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JC/T 1088-2021 English PDF

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JC/T 1088-2021: Methods for chemical analysis of granulated electric furnace phosphorous slag
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Basic data

Standard ID JC/T 1088-2021 (JC/T1088-2021)
Description (Translated English) Methods for chemical analysis of granulated electric furnace phosphorous slag
Sector / Industry Building Materials Industry Standard (Recommended)
Classification of Chinese Standard Q11
Word Count Estimation 13,116
Issuing agency(ies) Ministry of Industry and Information Technology
JC/T 1088-2008 BUILDING MATERIAL INDUSTRY STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS Registration number: 24205-2008 Methods for chemical analysis of granulated electric furnace phosphorus slag ISSUED ON: JUNE 16, 2008 IMPLEMENTED ON: DECEMBER 01, 2008 Issued by: National Development and Reform Commission of PRC

Table of Contents

Foreword ... 4  1 Scope ... 5  2 Normative references ... 5  3 Terms and definitions ... 5  4 Basic requirements of test ... 6  5 Reagents and materials ... 7  6 Instruments and equipment ... 12  7 Preparation of specimen ... 13  8 Determination of loss on ignition - Ignition reduction method ... 13  9 Determination of silica - Potassium fluorosilicate capacity method ... 14  10 Determination of ferric oxide - EDTA direct titration ... 14  11 Determination of aluminum oxide - EDTA direct titration ... 14  12 Determination of calcium oxide - Calcium carbonate back titration ... 14  13 Determination of magnesium oxide - Atomic absorption spectroscopy (reference method) ... 16  14 Determination of sulfur trioxide - Barium sulfate gravimetric method ... 16  15 Determination of potassium oxide and sodium oxide - Flame photometric method ... 16  16 Determination of phosphorus pentoxide - Ammonium phosphomolybdate colorimetric method ... 16  17 Determination of magnesium oxide - EDTA titration reduction (substitution) ... 17  18 Determination of fluoride ions - Ion selective electrode method ... 18  19 Determination of chloride ions - Phosphoric acid distillation - Mercury salt titration ... 18  20 Repeatability limits and reproducibility limits ... 19 

Foreword

The consistency between this standard and EN 196-2:2005 “Method of testing cement - Part 2: Chemical analysis of cement” and ASTM C114:2005 “Standard test methods for chemical analysis of hydraulic cement” is not equivalent. This standard was proposed by the China Building Materials Federation. This standard shall be under the jurisdiction of the National Cement Standardization Technical Committee (SAC/TC 184). Drafting organizations of this standard: China Building Materials Science Research Institute, China Building Materials Inspection and Certification Center. Main drafters of this standard: Yan Weizhi, Wang Ruihai, Wang Guanjie, Wen Yugang, Huang Xiaolou. This standard is the first release. Methods for chemical analysis of granulated electric furnace phosphorus slag

Scope

This standard specifies the benchmark method and substitution method for the method of chemical analysis of granulated electric furnace phosphorus slag. In case of dispute, the benchmark method shall prevail. This standard applies to the granulated electric furnace phosphorus slag used in the building materials industry and other materials designated to adopt this standard.

Normative References

The 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 176-2008 Methods for chemical analysis of cement GB/T 2007.1 General rules for the sampling and sample preparation of minerals in bulk - Sampling by manual method GB/T 6682 Water for analytical laboratory use - Specification and test methods

