SH/T 0309-1992 Determination of calcium, barium and zinc in additive-containing lubricating oils (complexometric titration method)

Summary page. This page is a compiled excerpt/summary of the standard — it is not the full standard text and does not replace it. Verify every value against the official standard and the product certificate before use.

SH/T 0309-1992 specifies a complexometric titration method for determining calcium, barium and zinc in unused lubricating oils containing additives, with sulfide, phosphorus and nitrogen reported as non-interfering.

Evidence note: the content of this page was compiled from the original text of this standard held in the Origin Standard library (points marked "[to be verified]" are "[source unclear]" in the original); for individual values and current status, refer to the original pages of the standard and the product certificate.

Scope: Applies to unused lubricating oils containing additives. The non-metal elements sulfur, phosphorus and nitrogen do not interfere with the determination. Determination ranges: zinc 0.02%–1.20% (m/m); calcium 0.03%–1.20% (m/m); barium 0.05%–3.00% (m/m). When calcium and barium are both present in the lubricating oil, the measurable calcium-to-barium ratio is 0.3–10, expressed as the amount of substance of barium to the amount of substance of calcium. The three coexisting elements calcium, barium and zinc may be determined simultaneously, or only any one or two of the elements to be determined may be determined. The method may also be used to determine the calcium, barium and zinc content in additives, but the sample mass taken shall be reduced as appropriate (the original character is misprinted and reads as "reduce alkali" instead of "reduce as appropriate", [to be verified] ([source unclear])). It does not apply to the determination of lubricating oils containing lead.

Principle: After the sample is diluted with toluene–n-butanol, calcium, barium and zinc in the sample are extracted with hydrochloric acid. In the extracted test solution at pH 5.5, the zinc content is determined using xylenol orange as indicator; the sample is treated with DDTC (sodium diethyldithiocarbamate) as precipitant to precipitate and remove zinc and any heavy metal elements present, then, with Eriochrome Black T as indicator, at pH 10, the total calcium and barium content is determined by back-titration with EDTA standard titration solution and magnesium chloride standard titration solution; the test solution, after adding DDTC and also a certain amount of potassium sulfate to remove zinc and barium, is used at pH greater than 13 with a calcium indicator to determine the calcium content. The difference between the total calcium and barium content and the calcium content is the barium content.

Apparatus: Pear-shaped separatory funnel: 300 mL. 3.1.2 Burette: 25 mL. 3.1.3 Volumetric flasks: 250 mL and 1 L. 3.1.4 Pipettes: 50 mL, 20 mL. 3.1.5 Shaker: fitted with a wooden rack for holding separatory funnels. 3.1.6 Conical flask: 250 mL. 3.1.7 Beakers: 100 mL, 250 mL. 3.2 Materials: filter paper: medium-speed qualitative filter paper, diameter 11 cm.

Reagents and reference materials: DDTC (sodium diethyldithiocarbamate): prepare a 50 g/L DDTC solution. 4.2 Hydrochloric acid: analytical grade, concentration 36%–38% (m/m). Prepare 19% (m/m) and 7% (m/m) hydrochloric acid solutions. 4.3 Sodium hydroxide: analytical grade, prepare a 100 g/L sodium hydroxide solution. 4.4 Ammonia water: analytical grade, ammonia content 25%–28% (m/m). Prepare a 4% (m/m) ammonia solution. 4.5 Toluene: analytical grade. 4.6 n-Butanol: analytical grade. 4.7 Sodium chloride: analytical grade. 4.8 Potassium sulfate: analytical grade, prepare a 20 g/L potassium sulfate solution. 4.9 Methyl orange indicator: prepare a 1 g/L methyl orange indicator solution. 4.10 Eriochrome Black T indicator: grind 1 g of Eriochrome Black T with 100 g of sodium chloride, then store in a ground-glass-stoppered bottle. 4.11 Xylenol orange indicator: grind 1 g of xylenol orange with 100 g of sodium chloride, then store in a ground-glass-stoppered bottle. 4.12 Zinc granules: arsenic-free primary standard reagent. 4.13 Malachite green indicator: prepare a 1 g/L ethanolic indicator solution. 4.14 Calcium indicator (C₂₁H₁₄N₂O₇S), also known as 2-hydroxy-1-(2-hydroxy-4-sulfo-1-naphthylazo)-3-naphthoic acid or calcon-carboxylic acid. Grind 1 g of calcium indicator with 100 g of sodium chloride, then store in a ground-glass-stoppered bottle. 4.15 Zinc oxide: primary standard reagent. 4.16 Other reagents: this standard also uses ammonium chloride, glacial acetic acid, anhydrous sodium acetate, magnesium chloride, anhydrous ethanol and other reagents. Unless specifically stated otherwise, all reagents used in this standard are of analytical grade.

