SH/T 0296-1992 Determination of phosphorus content in additives and additive-containing lubricating oils (colorimetric method)

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Card type: Test method

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

• Standard number: SH/T 0296-92
• Chinese full title: Determination of phosphorus content in additives and additive-containing lubricating oils (colorimetric method)
• English name: not provided in the available source
• Replacement relationship: replaces SY 2676-82
• First issued: 1977 year (see additional notes)
• Approval/implementation: approved by China Petrochemical Corporation 1992-05-20, implemented on 1992-05-20

2. Scope of application and non-applicability

• Scope of application: This standard specifies a method for determining the phosphorus content in additives and additive-containing lubricating oils; it is applicable to additives and additive-containing lubricating oils.
• Not applicable: not provided in the available source.

3. Method principle

At high temperature, using zinc oxide as a capture agent, the phosphorus in the sample is converted into phosphorus pentoxide and retained in the zinc oxide. Then the zinc oxide is dissolved with nitric acid, converting the phosphorus pentoxide into phosphate radicals. Within a certain acidity range, the phosphate radicals form a stable yellow complex with ammonium vanadate-ammonium molybdate, and colorimetric measurement is carried out at a wavelength of 460nm.

4. Reagents and materials (purity / preparation)

4.1 Reagents (Chapter 4)

• 4.1 Potassium dihydrogen phosphate: analytical reagent.
• 4.2 Nitric acid: analytical reagent, concentration 65%~68% (m/m).
• 4.3 Zinc oxide: analytical reagent, powdered.
• 4.4 Ammonium metavanadate: analytical reagent.
• 4.5 Ammonium molybdate: analytical reagent.

4.2 Solution preparation (Chapter 5)

• 5.1 2.5g/L Ammonium vanadate solution: weigh 2.5g ammonium metavanadate, dissolve it in about 300mL distilled water under heating, after cooling add 20mL nitric acid [65%~68% (m/m)], transfer to a 1L volumetric flask, dilute to the mark with distilled water, and shake well.
• 5.2 50g/L Ammonium molybdate solution: weigh 50g ammonium molybdate into a 600mL beaker, add about 300mL distilled water, heat to dissolve (temperature not exceeding 60°C), after cooling transfer to a 1L volumetric flask, dilute to the mark with distilled water, and shake well (if precipitate appears, filter it).
• 5.3 0.1mg/mL Phosphorus standard solution: weigh 0.4393g potassium dihydrogen phosphate, dissolve it in a small amount of distilled water, transfer to a 1L volumetric flask, dilute to the mark with distilled water, and shake well.

4.3 Materials (3.2)

• 3.2.1 Quantitative filter paper.
• 3.2.2 Coordinate paper.

5. Instruments and equipment

• 3.1.1 72 type spectrophotometer or other colorimeter.
• 3.1.2 Porcelain crucible: 30mL, tall form.
• 3.1.3 Beaker: 100, 600mL.
• 3.1.4 Volumetric flask: 100mL.
• 3.1.5 Burette: 5, 50mL (original text reads “50nl”, requires confirmation against the source standard (source-text extraction)).
• 3.1.6 Triangular funnel.
• 3.1.7 Electric furnace.
• 3.1.8 Platform scale: sensitivity 0.1g.
• 3.1.9 Balance: sensitivity 0.1mg or 0.01mg.
• 3.1.10 High-temperature furnace: capable of heating to a constant 800±25°C. Equipped with a thermocouple and a millivolt meter with a scale of 1000°C and a division not greater than 25°C (the original text “constant 800 ± 25°C” “1000C” is source-text extraction noise, requires confirmation against the source standard (source-text extraction)).
• 3.1.11 Wash bottle.

6. Recommended operating conditions

• Ignition temperature: 800°C (high-temperature furnace 800±25°C).
• Ignition time: 10min.
• Colorimetric wavelength: 460nm.
• Color development standing time: 10min.
• Reference solution: blank.
• Working curve calibration period: calibrate once a quarter.

