GB/T 7143-2025 (GB/T 7143-2010) PDF EnglishUS$335.00 · In stock · Download in 9 seconds
GB/T 7143-2010: Methods for chemical analysis of silica sand for foundry Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid GB/T 7143: Historical versions
Similar standardsGB/T 7143-2010: Methods for chemical analysis of silica sand for foundry---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT7143-2010GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 71.040.99 J 31 Replacing GB/T 7143-1986 Methods for chemical analysis of silica sand for foundry Issued on: SEPTEMBER 26, 2010 Implemented on: FEBRUARY 01, 2011 Issued by. General Administration of Quality Supervision, Inspection and Quarantine of PRC; National Standardization Administration. Table of ContentsForeword... 3 1 Scope... 4 2 Normative references... 4 3 Preparation of specimens... 4 4 Test method... 5 4.1 Determination of silicon dioxide content... 5 4.2 Determination of aluminum oxide, iron oxide, titanium oxide content... 10 4.3 Determination of calcium oxide, magnesium oxide, potassium oxide, sodium oxide content... 21 4.4 Determination of iron oxide, calcium oxide, magnesium oxide, potassium oxide, sodium oxide content by atomic absorption spectrophotometry... 28 4.5 Determination of acid consumption value... 31 Methods for chemical analysis of silica sand for foundry1 ScopeThis standard specifies the preparation and test methods of chemical analysis specimens of silica sand for foundry. This standard applies to the analysis of silicon dioxide, aluminum oxide, iron oxide, titanium oxide, calcium oxide, magnesium oxide, potassium oxide, sodium oxide content, acid consumption value of natural silica sand, selected quartz sand, artificial quartz sand for foundry. The parallel determination methods in this standard can be selected according to specific circumstances.2 Normative referencesThe provisions in following documents become the provisions of this Standard through reference in this Standard. For the dated references, the subsequent amendments (excluding corrections) or revisions do not apply to this Standard; however, parties who reach an agreement based on this Standard are encouraged to study if the latest versions of these documents are applicable. For undated references, the latest edition of the referenced document applies. GB/T 601 Chemical reagent - Preparations of reference titration solutions GB/T 603 Chemical reagent - Preparations of reagent solutions for use in test methods GB/T 2684 Test methods for foundry sands and molding mixtures GB/T 6682 Water for analytical laboratory use - Specification and test methods GB/T 8170 Rules of rounding off for numerical values and expression and judgement of limiting values3 Preparation of specimens3.1 The specimens must be representative and uniform, without any foreign impurities. 3.2 The specimens for acid consumption value determination are selected from the specimens and carried out in accordance with the provisions of GB/T 2684. 3.3 The specimens for determination of other indicators are reduced by quartering (if the particle size is too large, it shall be crushed to less than 0.8 mm first; the iron introduced during the crushing process shall be removed by a magnet before being reduced). Finally, about 20 g of specimen is obtained, which is ground until all of them pass through a 75 µm sieve (i.e., a 200-mesh sieve). Place the above specimen in a weighing bottle; dry at 105 °C ~ 110 °C for 2 h; then put it in a dryer; cool it and set it aside.4 Test methodUnless otherwise specified, the standard solutions, preparations, products used in the analysis are prepared in accordance with GB/T 601 and GB/T 603.Use reagents confirmed to be analytically pure and grade 3 water in accordance with GB/T 6682.The reagents used in the test, if the concentration is not specified, are the original concentration at the time of exit-factory. The test results are determined according to the rounded value comparison method in GB/T 8170. 4.1 Determination of silicon dioxide content 4.1.1 Determination of silicon dioxide content by hydrochloric acid primary dehydration weight-molybdenum blue absorptiometry 4.1.1.1 Principle The specimen is melted and decomposed with sodium carbonate; the sinter is dissolved with hydrochloric acid; the silicic acid is evaporated to dryness to dehydrate; hydrochloric acid is added to dissolve soluble salts, filtered and burned into silicon dioxide, then treated with hydrofluoric acid to make silicon escape in the form of silicon tetrafluoride. The difference in mass before and after hydrofluoric acid treatment is the amount of silicon dioxide in the precipitate; the amount of residual silicon dioxide in the filtrate is determined by molybdenum blue absorptiometry. The sum of the two is the content of silicon dioxide in the specimen. 