Terms and Definitions

The terms and definitions as established in the GB/T 15000 series as well as the following terms and definitions apply to this standard. 3.1 Repeatability conditions The conditions for independent test of the same tested object in the same laboratory, by the same operator using the equipment, according to the same test method, in a short period of time. 3.2 Reproducibility conditions The conditions for independent test of the same tested object in different laboratories, by different operators using different equipment, according to the same test method. 3.3 Repeatability limit A value, under the repeatability conditions (3.1), the probability that the absolute difference between the two test results is less than or equal to this value is 95%. 3.4 Reproducibility limit A value, under reproducibility conditions (3.2), the probability that the absolute difference between the two test results is less than or equal to this value is 95%. 4 Basic requirements of test 4.1 Number of tests and requirements The number of tests per determination is specified as two. Use the average value of the two tests to express the determination result. Before the analysis, the specimen shall be baked at 105 °C ~ 110 °C for 2 h, cooled to room temperature in a desiccator, then weighed. In the chemical analysis, unless otherwise stated, it must determine the loss on ignition at the same time. For other determinations, it shall carry out the blank test at the same time, meanwhile correct the test results. 4.2 Expression of mass, volume, results Use “grams (g)” to express mass, accurate to 0.0001 g. The burette’s volume is expressed in “milliliter (mL)”, accurate to 0.05 mL. The unit of titer is expressed in “milligram per milliliter (mg/mL)”. The titer of chloride ions in the standard titration solution of mercury nitrate retains three significant digits after the rounding off. The titer and volume ratio of other standard titration solutions retain four significant digits after the rounding off. Unless otherwise stated, the results of each analysis are based on mass fraction. The analytical results of the chloride ion are expressed in % to three decimal places. The analytical results of other items are expressed in % to two decimal places. 4.3 Blank test Use the same amount of reagent. Do not add specimen. Use the same determination procedures to carry out test, to correct the determination results as obtained. 4.4 Ignition Place the filter paper and the precipitate in a crucible which has previously been burned to a constant weight. To avoid producing flame, in an oxidizing atmosphere, slowly dry and ash it. After ashing it to the absence of black carbon particle, then place it in a high-temperature furnace (6.4), to burn it at the specified temperature. In a desiccator (6.3), cool it to room temperature. Weigh it. 4.5 Constant weight After the first burning, cooling, weighing, use the method of applying continuous burning of 15 min, cooling, weighing, to check the constant mass. When the difference between two consecutive weighing results is less than 0.0005 g, it reaches constant weight. 5 Reagents and materials Unless otherwise stated, the reagents used shall be not less than analytical pure. The water used shall meet the requirements for grade-3 water as specified in GB/T 6682. The density of commercially available concentrated liquid reagents as listed in this standard refers to a density (ρ) at 20 °C, in grams per cubic centimeter (g/cm3). In chemical analysis, the acid or ammonia used, unless otherwise the concentration is not indicated, refers to commercially available concentrated acid or concentrated ammonia. Use the volume ratio to indicate the degree of dilution of the reagent. For example, hydrochloric acid (1 + 2) means that 1 part by volume of concentrated hydrochloric acid is mixed with 2 parts by volume of water. 5.1 Hydrochloric acid (HCI) 1.18 g/cm3 ~ 1.19 g/cm3, mass fraction 36% ~ 38%. 5.2 Hydrofluoric acid (HF) 1.15 g/cm3 ~ 1.18 g/cm3, mass fraction 40%. 5.3 Sulfuric acid (H2SO4) 1.84 g/cm3, mass fraction 95% ~ 98%. 5.4 Triethanolamine [N(CH2CH2OH)3] 1.12 g/cm3, mass fraction 99%. 