SH/T 0197-1992 Determination of Iron Content in Lubricating Oils

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Card type: Test method

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

• Standard number: SH/T 0197-92
• Full name: Determination of Iron Content in Lubricating Oils
• English name: not provided in the available source
• Replacement relationship: replaces LB E34 006-88
• Other: approved by 1992-05-20, implemented by 1992-05-20; (confirmed in 2004)
• Contains three methods: A method—colorimetric method, B method—gravimetric method, C method—volumetric method; for arbitration testing, the colorimetric method is used to determine iron content.

2. Scope of application and non-applicability

• This standard specifies three methods for determining iron content in lubricating oils: A method—colorimetric method, B method—gravimetric method, and C method—volumetric method. For arbitration testing, the colorimetric method is used to determine iron content.
• This standard applies to lubricating oils and used lubricating oils.
• Not applicable: not provided in the available source.

3. Method principle

• A method (colorimetric method): Burn and ash the sample, then dissolve it with dilute hydrochloric acid solution. Measure the absorbance of the sample solution diluted with distilled water using a spectrophotometer at 510nm, find the corresponding iron content from the working curve, and then calculate the iron content of the sample according to the formula.
• B method (gravimetric method): Burn and ash the sample, then dissolve it with dilute hydrochloric acid solution. Add nitric acid to the sample solution diluted with distilled water, and under heating add ammonia water; the flocculent precipitate of iron hydroxide is washed, calcined, and then weighed to constant weight. Calculate its iron content according to the formula.
• C method (volumetric method): Burn and ash the sample, then dissolve it with dilute hydrochloric acid solution. Add potassium iodide, titrate the liberated iodine with sodium thiosulfate standard titration solution, and calculate the iron content according to the formula.

4. Reagents and materials (purity / preparation)

A method

• 5.1 Anhydrous ethanol: analytical reagent.
• 5.2 Reagent name unclear in the source (source-text extraction; suspected phenanthroline, unverified): analytical reagent; the source specifies a 100g/L ethanol solution of this reagent. Verify the reagent identity before use.
• 5.3 Hydroxylamine hydrochloride (requires confirmation against the source standard (source-text extraction), suspected to be hydroxylamine hydrochloride): analytical reagent, prepare as 100g/L hydroxylamine (requires confirmation against the source standard (source-text extraction)) solution.
• 5.4 Anhydrous sodium acetate: analytical reagent, prepare as 300g/L sodium acetate solution.
• 5.5 Hydrochloric acid: analytical reagent, prepare as hydrochloric acid solution according to the volume ratio of hydrochloric acid to water of 1:1.
• 5.6 Sodium hydroxide: analytical reagent, prepare as 80g/L sodium hydroxide solution.
• 5.7 Congo red test paper.
• 5.8 Pure iron wire.
• 6.1 Preparation of iron standard solution: Weigh 0.1000g pure iron wire into a 100mL beaker, add 25mL hydrochloric acid solution, and heat to dissolve completely. Then transfer to a 1000mL volumetric flask, add 20mL hydrochloric acid solution, dilute to the mark with distilled water; the iron concentration of this solution is 100μg/mL (requires confirmation against the source standard (source-text extraction), the original text is “1001,[unreadable unit]ML”). Take 10mL of the above solution, place it in a 100mL volumetric flask, add 5mL hydrochloric acid solution, and dilute to the mark with distilled water. The iron concentration of this solution is 10μg/mL (requires confirmation against the source standard (source-text extraction), the original text is “l01eg/ML”).
• Note: The iron standard solution may also be replaced by the following solution: Accurately weigh 0.7022g ferric ammonium sulfate (II) hexahydrate [FeSO4·(NH4)2SO4·6H2O] (purity at least 99.5%), dissolve in 100mL distilled water containing 20mL sulfuric acid (density 1.84g/mL), dilute to 1L with distilled water. Take 100mL of the above solution, dilute to 1L. (requires confirmation against the source standard (source-text extraction), the original chemical formula and volume are unclear in the source text)

B method

• 12.1 Nitric acid: chemically pure.
• 12.2 Ammonia water: chemically pure, 25.0%～28.0%(m/m).
• 12.3 Silver nitrate: chemically pure, prepare as 100g/L solution.
• 12.4 Hydrochloric acid: chemically pure, prepare as hydrochloric acid solution according to the volume ratio of hydrochloric acid to water of 1:1.

C method

• 18.2 Material: carbon dioxide, in steel cylinders.
• 19.1 Potassium iodide: chemically pure.
• 19.2 Hydrochloric acid: chemically pure, prepare as 10%(m/m) solution.
• 19.3 Sodium hydroxide: chemically pure, prepare as 100g/L solution.
• 19.4 Sodium thiosulfate: chemically pure, prepare as c(Na2S2O3)=0.1mol/L sodium thiosulfate standard titration solution.
• 19.5 Phenolphthalein: prepare as 10g/L ethanol indicator solution.
• 19.6 Starch: freshly prepared 5g/L (requires confirmation against the source standard (source-text extraction), the original text is “5[unreadable unit]L”) indicator solution.