4.1.1.2 Reagents and materials a) Anhydrous sodium carbonate; b) Hydrochloric acid; c) Hydrofluoric acid; d) Ethanol. 95%; 4.1.1.4 Analysis steps a) Preparation of test solution. Weigh 0.5 g of specimen (accurate to 0.0001 g); place in a platinum crucible; add 1.5 g of anhydrous sodium carbonate; mix with the specimen; add 0.5 g of anhydrous sodium carbonate to cover the surface; place in a high-temperature box-type resistance furnace; gradually heat from low temperature to 1000 °C ~ 1050 °C; keep at this temperature for 15 min ~ 20 min; clamp the platinum crucible with crucible tongs with platinum heads; rotate carefully to make the molten material evenly adhere to the inner wall of the platinum crucible; cool it; cover with a watch glass; add 20 mL of hydrochloric acid [4.1.1.2e)] to dissolve the molten block; place the platinum crucible in a water bath; heat until the carbonate is completely decomposed and no more bubbles are emitted; remove it; wash the watch glass with hot water; remove the watch glass; then place the platinum crucible in a water bath to evaporate to dryness; place in an electric oven and dry at 130 °C for 1 h. Cool it; add 5 mL of hydrochloric acid [4.1.1.2b)]; let it stand for 5 min; add about 20 mL of hot water; stir to dissolve the salts; add appropriate amount of filter paper pulp and stir; filter with medium-speed quantitative filter paper; collect the filtrate and washing liquid in a 250 mL volumetric flask; wash the platinum crucible wall and precipitate with hot hydrochloric acid [4.1.1.2 g)], until there is no iron ion (check with potassium thiocyanate solution); continue to wash with hot water, until there is no chloride ion (check with silver nitrate solution). Move the precipitate and filter paper into the platinum crucible together; add 2 drops of sulfuric acid to the precipitate; dry it at low temperature on an electric furnace; then move it into a high-temperature furnace; gradually increase the temperature to fully ash the filter paper; finally burn it at 1150 °C ~ 1200 °C for 1 h; cool to room temperature in a dryer; weigh it; burn repeatedly until constant weight (the difference between two burning weighing is ≤ 0.0002 g, which is constant weight). Wet the precipitate with water; add 3 drops of sulfuric acid and 5 mL ~ 7 mL of hydrofluoric acid; evaporate to dryness in a low-temperature furnace; repeat the process once; continue heating until all the sulfur trioxide smoke is gone; burn the crucible at 1150 °C ~ 1200 °C for 15 min; cool to room temperature in a desiccator; weigh it; burn repeatedly until constant weight (the difference between two burning weighing is ≤ 0.0002 g, which is constant weight). b) Determination of the specimen. Dilute the above filtrate with water to the mark; shake well; pipette 25 mL into a 100 mL plastic cup; add 5 mL of potassium fluoride solution; shake well; let it stand for 10 min; add 5 mL of boric acid solution; add 1 drop of p-nitrophenol For quartz sand specimens with a silicon dioxide content of more than 95%, after burning to constant weight, treat with nitric acid and hydrofluoric acid to make silicon escape in the form of silicon tetrafluoride; then burn to constant weight. The weight loss is the silicon dioxide content. 4.1.2.2 Reagents and materials a) Nitric acid; b) Hydrofluoric acid. 4.1.2.3 Instruments a) Analytical balance. Accuracy 0.0001 g; b) Platinum crucible. 30 mL ~ 100 mL; c) High temperature box resistance furnace. 