5.5 Hydrochloric acid (1 + 1); (1 + 10) 5.6 Sulfuric acid (1 + 1) 5.7 Triethanolamine (1 + 2) 5.8 Sodium hydroxide (NaOH) 5.9 Anhydrous sodium carbonate Use an agate mortar to grind the anhydrous sodium carbonate (Na2CO3) finely ground to a powder form. 5.10 Sodium carbonate-borax mixed flux (2 + 1) Mix 2 parts by mass of anhydrous sodium carbonate (Na2CO3) and 1 part by mass of anhydrous borax (Na2B4O7) uniformly and grind it finely. Store it in a sealed bottle. 5.11 Sodium hydroxide solution (200 g/L) Dissolve 20 g of sodium hydroxide (NaOH) in water. Add water to dilute it to 100 mL. Store in plastic bottles. 5.12 Potassium hydroxide solution (200 g/L) Dissolve 200 g of potassium hydroxide (KOH) in water. Add water to dilute it to 1 L. Store in plastic bottles. 5.13 Ammonium molybdate solution (15 g/L) Dissolve 3 g of ammonium molybdate [(NH4)6Mo7O24 • 4H2O) in 100 mL of hot water. Add 60 mL of sulfuric acid (1 + 1) and shake it uniformly. After cooling, add water to dilute it to 200 mL. Store the solution in a plastic bottle. This solution is used within one week. 5.14 Ascorbic acid solution (50 g/L) Dissolve 5 g of ascorbic acid (V.C) in 100 mL of water. If necessary, filter it before use. Prepare it before use. 5.15 pH10 buffer solution Dissolve 67.5 g of ammonium chloride (NH4Cl) in water. Add 570 mL of ammonia water (NH3 • H2O). Add water to dilute it to 1 L. 5.16 Sodium potassium tartrate solution (100 g/L) Dissolve 10 g of sodium potassium tartrate (C4H4KNaO6 • 4H2O) in water. Add water to dilute it to 100 mL. 5.17 Potassium fluoride dissolution (20 g/L) Dissolve 20 g of potassium fluoride (KF • 2H2O) in water. Add water to dilute it to 1 L. Store it in a plastic bottle. 5.18 Preparation of phosphorus pentoxide (P2O5) standard solution 5.18.1 Preparation of phosphorus pentoxide standard solution Weigh 0.1917 g of potassium dihydrogen phosphate (KH2PO4, reference reagent) which has been baked at 105 °C ~ 110 °C for 2 h, accurate to 0.0001 g. Place it in a 300 mL beaker. Add water to dissolve it. Transfer it in a 1000 mL volumetric flask. Use water to dilute it to the mark. Shake it uniformly. Each milliliter of this standard solution contains 0.1 mg of phosphorus pentoxide. Pipette 50.00 mL of the above standard solution into a 500 mL volumetric flask. Use water to dilute it to the mark. Shake it uniformly. Each milliliter of this standard solution contains 0.01 mg of phosphorus pentoxide. 5.18.2 Drawing of working curve Pipette 0 mL, 2.00 mL, 4.00 mL, 6.00 mL, 8.00 mL, 10.00 mL, 15.00 mL, 20.00 mL, 25.00 mL of standard solution which contains 0.01 mg of phosphorus pentoxide per ml into a 200 mL beaker. Add water to dilute it to 50 mL. Add 10 mL of ammonium molybdate solution (5.13) and 2 mL of ascorbic acid solution (5.14). Heat to slightly boil it for (1.5 ± 0.5) min. After cooling it to room temperature, transfer it in a 100 mL volumetric flask. Use hydrochloric acid (1 + 10) to rinse the beaker. Use hydrochloric acid (1 + 10) to dilute it to the mark. Shake it uniformly. Use a spectrophotometer and 10 mm cuvette to determine the absorbance of the solution at a wavelength of 730 nm, which uses water as a reference. Use the determined absorbance as a function of the corresponding phosphorus pentoxide content, to draw the working curve. 5.19 Calcium carbonate standard solution [c(CaCO3) = 0.024 mol/L] Weigh 0.6 g (m1) of calcium carbonate (CaCO3, reference reagent) which has been baked at 105 °C ~ 110 °C for 2 h, accurate to 0.0001 g. Place it in a 400 mL beaker. Add about 100 mL of water. Cover the watch glass. Slowly add 5 mL ~ 10 mL of hydrochloric acid (1 + 1) along the mouth of the beaker. Stir it until all the calcium carbonate is dissolved. Heat the solution to boil. Cool it to room temperature. Transfer it in a 250 mL volumetric flask. Use water to dilute it to the mark. Shake it uniformly. 5.20 EDTA standard titration solution [c(EDTA) = 0.015 mol/L] 5.20.1 Preparation of EDTA standard titration solution Weigh about 5.6 g of EDTA (ethylene diamine tetraacetic acid, C10H14N2O8Na2 • CHO) in a beaker. Add about 200 mL of water. Heat it to dissolve it. Filter it. Add water to dilute it to 1 L. Shake it uniformly. 