.

12. Referenced documents

• not provided in the available source (the main text does not list a normative referenced documents list).

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