SH/T 0196-1992 Determination of Oxidation Stability of Lubricating Oils

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Card type: Test method

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

• Standard number: SH/T 0196-92
• Chinese name: Determination of Oxidation Stability of Lubricating Oils
• English name: not provided in the available source
• Replacement relationship: replaces zB E34 014-88
• First issued: 1954 year
• Reference adoption: Soviet national standard ГОСТ 981-52 "Determination of Oxidation Stability of Lubricating Oils"
• Technical committee: Technical committee of the Research Institute of Petroleum Processing
• Drafting organization: Research Institute of Petroleum Processing responsible for drafting
• Approval/implementation: approved by China Petrochemical Corporation 1992-05-20, implemented on 1992-05-20

2. Scope of application and non-applicability

• This standard specifies the method for determining the oxidation stability of lubricating oils.
• This standard applies to lubricating oils.
• Not applicable: not provided in the available source.

3. Method principle

After the sample undergoes mild oxidation under specified conditions (one steel ball and one copper ball each, with continuous introduction of air 4h), its water-soluble acid is measured. After deep oxidation (low-carbon steel spiral coil, copper sheet, with continuous introduction of oxygen 8h), its acid value and sediment are measured.

4. Reagents and materials (purity / preparation)

4.1 Materials

• 4.2.1 low-carbon steel ball and T1 copper ball: diameter 5mm±0.1mm.
• 4.2.2 spiral coil: diameter 15mm, length 65mm; wound from low-carbon steel wire of diameter 1mm and length 1000mm.
• 4.2.3 copper sheet: made from T1 copper of thickness 0.2～0.3mm according to Figure 3.
• 4.2.4 compressed air.
• 4.2.5 distilled water.
• 4.2.6 chromic acid cleaning solution.
• 4.2.7 mineral oil: open flash point not lower than 250℃, for oil bath use.
• 4.2.8 abrasive cloth (or abrasive paper): grit 100 or 120.
• 4.2.9 standard isooctane.
• 4.2.10 solvent naphtha: conforms to SH 0004 specification. The solvent naphtha shall be washed twice with 70g/L sodium hydroxide solution, then washed with water and distilled water until it shows a neutral reaction when tested with phenolphthalein indicator solution, and then filtered through several layers of filter paper.
• 4.2.11 quantitative filter paper.
• 4.2.12 straight-run gasoline.

4.2 Reagents

• 5.1 nitric acid: analytical reagent.
• 5.2 phosphoric acid: analytical reagent.
• 5.3 95% ethanol: analytical reagent.
• 5.4 methanol: analytical reagent.
• 5.5 sulfuric acid: chemical reagent, for gas washing bottle use.
• 5.6 sodium hydroxide: chemical reagent, prepared as 400g/L solution, for gas washing bottle use.
• 5.7 potassium hydroxide: analytical reagent, prepared as c(KOH)=0.025mol/L potassium hydroxide standard titration solution and c(KOH)=0.05mol/L potassium hydroxide-ethanol standard titration solution.
• 5.8 alkaline blue 6B indicator: prepared as 20g/L ethanol indicator solution.
• 5.9 methyl orange indicator: prepared as 1g/L indicator solution.
• 5.10 phenolphthalein indicator: prepared as 10g/L ethanol indicator solution.
• 5.11 petroleum ether: 60～90℃, analytical reagent.
• 5.12 benzene: analytical reagent.

4.3 Solution preparation in preparatory work

• 6.1 refined gasoline: pour straight-run gasoline not containing tetraethyllead into a separatory funnel, add sulfuric acid of concentration 98%(m/m) or above, shake for 30min after each addition of sulfuric acid. For the sulfuric acid added, the first volume is equal to the gasoline, and the following two times are each half the amount of gasoline. After sulfuric acid treatment, neutralize with 30g/L sodium hydroxide solution, then wash with water until a neutral reaction is shown (identified with phenolphthalein indicator solution), and after filtering dry through one to three layers of filter paper, distill using a suitable fractionating column, and collect the fraction of 60～90℃. Methods such as molecular sieves and silica gel to remove aromatic hydrocarbons from gasoline may also be used to prepare refined gasoline. 60～90℃ petroleum ether not containing aromatic hydrocarbons may also be used.
• 6.2 nitric acid-phosphoric acid mixed solution: prepared from nitric acid and phosphoric acid in a volume ratio of 3:7.
• 6.3 ethanol-benzene mixed solution: prepared from freshly distilled 95% ethanol and freshly distilled benzene in a volume ratio of 1:4.