5. Instruments and equipment

A method

• 4.1 72 type spectrophotometer or other spectrophotometer with equivalent performance.
• 4.2 Cuvette: 1cm light path.
• 4.3 High-temperature furnace: capable of maintaining constant temperature at 775℃±25℃ and automatically controlled.
• 4.4 Volumetric flasks: 10, 25, 50, 100, 1000mL.
• 4.5 Dropper.
• 4.6 Microburette: 10mL, graduation 0.05mL.
• 4.7 Porcelain crucible: 50mL.
• 4.8 Pipettes: 2, 5mL.
• 4.9 Beaker: 100mL.
• 4.10 Graduated cylinders: 10, 25mL.
• 4.11 Conical flask: 50mL.

B method

• 11.1 Ash determination apparatus: same as GB/T 508.
• 11.2 Volumetric flask: 500mL.
• 11.3 Beakers: 100, 250mL.
• 11.4 Pipettes: 1, 2, 5, 10, 25mL.

C method

• 18.1.1 Ash determination apparatus: same as GB/T 508.
• 18.1.2 Volumetric flasks: 100, 500mL.
• 18.1.3 Stoppered conical flasks: 100, 250mL.
• 18.1.4 Pipettes: 1, 2, 5, 10, 25mL.
• 18.1.5 Microburette: 2mL.

6. Recommended operating conditions

• A method determination wavelength: 510nm.
• A method cuvette light path: 1cm.
• A method color development heating: heat in boiling water bath for 2min.
• A method reference solution: distilled water.
• B method precipitation heating temperature: 70～80℃.
• B method calcination temperature: 775℃±25℃; calcination time 1.5～2.0h.
• C method standing time: after adding potassium iodide, let stand for 20min.
• Other: not provided in the available source.

7. Sampling and sample preparation

• 6.2 Sample treatment: Weigh 10-20g homogeneous sample into a porcelain crucible (accurate to 0.1g), and carry out combustion and ashing according to GB/T 508. After cooling, add 10mL hydrochloric acid solution along the crucible wall with a dropper, place on an electric hot plate to heat and dissolve the ash, and concentrate to about 2mL; transfer all into a 25mL or 50mL volumetric flask, wash the crucible several times with distilled water, transfer the washings into the volumetric flask, dilute to the mark, and shake well thoroughly to obtain the sample solution.
• Note: For the solution used for colorimetry, take the upper clear liquid; if colorimetry is performed with precipitate, it will affect the absorbance.
• B method 13.1: same as clause 6.2.
• C method 20: same as clause 6.2.

8. Analysis procedure

A method

• 6.3 Preparation of working curve: In six 50mL conical flasks, accurately add with a microburette 0, 0.5, 1.0, 1.5, 2.0, 2.5mL of the iron standard solution prepared according to clause 6.1, adjust with 80g/L sodium hydroxide solution until Congo red test paper just turns red. Add 1mL sodium acetate solution, 1mL hydroxylamine hydrochloride solution, and 1mL phenanthroline ethanol solution, shake well, heat in a boiling water bath for 2min, cool to room temperature, quantitatively transfer to a 10 or 25mL volumetric flask, and dilute to the mark. Using a 1cm light path cuvette, with distilled water as reference solution, measure the absorbance at 510nm. Calculate the iron content X1 (μg/mL) of each point according to formula (1)).
• 7.1 Accurately measure 2 or 5mL of the sample solution prepared in clause 6.2 as the sample solution for color development, place in a 50mL conical flask, adjust with 80g/L sodium hydroxide solution until Congo red test paper just turns red, add 1mL sodium acetate solution, 1mL hydroxylamine hydrochloride solution, and 1mL phenanthroline ethanol solution, and shake well. Heat in boiling water for 2min, cool to room temperature, quantitatively transfer to a 10 or 25mL volumetric flask, dilute to the mark, and measure the absorbance at 510nm using a 1cm light path cuvette with distilled water as reference solution.
• 7.2 For colorimetry of the same batch of samples, a blank test shall be performed.
• 7.3 Subtract the absorbance of the blank test from the read absorbance, then find the corresponding iron content from the working curve, and calculate the iron content of the sample according to Chapter 8.