5.20.2 Calibration of EDTA standard titration solution’s concentration Pipette 25.00 mL of calcium carbonate standard solution (5.19) into a 400 mL beaker. Add water to dilute it to about 200 mL. Add appropriate amount of CMP mixing indicator (5.22). Whilst stirring it, add potassium hydroxide solution (5.12) until green fluorescence appears. Add another 2 mL ~ 3 mL. Use EDTA standard titration solution to titrate it until the green fluorescence disappears and red appears. The concentration of the EDTA standard titration solution is calculated according to formula (1): Where: c(EDTA) - The concentration of the EDTA standard titration solution, in moles per liter (mol/L); V1 - The volume of the EDTA standard titration solution as consumed in titration, in milliliters (mL); m1 - The mass of calcium carbonate in the calcium carbonate standard solution as prepared in accordance with 5.19, in grams (g); 100.09 - The molar mass of CaCO3, in grams per mole (g/mol). 5.20.3 Calculation of titration of each oxide by EDTA standard titration solution The titer of EDTA standard titration solution for ferric oxide, aluminum oxide, calcium oxide, magnesium oxide is calculated according to formula (2), formula (3), formula (4), formula (5), respectively: Where: TFe2O3 - The titer of EDTA standard titration solution for ferric oxide, in milligrams per milliliter (mg/mL); TAl2O3 - The titer of EDTA standard titration solution for aluminum oxide, in milligrams per milliliter (mg/mL); TCaO - The titer of EDTA standard titration solution for calcium oxide, in milligrams per milliliter (mg/mL); TMgO - The titer of EDTA standard titration solution for magnesium oxide, in milligrams per milliliter (mg/mL); c(EDTA) - The concentration of the EDTA standard titration solution, in moles per liter (mol/L); 79.84 - The molar mass of (1/2Fe2O3), in grams per mole (g/mol); 50.98 - The molar mass of (1/2Al2O3), in grams per mole (g/mol); 56.08 - The molar mass of CaO, in grams per mole (g/mol); 40.31 - The molar mass of MgO, in grams per mole (g/mol). 5.21 Calcium carbonate standard titration solution [c(CaCO3) = 0.015 mol/L] 5.21.1 Preparation of standard titration solution Weigh 1.50 g of calcium carbonate (CaCO3) which has been baked at 105 °C ~ 110 °C for 2 h. Place it in a 400 mL beaker. Add about 200 mL of water. Cover the watch glass. Slowly add 5 mL ~ 10 mL of hydrochloric acid (1 + 1) along the mouth of beaker. Stir it until all the calcium carbonate is dissolved. Heat to boil it for several minutes. Cool the solution to room temperature. Transfer it into a 1000 mL volumetric flask. Use water to dilute it to the mark. Shake it uniformly. 5.21.2 Calibration of volume ratio of EDTA standard titration solution to calcium carbonate standard titration solution Slowly release 10 mL ~ 15 mL EDTA standard titration solution (5.20) from the burette into a 400 mL beaker. Add about 200 mL of water. Add appropriate amount of CMP mixing indicator (5.22). Whilst stirring it, add potassium hydroxide solution (5.12) until a stable red color appears. Add another 2 mL ~ 3 mL. Use calcium carbonate standard titration solution (5.21.1) to titrate it until a green fluorescence appears. The volume ratio of the EDTA standard titration solution to the calcium carbonate standard titration solution is calculated according to formula (6): Where: K1 - The volume ratio of EDTA standard titration solution to calcium carbonate standard titration solution; V2 - The volume of the EDTA standard titration solution, in milliliters (mL); V3 - The volume of the calcium carbonate standard titration solution as consumed in titration, in milliliters (mL). 5.22 Calcein - methyl thymol blue - phenolphthalein mixed indicator (shortly referred to as CMP mixed indicator) Weigh 1.000 g of calcein, 1.000 g of methyl thymol blue, 0.200 g of phenolphthalein, 50 g of potassium nitrate (KNO3) which has been dried at 105 °C ~ 110 °C. Mix and grind it fine. Store it in a mouth-grinding bottle. 5.23 Acid chrome blue K - naphthol green B mixed indicator (shortly referred to as KB mixed indicator) Weigh 1.000 g of acid chrome blue K, 2.500 g of naphthol green B, 50 g of potassium nitrate (KNO3) which has been dried at 105 °C ~ 110 °C. Mix and grind it fine. Store it in a mouth-grinding bottle. 5.24 P-nitrophenol indicator solution (2 g/L) Dissolve 0.2 g of p-nitrophenol in 100 mL of water. 6 Instruments and equipment 6.1 Balance It shall not be lower than grade-4, accurate to 0.0001 g. 6.2 Platinum, silver, porcelain crucible It has a lid. The capacity is 15 mL ~ 30 mL. 6.3 Dryer It is loaded with color-changing silica gel. 6.4 High-temperature furnace For the flame-isolated heating furnace, carry out resistance heating on the periphery of the furnace. It shall use temperature controller to accurately control the furnace’s temperature. The controllable temperature is (950 ± 25) °C. 6.5 Glass capacity vessel Burette, volumetric flask, pipette. 