Key conditions: pH for zinc determination: 5.5 (acetic acid–sodium acetate buffer solution). pH for total calcium and barium determination: 10 (ammonia–ammonium chloride buffer solution). pH for calcium determination: greater than 13 (adjusted with 100 g/L sodium hydroxide solution). Extraction: add 30 mL of 7% (m/m) hydrochloric acid solution and shake for 10 min. Washing: first wash the sample in the funnel once with about 40 mL of hot distilled water (70–80 °C), then wash the funnel once with 5 mL of 7% (m/m) hydrochloric acid solution and about 40 mL of hot distilled water, shaking for 5 min each time; then add 20 mL of hot distilled water and shake for 1 min. Heating temperature for precipitation separation: about 80 °C; cool for 40 min before filtering. Temperature of hot distilled water for washing the filter paper: 60–70 °C.

Calculation and results: Preparation of zinc chloride standard titration solution c(ZnCl₂)=0.015 mol/L: place about 5 g of zinc granules in a 100 mL beaker, add 20 mL of 19% (m/m) hydrochloric acid solution, allow to react for 3 min, then quickly wash off the residual acid with distilled water, wash twice more with anhydrous ethanol, dry in an oven at 105–110 °C for 10 min, remove and cool in a desiccator for 30 min, then accurately weigh 0.9807 g of the above zinc granules into a 1 L volumetric flask; tilt the flask at 45°, add 20 mL of 19% (m/m) hydrochloric acid solution, and after the zinc granules have completely reacted, dilute to the mark with distilled water. Formula (1): c(ZnCl₂) = 65.38 × 1 / m (the original is typeset as "65.38x1", [to be verified] ([source unclear])) where: m—mass of the zinc granules, g; 65.38—mass of 1 mol of zinc with the basic unit (Zn²⁺), g/mol; 1—volume of the zinc chloride solution, L. 5.2.2 Preparation of zinc oxide primary standard solution c(ZnO)=0.015 mol/L: weigh 1.221 g of primary standard zinc oxide ignited at 800 °C to constant mass, weighed to 0.0002 g. Dissolve in 5 mL of 19% (m/m) hydrochloric acid solution, transfer to a 1 L volumetric flask, dilute to the mark and mix well. Formula (2): c(ZnO) = 81.38 × 1 / m₂ (the original is typeset as "81.38x 1", [to be verified] ([source unclear])) where: m₂—mass of zinc oxide, g; 81.38—mass of 1 mol of zinc oxide with the basic unit (ZnO), g/mol; 1—volume of the zinc oxide primary standard solution, L. 5.3 Preparation of EDTA standard titration solution c(EDTA)=0.015 mol/L: weigh 5.6 g of disodium ethylenediaminetetraacetate and dissolve it in 1 L of distilled water with heating; after complete dissolution, mix well. Standardize with the above zinc chloride standard titration solution (5.2.1) or zinc oxide primary standard solution (5.2.2). For standardization, pipette 20 mL of the above solution (5.2.1 or 5.2.2) into a 250 mL conical flask, add 1 drop of methyl orange indicator solution, neutralize with 4% (m/m) ammonia solution until yellow, then adjust with 7% (m/m) hydrochloric acid solution until red, add 10 mL of pH 5.5 acetic acid–sodium acetate buffer solution and about 20 mg of xylenol orange indicator, and titrate with the EDTA solution to be standardized from red to yellow. Formula (3): c(EDTA) = c × 20 / V where: c—actual concentration of the zinc chloride standard titration solution (or zinc oxide primary standard solution), mol/L; 20—volume of the zinc chloride standard titration solution (or zinc oxide primary standard solution) taken, mL; V—volume of EDTA solution consumed in the titration, mL. 5.4 Preparation of magnesium chloride standard titration solution c(MgCl₂)=0.015 mol/L: weigh 3.1 g of magnesium chloride hexahydrate (MgCl₂·6H₂O), dissolve in distilled water and dilute to 1 L. Standardize with the above EDTA standard titration solution. For standardization, pipette 20 mL of EDTA standard titration solution into a 250 mL conical flask, add 1 drop of methyl orange indicator solution, neutralize with 4% (m/m) ammonia solution until just yellow, add 10 mL of pH 10 ammonia–ammonium chloride buffer solution and about 20 mg of Eriochrome Black T indicator, and titrate with the magnesium solution of concentration to be standardized until greyish purple. Formula (4): c(MgCl₂) = c(EDTA) × 20 / V₁ where: c(EDTA)—actual concentration of the EDTA standard titration solution, mol/L; V₁—volume of the magnesium chloride solution consumed in the titration, mL; 20—volume of EDTA standard titration solution taken, mL. 5.5 pH 5.5 acetic acid–sodium acetate buffer solution: take 200 g of anhydrous sodium acetate and 9 mL of glacial acetic acid, and dilute to 1 L with distilled water. 5.6 pH 10 ammonia–ammonium chloride buffer solution: take 570 mL of ammonia water, add 67 g of ammonium chloride, and dilute to 1 L with distilled water. 5.7 50 g/L DDTC solution: take 5 g of DDTC in a 250 mL beaker, add 95 mL of water, and dissolve with heating (do not boil). If insoluble matter is present, filter through medium-speed qualitative filter paper before use. 6.3.2 The zinc content X₁ [% (m/m)] in the sample is calculated according to formula (5): X₁ = c(EDTA) × V₁ × 0.06538 × 5 / m × 100 = c(EDTA) × V₁ × 32.69 / m where: c(EDTA)—actual concentration of the EDTA standard titration solution, mol/L; V₁—volume of the EDTA standard titration solution consumed in the titration, mL; m—mass of the sample, g; 0.06538—mass of zinc, in grams, equivalent to 1.00 mL of EDTA standard titration solution [c(EDTA)=1.000 mol/L]. 6.4.4 The calcium content X₂ [% (m/m)] in the sample is calculated according to formula (6): X₂ = c(EDTA) × V₂ × 0.0408 × 5 / m × 100 = c(EDTA) × V₂ × 20.04 / m where: c(EDTA)—actual concentration of the EDTA standard titration solution, mol/L; V₂—volume of the EDTA standard titration solution consumed in the titration, mL; m—mass of the sample, g; 0.0408—mass of calcium, in grams, equivalent to 1.00 mL of EDTA standard titration solution [c(EDTA)=1.000 mol/L]. 6.5.5 The barium content X₃ [% (m/m)] in the sample is calculated according to formula (7): X₃ = [c(EDTA) × (V₃ − V₂) − c(MgCl₂) × V₄] × 0.1374 × 5 / m × 100 = [c(EDTA) × (V₃ − V₂) − c(MgCl₂) × V₄] × 68.7 / m where: c(EDTA)—actual concentration of the EDTA standard titration solution, mol/L; V₃—volume of EDTA standard titration solution added, mL; V₂—volume of EDTA standard titration solution used in the calcium content determination in 6.4.3, mL; c(MgCl₂)—actual concentration of the magnesium chloride standard titration solution, mol/L; V₄—volume of the magnesium chloride standard titration solution consumed in the back-titration, mL; m—mass of the sample, g; 0.1374—mass of barium, in grams, equivalent to 1.00 mL of EDTA standard titration solution [c(EDTA)=1.000 mol/L].