5. Apparatus and equipment

• 4.1.1 oxidation tube: made of glass (see Figure 1).
• 4.1.2 oil bath: equipped with electric heating device and stirring device, capable of installing at least four oxidation tubes, and capable of maintaining constant temperature at 125℃±0.5℃, adjustable by automatic temperature controller or rheostat. The depth of the oil bath shall be sufficient to completely immerse the spiral coil portion of the oxidation tube in the oil.
• 4.1.3 thermometer: 0～150℃.
• 4.1.4 gas washing bottle: for holding sodium hydroxide solution and sulfuric acid.
• 4.1.5 absorption bottle (see Figure 2): for absorbing volatile water-soluble acid, the bottle is filled with distilled water.
• 4.1.6 air flow meter: filled with kerosene and marked with air flow rate graduations of 30, 50, 100mL per minute.
• 4.1.7 oxygen flow meter: filled with kerosene and marked with oxygen flow rate graduations of 50, 200, 300mL per minute.
• 4.1.8 safety bottle (or gas washing bottle): used to prevent kerosene from rushing from the flow meter into the oxidation tube.
• 4.1.9 oxygen cylinder: with oxygen pressure reducing device.
• 4.1.10 pressure regulator: filled with water to an appropriate height.
• 4.1.11 graduated cylinder: with ground stopper, 100, 250mL.
• 4.1.12 microburette: 2mL, graduation 0.02mL.
• 4.1.13 pipette: 3, 20, 25mL.
• 4.1.14 volumetric flask: 25mL.
• 4.1.15 separatory funnel: 150mL.
• 4.1.16 condenser tube.
• 4.1.17 colorless glass test tube.
• 4.1.18 conical flask: 50, 250mL.
• 4.1.19 water bath.
• 4.1.20 stand and clamp.

6. Recommended operating conditions

• Mild oxidation: oil bath temperature 125℃±0.5℃, air flow rate 50mL per minute, continuous introduction of air for 4h.
• Deep oxidation: oil bath temperature 125℃±0.5℃, oxygen flow rate 200mL per minute, continuous introduction of oxygen for 8h.
• Sediment standing conditions: stand in the dark at temperature 20℃±3℃ for 12h.
• Sediment drying: dry in an oven at 105℃±3℃ to constant weight (difference between two consecutive weighing results not greater than 0.0004g).
• Heating conditions for water-soluble acid determination: heat in a water bath to 70℃.
• Acid value titration: use c(KOH)=0.05mol/L potassium hydroxide-ethanol standard titration solution.

7. Sampling and sample preparation

• 7.1.1 Weigh the sample 30g into a clean, dry oxidation tube, accurate to 0.1g (the source text at source-text extraction is "0.[unreadable character]", requires confirmation against the source standard (source-text extraction)).
• 7.2.1 Weigh the sample 30g into a clean, dry oxidation tube, accurate to 0.1g.
• 7.2.2 After oxidation is completed, remove the oxidation tube from the oil bath, cool to about 60℃, then stir the oxidized oil in the tube with gentle blowing to make it uniform, then inject 20～25g of the oxidized oil into a 100mL graduated cylinder with a ground stopper, accurate to 0.01g, for the determination of sediment content and acid value. And dilute the oxidized oil in the graduated cylinder with three times its volume of refined gasoline.
• If the saponification value of the oxidized oil needs to be determined, add 2～4g of the oxidized oil into a conical flask, accurate to 0.001g (the source text at source-text extraction is "0.00[unreadable character]", requires confirmation against the source standard (source-text extraction)), and determine according to GB/T 8021.
• Note: ① The total amount of refined gasoline required for dissolving and washing each portion of oxidized oil is 150～200mL (the source text at source-text extraction is "150 - 2 0 . L", requires confirmation against the source standard (source-text extraction)). ② When determining sediment content and acid value, the operations of weighing the oxidized oil and diluting with gasoline shall be carried out immediately upon completion of oxidation.