6.6 Spectrophotometer It can, within the range of 400 nm ~ 800 nm, determine the absorbance of the solution. It is equipped with a 10 mm cuvette. 7 Preparation of specimen Use the method of GB/T 2007.1 to take sample. The samples as sent to the lab shall be representative uniform samples. Use quartering method or a reducer to reduce the specimen to about 100 g. Use a 80 μm square-hole sieve to sieve it. Use a magnet to remove the metal iron from the materials as left on the sieve. Grind the materials as left on the sieve to make it all pass a 80 μm square-hole sieve. Thoroughly mix it uniformly. Contain it in the sample bottle. Seal it for preservation, to prepare for determination. 8 Determination of loss on ignition - Ignition reduction method 8.1 Summary of method The specimen is burned in a high-temperature furnace at (950 ± 25) °C, to drive off carbon dioxide and moisture, while oxidizing the existing oxidizable elements. 8.2 Analytical procedures Weigh about 1 g of specimen (m2), accurate to 0.0001 g. Place it in a porcelain crucible which has been burned to constant weight. Place the lid inclined on the crucible. Place it in a high-temperature furnace (6.4). From low temperature, gradually increase the temperature. Burn it at (950 ± 25) °C for 15 min ~ 20 min. Remove the crucible to place it in a desiccator (6.3). Cool it to room temperature. Weigh it. Repeat burning, until reaching to constant weight. 8.3 Calculation and representation of results The mass fraction of the loss on ignition wLOI is calculated according to formula (7): Where: wLOI - The mass fraction of loss on ignition, %; m2 - The mass of sample, in grams (g); m3 - The mass of sample after burning, in grams (g). 9 Determination of silica - Potassium fluorosilicate capacity method It is carried out according to clause 23 of GB/T 176-2008. 10 Determination of ferric oxide - EDTA direct titration It is carried out according to clause 12 of GB/T 176-2008. 11 Determination of aluminum oxide - EDTA direct titration It is carried out according to clause 13 of GB/T 176-2008. 12 Determination of calcium oxide - Calcium carbonate back titration 12.1 Summary of method In a strong alkaline solution above pH13, use triethanolamine as a masking agent, use CMP mixed indicator, to add the excess EDTA standard titration solution for calcium. Use calcium carbonate standard titration solution to back titrate the excess EDTA dropwise. 12.2 Analytical procedures Weigh about 0.5 g of specimen (m4), accurate to 0.0001 g. Place it in the silver crucible. Add 6 g ~ 7 g of sodium hydroxide (5.8). Cover the lid (leave a gap). Place it in a high-temperature furnace (6.4). Starting from low temperature, melt it at a high-temperature of 650 °C ~ 700 °C for 20 min, during which time it is removed and shaken once. Remove to cool it. Place the crucible into a 300 mL beaker which contains about 100 mL of boiling water. Cover the watch glass. Heat it slightly on the electric furnace. After the frit is completely leached, remove the crucible. Use water to rinse the crucible and lid. Whilst stirring it, add 25 mL ~ 30 mL of hydrochloric acid in one time. Then add 1 mL of nitric acid. Use hot hydrochloric acid (1 + 5) to clean the crucible and lid. Heat the solution to boil it. After cooling it, transfer it into a 250 mL volumetric flask. Use water to dilute it to the mark. Shake it uniformly. This solution A is used for the determination of calcium oxide (12.2) and magnesium oxide (17.2). Pipette 25.00 mL of solution from the solution A into a 400 mL beaker. Add 7 mL ~ 10 mL of potassium fluoride (5.17) solution. Add water to dilute it to about 200 mL. Add 5 mL of triethanolamine (1 + 2) and appropriate amount of CMP mixed indicator (5.22). Whilst stirring it, add potassium hydroxide solution (5.12), until green fluorescence appears. Add another 5 mL ~ 8 mL. Use the EDTA standard titration solution [c(EDTA) = 0.015 mol/L] (5.20) to titrate it, until the green fluorescence disappears and a stable red color appears. Add another 3 mL ~ 5 mL. Place it for 1 min. Then use calcium carbonate standard titration solution (5.21) to titrate it, until green fluorescence appears. 