Quality control: Judge the reliability of test results by the following provisions (95% confidence level). 7.1 Repeatability: the difference between two results obtained by the same operator in repeated determinations shall not exceed the values listed in Table 2. 7.2 Reproducibility: the difference between results submitted by two different laboratories shall not exceed the values listed in Table 2. Table 2 Precision: | Element | Content range, % (m/m) | Repeatability | Reproducibility | |---|---|---|---| | Zinc | ≤0.05 | 0.003 | 0.006 | | Zinc | >0.05–0.2 | 0.008 | 0.010 | | Zinc | >0.2–0.8 | 0.012 | 0.030 | | Zinc | >0.8–1.2 | 0.05 | 0.10 | | Calcium | ≤0.05 | 0.003 | 0.005 | | Calcium | >0.05–0.2 | 0.009 | 0.013 | | Calcium | >0.2–0.8 | 0.020 | 0.036 | | Calcium | >0.8–1.2 | 0.03 | 0.05 | | Barium | ≤0.05 | 0.015 | 0.020 | | Barium | >0.05–0.2 | 0.025 | 0.035 | | Barium | >0.2–0.8 | 0.04 | 0.09 | | Barium | >0.8–1.3 | 0.10 | 0.16 | | Barium | >1.3–3.2 | 0.13 | 0.36 |

Evidence note: [to be verified] and [source unclear] mark specific points that still require checking against the original text of the standard and do not indicate that they have been verified. Do not use these values or steps directly as a basis for work.

View public related products