8. Analytical procedure

8.1 Determination of water-soluble acid content formed after mild oxidation of lubricating oil

• 7.1.1 Mild oxidation of lubricating oil: weigh the sample 30g into a clean, dry oxidation tube, accurate to 0.1g. Then place one steel ball and one copper ball into the sample, and plug the mouth of the oxidation tube with a clean cork or cotton; the cork or cotton must be pre-washed with benzene and dried. The test apparatus is shown in Figure 4. Immerse the oxidation tube containing the sample and metal balls in an oil bath heated to 125℃±0.5℃, so that its spiral coil portion is completely immersed in the oil bath (the liquid level in the bath shall be higher than the liquid level in the tube). Then connect the oxidation tube with a rubber tube (or plastic tube) to an absorption bottle containing 20mL distilled water, and continuously introduce air at 50mL per minute into the sample. Before the air is introduced into the sample, it is washed through a sodium hydroxide solution gas washing bottle and a sulfuric acid gas washing bottle, and the air flow rate is measured with a flow meter. The oxidation operation is continuously carried out at a temperature of 125℃ for 4h.
• 7.1.2 Determination of the non-volatile water-soluble acid content: after oxidation is completed, remove the oxidation tube from the oil bath, allow it to cool to room temperature (20℃±3℃), then immediately weigh oxidized oil 25g into a 250mL conical flask, accurate to 0.1g; add distilled water 2mL to the conical flask (the source text source-text extraction is "2mL", requires confirmation against the source standard (source-text extraction)), and immerse the conical flask in a water bath and heat to 70℃. When testing turbine oil and emulsifiable transformer oil, first add 20mL of standard isooctane or solvent naphtha to the weighed oxidized oil, then add distilled water. Pour the mixture in the conical flask into a separatory funnel and shake for 5min. After standing, place the separated aqueous layer from the separatory funnel into a conical flask of capacity 50mL. Then, use a pipette to take water extract 3mL from the conical flask, inject it into a clean test tube, and add 1 drops of methyl orange indicator solution. In another test tube, add distilled water 3mL and 1 drops of methyl orange indicator solution. Compare the color of the solutions in the two test tubes. If the color of the solutions in the two test tubes is the same, the extract is considered to have a neutral reaction. If the water extract shows an acidic reaction, add 25mL 70℃ of distilled water to the separatory funnel again and shake for 5min. After standing, place the aqueous layer into another 50mL conical flask, and again check its reaction with methyl orange indicator solution as above. Repeat this operation until the water extract shows a neutral reaction. Mix the collected portions of acidic and neutral water extracts uniformly, use a pipette to take 20mL of the mixed liquid, inject it into a 50mL conical flask, add 3 drops of phenolphthalein indicator solution, and titrate with c(KOH)=0.025mol/L potassium hydroxide standard titration solution until a light red color appears. At the same time, carry out a blank test, using 60mL of distilled water instead of the extract, and preheat it to 70℃, then cool to room temperature, add 3 drops of phenolphthalein indicator solution, and titrate with the above potassium hydroxide standard titration solution.
• 7.1.3 Determination of the volatile water-soluble acid content: after oxidation is completed, first pour the liquid in the absorption bottle into a volumetric flask of 25mL, then rinse the inner wall of the absorption bottle several times with 5mL distilled water, and the washings also go into the same volumetric flask, until the liquid level in the volumetric flask reaches the graduation line. Use a pipette to take solution 20mL from the volumetric flask and inject it into a 50mL conical flask. Add 3 drops of phenolphthalein indicator solution, and titrate with c(KOH)=0.025mol/L potassium hydroxide standard titration solution until a light red color appears.
• 7.1.4 When determining the water-soluble acid content after oxidation (non-volatile or volatile) for each sample, use the mildly oxidized samples in two oxidation tubes for parallel determinations.
• Note: The apparatus used in the test procedures of 7.1.2 and 7.1.3 (such as conical flasks, separatory funnels, test tubes, etc.) must all be pre-washed with distilled water, and the wash water checked with methyl orange indicator solution and phenolphthalein indicator solution must show a neutral reaction.