4.1.2.4 Analysis steps Weigh about 1 g of specimen, accurate to 0.0001 g; place in a platinum crucible with constant weight (the difference between two burning weighing is ≤ 0.0002 g); put in a high-temperature furnace; gradually heat from low temperature to 950 °C ~ 1000 °C; keep warm for 1 h; take out and cool slightly; immediately put in a desiccator; cool to room temperature; weigh it. Repeat burning (15 min each time); weigh until constant weight (the difference between two burning weighing is ≤ 0.0002 g, which is constant weight). Moisten the specimen after burning with a few drops of water; add 5 mL of nitric acid and 5 mL ~ 8 mL of hydrofluoric acid; cover the crucible with a small gap; heat for 30 minutes without boiling on a low-temperature electric furnace (the test solution shall be clear at this time); wash the crucible cover with a small amount of water; continue heating and evaporating to dryness; remove it; cool it; add 5 mL of nitric acid and 5 mL of hydrofluoric acid; evaporate it again to dryness; then add 5 mL of nitric acid along the crucible wall; evaporate it again to dryness; treat it with nitric acid twice; finally raise the temperature until no nitrogen oxide is released. Move the platinum crucible into a high-temperature box-type resistance furnace; first at low temperature; then burn it at 1000 °C ~ 1050 °C for 30 minutes; take it out and place it in a desiccator; cool it to room temperature; weigh it; repeat the burning (burning for 15 minutes each time) until constant weight. Perform a blank test at the same time. 4.1.2.5 Result calculation Silicon dioxide content is expressed as mass fraction X2, the value is expressed in %, which is calculated according to formula (2). c) Chloroform; d) Potassium pyrosulfate; e) Hydrochloric acid. 1 + 1; f) Sulfuric acid. 1 + 1; g) Ammonia water. 1 + 1; h) Copper iron reagent solution. 10%, prepare it when needed, filter it before use; i) Acetic acid-ammonium acetate buffer solution (pH = 6.1). Take 300 g of ammonium acetate; dissolve it in 500 mL water; add 15 mL of glacial acetic acid; dilute it with water to 1000 mL; shake it well; j) Disodium ethylenediaminetetraacetic acid (EDTA) solution. 0.025 mol/L, weigh 9.3060 g of standard EDTA; dissolve it in 500 mL warm water; cool it; transfer it into a 1000 mL volumetric flask; dilute it with water to the mark; shake it well; k) Zinc standard solution. c(Zn) = 0.01000 mol/L, weigh 0.6538 g of metallic zinc (99.95% or more); add 10 mL of hydrochloric acid to a 250 mL beaker; heat to dissolve; cool it; transfer to a 1000 mL volumetric flask; add 2 ~ 3 drops of methyl orange indicator; slowly neutralize with ammonia until the solution just turns yellow; then adjust the solution from yellow to red with hydrochloric acid; add 5 ~ 6 drops in excess; dilute with water to the mark; shake well; l) Methyl orange indicator. 1 g/L; m) Xylenol orange indicator. 8 g/L. 4.2.1.1.3 Instruments a) Analytical balance. Accuracy 0.0001 g; b) Platinum crucible. 30 mL ~ 100 mL; c) High temperature box-type resistance furnace; d) Volumetric flask. 250 mL, Class A; e) Single-line pipette. 5 mL, 10 mL, 15 mL, 50 mL, Class A; f) Separatory funnel. 125mL, Class A; g) Burette. 50 mL, graduation value 0.1 mL, Class A. 4.2.1.1.4 Analysis steps g) Alumina standard solution. Weigh 0.1058 g of aluminum (content not less than 99.95%) into a plastic beaker; add 50 mL of sodium hydroxide solution (20%); heat and dissolve in a water bath; cool and add hydrochloric acid (1 + 1) dropwise, until it becomes acidic; add 20 mL in excess; heat in a water bath until the solution is clear; cool it; transfer to a 1000 mL volumetric flask; dilute to the mark with water; shake well; this solution is equivalent to 0.2 mg of aluminum oxide per milliliter. Transfer 25.00 mL of the above solution into a 1000 mL volumetric flask; add 20 mL of hydrochloric acid (1 + 1); dilute to the mark with water; shake well; this solution is equivalent to 0.005 mg of aluminum oxide per milliliter; h) Methyl orange indicator. 1 g/L; i) Chrome azure S solution. 0.5 g/L, prepared with ethanol (1 + 1). 4.2.1.2.3 Instruments a) Spectrophotometer; b) Single-marked pipettes. 5 mL, 10 mL, 20 mL, 25 mL, 50 mL, Class A; c) Volumetric flasks. 50 mL, 200 mL, 250 mL, 1000 mL, Class A. 4.2.1.2.4 Analysis steps a) Pipette 50 mL of test solution (A) into a 200 mL volumetric flask; dilute to the mark with water; shake well. b) According to the content of aluminum oxide in the specimen, pipette the above test solution into two 50 mL volumetric flasks as specified in Table 2, one as the color developing solution and the other as the reference solution. c) Color solution. Add 6 drops of hydrogen peroxide and 5 mL of zinc-EDTA solution; let it stand for 5 minutes; add 1 drop of methyl orange indicator; neutralize part of the acid with ammonia; carefully add ammonia until the solution just turns yellow; immediately add nitric acid until it turns red; add 5 mL in excess; shake well; let