B method

• 13.2 Place the empty crucible in a high-temperature furnace at 775℃±25℃ for calcination, take it out, cool in air for 3min, then place in a desiccator to cool for 30min, and weigh (accurate to 0.0002g); repeat calcination, cooling, and weighing until the difference between consecutive weighings is not greater than 0.0004g.
• 14 Test procedure: Using a pipette, take sample solution 25mL from the volumetric flask and inject it into a 100 or 250mL beaker. Add nitric acid 0.5mL, heat to 70-80℃, and precipitate iron with ammonia water until a slight ammonia odor is present. When the precipitated ferric hydroxide forms a flocculent precipitate, filter the above hot solution, and wash the precipitate with hot distilled water until the wash liquid is free of chloride ions. After slight drying, transfer the precipitate together with the filter paper to a crucible of constant weight, calcine in a high-temperature furnace at 775℃±25℃ for 1.5-2.0h, remove and cool in air for 3min, then transfer to a desiccator to cool for 30min, and weigh (accurate to 0.0002g). Repeat the calcination, cooling, and weighing until the difference between consecutive weighings is not greater than 0.0004g.

C method

• 21 Test procedure: Using a pipette, take sample solution 10mL from the volumetric flask, add it to a stoppered conical flask of volume 100 or 250mL, add 2-3 drops of phenolphthalein indicator solution, then add 100g/L sodium hydroxide solution to neutralize, replace the air in the conical flask with carbon dioxide, add 10%(m/m) hydrochloric acid solution (to weak acidic reaction) and 2-3g potassium iodide to the conical flask, then stopper the conical flask with a ground stopper, shake carefully and let stand for 20min. While shaking continuously, titrate the liberated iodine with sodium thiosulfate standard titration solution. When the liquid in the conical flask appears pale yellow, add 3mL starch indicator solution, and continue titrating until the blue color disappears. Then replace the air in the conical flask with carbon dioxide again, and let the conical flask stand. If the blue color reappears, add 1-2g potassium iodide to the conical flask, and titrate the liberated iodine with sodium thiosulfate standard titration solution until the blue color does not appear within 30min. Record the total milliliters of sodium thiosulfate standard titration solution consumed in the titration (V6).

9. Qualitative and quantitative and calculation formulas

A method

• The iron content of each point on the working curve X1 (μg/mL) is calculated according to formula (1): X1 = c1·V1 / V2 Where: c1— iron standard solution concentration μg/mL; V1— iron standard solution volume, mL; V2— color development volumetric flask volume, mL.
• Using the absorbance measured for each iron standard solution, subtract the absorbance of the blank test, and plot the working curve of absorbance E versus iron content X1 using the resulting net absorbance.
• The iron content of the sample X(ppm) is calculated according to formula (2): X = C·V2 / (m·V1) (requires confirmation (source-text extraction), the original formula symbols and text description contain noise) Original description: C— the absorbance of the sample solution minus the absorbance of the blank test, and the corresponding iron content is found from the working curve (the original unit place is “[unreadable unit]mL”, requires confirmation (source-text extraction)); V2— the amount of solution used for colorimetric comparison after dilution, mL; V1— the total amount of sample solution, mL; m— the mass of the sample, g; V— the amount of sample solution used for the color development reaction, mL (the correspondence between the original symbols and the description contains source-text extraction noise, requires confirmation (source-text extraction)).

B method

• The iron content of the sample X(m/m) is calculated according to formula (3): X = (M1·V1·0.6994) / (25·m) (requires confirmation (source-text extraction), the original formula layout contains noise) Where: M1— mass of the calcined residue, g; V1— volume of the sample after dilution in the volumetric flask, mL; 0.6994— coefficient for converting ferric oxide to iron; 25— volume of sample solution taken from the volumetric flask for iron determination, mL; m— mass of the sample, g.

C method

• The iron content of the sample X(m/m) is calculated according to formula (4): X = (V6·V7·0.05585·C2) / (10·m) (requires confirmation (source-text extraction), the original formula layout contains noise) Where: V6— volume of sodium thiosulfate standard titration solution consumed in titrating the sample, mL; V7— volume of the sample after dilution in the volumetric flask, mL; C2— actual concentration of the sodium thiosulfate standard titration solution, mol/L; 0.05585— mass of iron in grams equivalent to 1.00mL sodium thiosulfate standard titration solution [c(Na2S2O3)=1.000mol/L]; m— mass of the sample, g; 10— volume of sample solution taken from the volumetric flask for iron determination, mL.

10. Precision

• A method 9 precision: repeatability: the difference between two results of repeated determinations by the same operator and the arithmetic mean shall not be greater than the following values.

  Iron content, ppm	Repeatability, ppm
  1～5	30% of the arithmetic mean
  >5～10	10% of the arithmetic mean
  >10	6.5% of the arithmetic mean

• B method 16 precision: repeatability: the difference between two results of repeated determinations by the same operator shall not be greater than 10% of the smaller result.
• C method 23 precision: repeatability: the difference between two results of repeated determinations by the same operator shall not be greater than 15% of the smaller result (the original is “[unreadable value]%”, requires confirmation (source-text extraction)).

11. Report

• 24 Report: For the colorimetric method, gravimetric method, and volumetric method, the arithmetic mean of two results of repeated determinations is taken as the determination result.

12. Referenced documents

• GB/T 508 Petroleum products ash determination method

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 reference