8.2 Determination of the sediment content and acid value formed after deep oxidation of lubricating oil

• 7.2.1 Deep oxidation of lubricating oil: weigh sample 30g into a clean, dry oxidation tube, accurate to 0.1g. Place a copper strip wound with a spiral wire into the sample, as shown in Figure 3. Then seal the mouth of the oxidation tube with a clean cork or cotton; the cork or cotton must be pre-washed with benzene and dried. The test apparatus is as shown in Figure 5: immerse the assembled oxidation tube in an oil bath heated to 125℃±0.5℃, allowing its spiral portion to be completely immersed in the oil bath (the liquid level in the bath should be higher than the liquid level in the tube). Then, continuously pass oxygen into the sample at a rate of 200mL per minute, and measure the flow rate with a flow meter. The oxidation operation is carried out continuously at 125℃±0.5℃ for 8h.
• 7.2.2 After oxidation is completed, remove the oxidation tube from the oil bath, cool to about 60℃, then with gentle blowing, stir the oxidized oil in the tube to make it uniform, then pour oxidized oil 20～25g into a 100mL graduated cylinder with a ground stopper, accurate to 0.01g, for the determination of sediment content and acid value. Dilute the oxidized oil in the graduated cylinder with three times its volume of refined gasoline, move it to a dark place at a temperature of 20℃±3℃ and let it stand for 12h, then determine the sediment content. If the saponification value of the oxidized oil needs to be determined, add oxidized oil 2～4g to a conical flask, accurate to 0.001g, and determine according to GB/T 8021. Note: ① The refined gasoline used for dissolving and washing each portion of oxidized oil requires a total of 150～200mL. ② When determining sediment content and acid value, the operations of weighing the oxidized oil and diluting with gasoline should be carried out immediately upon completion of oxidation.
• 7.2.3 Determination of sediment content: after standing for 12h, filter the mixture of oxidized oil and refined gasoline through filter paper into a 250mL graduated cylinder. Wash the sediment on the filter paper with refined gasoline, and the washing gasoline is also filtered into the same graduated cylinder, until the filtered gasoline is colorless. Dilute the filtrate to the graduation line, ready for acid value determination. Then, dissolve the sediment on the filter paper with freshly prepared warm ethanol-benzene mixture, and let the filtrate flow into a pre-weighed 50mL conical flask. Distill off the ethanol-benzene mixture in the conical flask on a water bath. Place the conical flask and sediment in an oven at 105℃±3℃ and dry to constant weight, that is, the difference between two consecutive weighing results is not greater than 0.0004g. Note: If the mixture of oxidized oil and gasoline has no sediment adhering to the inner wall of the graduated cylinder, the following procedure is permitted for determining sediment content: beforehand place the filter paper in a weighing bottle, dry in an oven at 105℃±3℃ to constant weight (when drying in the drying oven, the weighing bottle is left open), that is, the difference between two consecutive weighing results is not greater than 0.0004g. Then filter this mixture through the constant-weight filter paper into a 250mL graduated cylinder. The refined gasoline used to wash the sediment is also filtered into the same graduated cylinder, until the filtered gasoline is colorless. Thereafter, transfer the filter paper and sediment into the original weighing bottle, and dry at 105℃±3℃ to constant weight.
• 7.2.4 Determination of acid value: accurately measure 25mL of the oxidized oil and gasoline mixture in a graduated cylinder. Into a 250mL conical flask, add ethanol-benzene mixture 20～25mL and 20g/L alkaline blue 6B ethanol indicator solution 1～2 drops, and neutralize with c(KOH)=0.05mol/L potassium hydroxide ethanol standard titration solution. To the neutralized ethanol-benzene mixture, add oxidized oil and gasoline mixture 25mL and 20g/L alkaline blue 6B ethanol indicator solution 0.5mL, and titrate with c(KOH)=0.05mol/L potassium hydroxide ethanol standard titration solution until the blue color of the mixture disappears completely or turns light red, which is judged as the titration endpoint. For certain oils, when the color of the mixture undergoes a sudden change, it is judged as the titration endpoint.
• 7.2.5 Carry out a blank titration as described in 7.2.4, without adding the oxidized oil and gasoline mixture.
• 7.2.6 When determining the sediment content and acid value after oxidation for each sample, use the deeply oxidized samples in two oxidation tubes for duplicate determinations.

8.3 Cleaning of oxidation tubes and treatment of metal parts (preparatory work)

• 6.4 First wash the oxidation tube with cold ethanol-benzene mixture. Then place the mixture in the apparatus and boil for 15min, then pour it out, wash the oxidation tube successively with 95% ethanol and water, then wash several times with hot chromic acid cleaning solution, finally wash with sulfuric acid, and wash several times with water, rinse with distilled water, then blow dry with hot air or dry in an oven.
• 6.5 Wipe the copper strip and copper ball clean, wash with ethanol-benzene mixture, and after air drying, carry out reduction treatment: immerse the copper strip and copper ball in nitric acid-phosphoric acid mixed solution and shake for 5s, take them out, rinse with distilled water, and immediately place in methanol for later use. After carefully wiping the steel wire with emery cloth, the spiral wire wound from it should be immersed in boiling ethanol-benzene mixture for 15min, then washed with 95% ethanol, and then wiped dry with filter paper. The steel ball should also undergo the same treatment. Note: It is permitted to use the reduction treatment by heating the copper strip and copper ball in the oxidizing flame of a gas burner, then immersing them in methanol.