stand for a while; add 3 mL of chrome azurol blue S solution and 5 mL of hexamethylenetetramine solution; dilute to the mark with water; shake well; let stand for 20 minutes. d) Reference solution. Operate at the same time as the color solution, but before adding the chrome azurol blue S solution, add 5 drops of ammonium fluoride solution. e) Select an appropriate colorimetric dish according to the provisions of Table 2; measure the absorbance at a wavelength of 545 nm; find the corresponding amount of aluminum oxide from the working curve. method 4.2.2.1.1 Principle For specimens with an iron oxide content of 0.050% ~ 3.00%, in an ammonia medium, trivalent iron and sulfosalicylic acid form an orange-yellow complex; the absorbance is measured at a wavelength of 430 nm. 4.2.2.1.2 Reagents and materials a) Ammonia water. 1 + 1; b) Sulfosalicylic acid solution. 30%; c) Standard iron oxide solution. Accurately weigh 0.1000 g of standard iron oxide that has been pre-burned at 400 °C for 30 min and cooled to room temperature in a desiccator into a beaker; add 10 mL of hydrochloric acid (1 + 1); heat to dissolve; transfer to a 1000 mL volumetric flask after cooling; shake well. Each milliliter of this solution is equivalent to 0.1 mg of iron oxide. 4.2.2.1.3 Instruments a) Spectrophotometer; b) Single-line pipette. 10 mL, 20 mL, Class A; c) Volumetric flask. 100 mL, 1000 mL, Class A. 4.2.2.1.4 Analysis steps a) Determination of specimen. Pipette 10 mL of test solution (A) into a 100 mL volumetric flask; add 10 mL of sulfosalicylic acid solution; add 3 ~ 5 drops of ammonia water until it turns stable yellow; dilute with water to the mark; shake well; use the reagent blank as reference; select a 1 cm cuvette; measure the absorbance of the solution at 430 nm; find the amount of iron oxide from the working curve. b) Drawing of working curve. Pipette 0.00 mL, 1.00 mL, 2.00 mL, 4.00 mL, 6.00 mL, 8.00 mL, 10.00 mL, 12.00 mL of iron oxide standard solution into eight 100 mL volumetric flasks respectively; perform the following operations according to analysis step 4.2.2.1.4a); measure the absorbance; draw the working curve. 4.2.2.1.5 Result calculation The iron oxide content is expressed as mass fraction X5, the value is expressed in %, which is calculated according to formula (5). 4.3 Determination of calcium oxide, magnesium oxide, potassium oxide, sodium oxide content The specimen is decomposed with hydrofluoric acid-perchloric acid to remove silicon, evaporated with perchloric acid to remove fluoride; the residue is leached with dilute hydrochloric acid and diluted to a certain volume; the calcium oxide, magnesium oxide, potassium oxide and sodium oxide are determined by liquid separation. 4.3.1 Determination of calcium oxide content by EDTA complexometric titration 4.3.1.1 Principle For specimens with calcium oxide content above 0.10%, triethanolamine is used to mask interfering elements such as iron and aluminum. In a strong alkaline medium, calcein-thymolphthalein-acridine is used as a mixed indicator, calcium is directly titrated with EDTA standard solution. 4.3.1.2 Reagents and materials a) Hydrofluoric acid; b) Perchloric acid. 1 + 1; c) Hydrochloric acid. 1 + 11; d) Triethanolamine. 1 + 2; e) Potassium hydroxide solution. 30%, stored in a plastic bottle; f) Disodium ethylenediaminetetraacetic acid (EDTA) standard solution. c(EDTA) = 0.005 mol/L; weigh 1.86 g of EDTA in a 500 mL beaker; add about 200 mL of water; heat to dissolve; dilute to 1000 mL with water. g) Calcium oxide standard solution. 1 mg/mL, weigh 1.7848 g of high-purity calcium carbonate that has been dried at 105 °C ~ 110 °C for 2 h and cooled to room temperature in a desiccator; put it in a 300 mL beaker; add about 150 mL of water; add 10 mL of hydrochloric acid (1 + 1) to dissolve it; heat and boil for several minutes to drive away carbon dioxide; cool it; dilute it with water to 1000 mL; shake it well; this solution is equivalent to 1 mg calcium oxide per milliliter; h) Calcein-thymolphthalein-acridine mixed indicator. Weigh 0.2 g of calcein, 0.1 g of thymolphthalein, 0.4 g of acridine, 20 g of dried potassium sulfate; mix and grind well. 4.3.1.3 Instruments 4.3.2 Determination of magnesium oxide content by EDTA complexometric titration 4.3.2.1 Principle For specimens with magnesium oxide content above 0.10%, triethanolamine is used to mask interfering elements such as iron and aluminum. In an ammonia buffer medium, acid chrome blue K-naphthol green B is used as a mixed indicator. The total amount of calcium and magnesium is directly titrated with EDTA standard solution. The magnesium content is obtained by the difference between the total amount of calcium and magnesium and the calcium content. 