7. Sampling and sample preparation

• 6.1 On a rectangular filter paper piece with a side length of about 1.2cm (fold the two sides downward), weigh a sample approximately equivalent to 1mg phosphorus, accurate to 0.0002g, then place the filter paper flat on the bottom of the crucible.
• If the sample is oil, directly weigh in the crucible a sample approximately equivalent to 1mg phosphorus, accurate to 0.0002g.
• Weigh 4g zinc oxide, accurate to 0.1g, cover it on the sample, shake tightly, and make the surface of the zinc oxide layer flat.
• Take another crucible, place only 4g zinc oxide, accurate to 0.1g, as a blank test.

8. Analytical procedure

8.1 Working curve plotting (5.4)

Take nine 100mL volumetric flasks, add from a burette respectively 10mL 2.5g/L ammonium vanadate solution and 10mL 50g/L ammonium molybdate solution, shake well and set aside. Weigh nine portions of zinc oxide 4g (accurate to 0.1g), place them respectively in crucibles, ignite in a 800°C high-temperature furnace for 10min, take out, cool for about 3min, moisten the zinc oxide with distilled water, then add 10mL nitric acid from a burette, stir with a glass rod to dissolve all the zinc oxide, and transfer to the above reserved volumetric flasks. Then respectively add 0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0, 16.0mL phosphorus standard solution, dilute to the mark with distilled water, shake well, and let stand for 10min. Carry out colorimetric measurement at a wavelength of 460nm, using the blank as the reference solution, measure the absorbance, and plot the working curve with phosphorus content as the abscissa and absorbance as the ordinate (the working curve must be calibrated once a quarter).

8.2 Test procedure (Chapter 6)

• 6.2 Place the crucibles containing the sample and the blank test simultaneously in a 800°C high-temperature furnace and ignite for 10min (if the sample is oil, first cover all the zinc oxide with a conical filter paper cap with an ignition wick at the top, then place it on an electric furnace and heat at high temperature until a large amount of oil smoke emerges, ignite the filter paper cap, and after the oil smoke burns out and the flame goes out, transfer it to the high-temperature furnace), take out after about 3min, moisten all the zinc oxide with distilled water, then add 10mL nitric acid from a burette, and stir with a glass rod to dissolve all the zinc oxide.
• 6.3 Add from a burette 10mL 2.5g/L ammonium vanadate solution and 10mL 50g/L ammonium molybdate solution into a 100mL volumetric flask, and shake well. Then transfer the solution in the crucible into the volumetric flask (if precipitate appears in the crucible, filter it), wash the crucible with distilled water, combine the washings into the volumetric flask, dilute to the mark with distilled water, and shake well. After standing for 10min, carry out colorimetric measurement at a wavelength of 460nm, using the blank as the reference solution.
• 6.4 Use the measured absorbance of the sample colorimetric solution to look up the standard working curve, and the corresponding phosphorus content can be obtained (mg).

9. Qualitative and quantitative determination and calculation formula

The phosphorus content in the sample X [% (m/m)] is calculated according to the following formula:

X = (X₀ / m) × 100

or

X = K·E × 100

Where:

• X₀——the phosphorus content corresponding to the measured absorbance on the standard working curve, mg;
• m—— the mass of the sample, mg;
• K—— the average K value (slope) of the standard working curve;
• E—— the measured absorbance.

(Note: The original formula layout is “X=×100” and “X K•E×100”, the numerator term source-text extraction is missing, and according to the context and symbol explanations it is supplemented as X₀/m and K·E, requires confirmation against the source standard (source-text extraction).)

10. Precision

The difference between two results of repeated determinations shall not exceed the following values:

(Note: The original text “5” “3” does not indicate units; it is understood according to the table header unit % (m/m), requires confirmation against the source standard (source-text extraction).)

11. Report

Take the arithmetic mean of two results of repeated determinations as the phosphorus content of the sample.

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