9. Qualitative and quantitative determination and calculation formulas

9.1 Non-volatile water-soluble acid content after oxidation X₁ (mgKOH/g) is calculated according to formula (1):

X₁ = (V − V₁/3) × c₁ × 0.0561 × 1.25 / 25 × n × 3 = 0.002805 (V − V₁) × n × c₁

• Where: V — the volume of potassium hydroxide standard titration solution consumed when titrating the mixture of water extract, mL;
• V₁ — the volume of potassium hydroxide standard titration solution consumed when titrating 60mL distilled water, mL;
• n — the number of portions of water extract;
• 3 — the ratio of 60mL to 20mL;
• c₁ — the actual concentration of the potassium hydroxide standard titration solution, mol/L;
• 0.0561 — the mass of acid (expressed as potassium hydroxide) in grams equivalent to 1.00mL potassium hydroxide standard titration solution [c(KOH)=1.000mol/L];
• 1.25 — the ratio of 25mL to 20mL;
• 25 — the mass of oxidized oil, g.
• Note: The original formula source-text extraction contains noise; the above is organized from the recognizable content of the source text, requires confirmation against the source standard (source-text extraction).

9.2 Volatile water-soluble acid content after oxidation X₂ (mgKOH/g) is calculated according to formula (2):

X₂ = (V₂ − V₁) × c₁ × 0.0561 × 1.25 / 30 = 0.002338 (V₂ − V₁) × c₁

• Where: V₁ — the volume of potassium hydroxide standard titration solution consumed when titrating 60mL distilled water, mL;
• V₂ — the volume of potassium hydroxide standard titration solution consumed when titrating 20mL of the test solution, mL;
• 3 — the ratio of 60mL to 20mL;
• c₁ — the actual concentration of the potassium hydroxide standard titration solution, mol/L;
• 0.0561 — the mass of acid (expressed as potassium hydroxide) in grams equivalent to 1.00mL potassium hydroxide standard titration solution [c(KOH)=1.000mol/L];
• 1.25 — the ratio of 25mL to 20mL;
• 30 — the mass of the sample, g.
• Note: The original formula source-text extraction contains noise; the above is organized from the recognizable content of the source text, requires confirmation against the source standard (source-text extraction).

9.3 Sediment content after oxidation X₃ [%(m/m)] is calculated according to formula (3):

X₃ = m₁ / M × 100

• In the formula: m₁ — mass of the precipitate, g;
• M — mass of the oxidized oil, g.

9.4 Acid value after oxidation X₄ (mgKOH/g) is calculated according to formula (4):

X₄ = (V₃ − V₀) × c₂ × 0.0561 × n₁ / m

• In the formula: V₃ — volume of potassium hydroxide-ethanol standard titration solution consumed during titration, mL;
• V₀ — volume of potassium hydroxide-ethanol standard titration solution consumed during blank titration, mL;
• c₂ — actual concentration of the potassium hydroxide-ethanol standard titration solution, mol/L;
• 0.0561 — mass of acid (expressed as potassium hydroxide) in grams equivalent to 1.00mL potassium hydroxide-ethanol standard titration solution [c(KOH)=1.000mol/L];
• n₁ — volume ratio of the entire gasoline solution to the solution used for titration;
• m — mass of the oxidized oil, g.

10. Precision

• Repeatability: the difference between two results of repeated determinations by the same operator shall not exceed the following value.
• The content of non-volatile water-soluble acids or the content of volatile water-soluble acids is 0.002mgKOH/g.
• The precipitate and acid value of the oxidized oil are 5% of the arithmetic mean.

11. Report

For the content of non-volatile water-soluble acids, the content of volatile water-soluble acids, the precipitate content, and the acid value of the sample after oxidation, the arithmetic mean of two results of repeated determinations shall be taken as the determination result.

12. Normative references

• GB/T 8021 Petroleum products — Determination of saponification number
• SH 0004 Solvent naphtha for the rubber industry (the original text source-text extraction is “SH OOC”, 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