4.3.2.2 Reagents and materials a) Ammonia. 1 + 1; b) Triethanolamine. 1 + 2; c) Ammonia-ammonium chloride buffer solution (pH = 10). Weigh 67.5 g of ammonium chloride; dissolve in 200 mL of water; add 570 mL of ammonia; dilute to 1000 mL with water; shake well; d) Disodium ethylenediaminetetraacetic acid (EDTA) standard solution. c(EDTA) = 0.005 mol/L; weigh 1.86 g of EDTA in a 500 mL beaker; add about 200 mL of water; heat to dissolve; dilute to 1000 mL with water; e) Acid chrome blue K-naphthol green B mixed indicator. 1 + 2; grind the mixed indicator and potassium nitrate in an agate mortar at a ratio of 1 + 50; store in a brown wide-mouth bottle. 4.3.2.3 Instruments a) Single-line pipette. 5 mL, 10 mL, 100 mL, Class A; b) Volumetric flask. 1000 mL, Class A; c) Conical flask. 300 mL; d) Burette. 50 mL, graduation value 0.1 mL, Class A. 4.3.2.4 Analysis steps Pipette 100 mL of specimen (B) (50 mL for specimens containing more than 1% magnesium oxide) into a 300 mL conical flask; add 5 mL of triethanolamine; dilute to 150 mL with water; add ammonia water to adjust the solution pH to about 10 (check with precision test paper); then add 10 mL of ammonia water-ammonium chloride buffer solution and appropriate amount of acid chrome blue K-naphthol green B mixed indicator; add EDTA standard solution until the test solution changes from purple-red equivalent to 1 mg of calcium oxide per milliliter; g) Magnesium oxide standard solution. 1 mg/mL; accurately weigh 1.0000 g of magnesium oxide that has been burned at 900 °C for 2 h and cooled to room temperature in a desiccator; place it in a 100 mL beaker; add 20 mL of hydrochloric acid; heat it to dissolve; cool it to room temperature; transfer it to a 1000 mL volumetric flask; dilute it to the mark with water; shake it well; store it in a dry plastic bottle. This solution is equivalent to 1 mg of magnesium oxide per milliliter; h) Iron oxide standard solution. 1 mg/mL; accurately weigh 1.0000 g of iron oxide that has been burned at 400 °C for 30 min and cooled to room temperature in a desiccator; place it in a 200 mL beaker; add 50 mL of hydrochloric acid; heat to dissolve; cool to room temperature; transfer to a 1000 mL volumetric flask; dilute to the mark with water; shake well; store in a dry plastic bottle. This solution is equivalent to 1 mg of iron oxide per milliliter; i) Potassium oxide standard solution. 1 mg/mL; accurately weigh 1.5830 g of potassium chloride that has been dried at 110 °C for 2 h and cooled to room temperature in a desiccator; place it in a 150 mL beaker; add water to dissolve; transfer to a 1000 mL volumetric flask; add 10 mL of hydrochloric acid; dilute to the mark with water; shake well; store in a dry plastic bottle. This solution is equivalent to 1 mg of potassium oxide per milliliter; j) Sodium oxide standard solution. 1 mg/mL; accurately weigh 110 °C dried for 2 h and cooled to room temperature in a desiccator; place it in a 150 mL beaker; add water to dissolve; transfer to a 1000 mL volumetric flask; add 10 mL of hydrochloric acid; dilute to the mark with water; shake well; store in a dry plastic bottle. This solution is equivalent to 1 mg of potassium oxide per milliliter; dry for 2 h; then cool to room temperature in a dryer. Place 1.8859 g of sodium chloride in a 150 mL beaker; dissolve it in water; transfer it to a 1000 mL volumetric flask; add 10 mL of hydrochloric acid; dilute with water to the mark; shake well; store in a dry plastic bottle. Each milliliter of this solution is equivalent to 1 mg of sodium oxide; k) Mixed standard solution. Pipette 50 mL of each of the above five standard solutions in a 1000 mL volumetric flask; add 10 mL of hydrochloric acid; dilute with water to the mark; shake well; set aside. The concentrations of iron oxide, calcium oxide, magnesium oxide, potassium oxide, sodium oxide in this mixed standard solution are all 50 μg/mL. Preparation of mixed standard series solutions. Use twelve 500 mL volumetric flasks to prepare a series of standard solutions according to the proportions in Table 14. ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. |