12.3 Calculation and representation of results The mass percentage of calcium oxide wCaO is calculated according to formula (8): Where: wCaO - The mass fraction of calcium oxide, %; TCaO - The titer of EDTA standard titration solution for calcium oxide, in milligrams per milliliter (mg/mL); V4 - The volume of EDTA standard titration solution added, in milliliters (mL); V5 - The volume of calcium carbonate standard titration solution as consumed by titration, in milliliters (mL); K1 - The volume ratio of EDTA standard titration solution to calcium carbonate standard titration solution; m4 - The mass of the sample in 12.2, in grams (g). 13 Determination of magnesium oxide - Atomic absorption spectroscopy (reference method) It is carried out according to clause 15 of GB/T 176-2008. 14 Determination of sulfur trioxide - Barium sulfate gravimetric method It is carried out according to clause 10 of GB/T 176-2008. 15 Determination of potassium oxide and sodium oxide - Flame photometric method It is carried out according to clause 17 of GB/T 176-2008. 16 Determination of phosphorus pentoxide - Ammonium phosphomolybdate colorimetric method 16.1 Summary of method In a certain acidic medium, phosphorus forms a blue complex with ammonium molybdate and ascorbic acid. Determine the absorbance of the solution at a wavelength of 730 nm. 16.2 Analytical procedures Weigh about 0.25 g of specimen (m5), accurate to 0.0001 g. Place it in a platinum crucible. Add a small amount of water to wet it, slowly add 3 mL of hydrochloric acid, 5 drops of sulfuric acid (1 + 1), 5 mL of hydrofluoric acid. Put it on the hot plate in the fume hood to slowly heat it. When it is almost dry, shake the crucible, to avoid splash loss. Evaporate it dry. Then add 3 mL of hydrochloric acid. Continuously place on the hot plate in the fume hood to evaporate it dry. After cooling, add 3 g of sodium carbonate-borax mixed flux (5.10) into the residue which is obtained by hydrofluoric acid treatment. Mix it uniformly. Melt it at 950 °C ~ 1000 °C for 10 min. Use the crucible tongs to hold the crucible to rotate it, to make the melt be uniformly attached to the inner wall of the crucible. After cooling, place the crucible in a 300 mL beaker which contains 10 mL of sulfuric acid (1 + 1) and 100 mL of water which had been heated to slightly boiling. Keep it in a slightly boiling state, until the melt is completely dissolved. Use water to rinse the crucible and lid. After cooling it, transfer it into a 250 mL volumetric flask. Use water to dilute it to the mark. Shake it uniformly. Pipette 10.00 mL of the above sample solution into a 200 mL beaker (the amount of sample solution is determined by the content of phosphorus pentoxide). Add water to 50 mL. Add 1 drop of p-nitrophenol indicator solution (5.24). Add sodium hydroxide solution (5.11) dropwise to yellow. Then add hydrochloric acid (1 + 1) dropwise to colorless. Add 10 mL of ammonium molybdate solution (5.13) and 2 mL of ascorbic acid (5.14). Heat to slightly boil it for (1.5 ± 0.5) min. After cooling, transfer it into a 100 mL volumetric flask. Use hydrochloric acid (1 + 10) to rinse the beaker. Use hydrochloric acid (1 + 10) to dilute it to the mark. Shake it uniformly. Use a spectrophotometer and 10 mm cuvette to determine the absorbance of the solution at a wavelength of 730 nm, using water as a reference. From the working curve (5.18.2), find the content of phosphorus pentoxide (m6). 16.3 Calculation and representation of results The mass percentage of phosphorus pentoxide wP2O5 is calculated according to formula (9): Where: wP2O5 - The mass fraction of phosphorus pentoxide, %; m6 - The content of phosphorus pentoxide in 100 mL solution, in milligrams (mg); m5 - The mass of the sample in 16.2 (m5), in grams (g). 17 Determination of magnesium oxide - EDTA titration reduction (substitution) 17.1 Summary of method In a solution of pH10, use triethanolamine, sodium potassium tartrate as a masking agent, use the acid chrome blue K-naphthol chloride B mixed indicator, use the EDTA standard titration solution for titration. 17.2 Analytical procedures Pipette 25.00 mL of solution from the solution A into a 400 mL beaker. Add water to dilute it to about 200 mL. Add 1 mL of sodium potassium tartrate (5.16) and 5 mL of triethanolamine (5.7). Stir it. Then add 25 mL of pH10 buffer solution (5.15) and an appropriate amount of acid chrome blue K-naphthol green B mixed indicator (5.23). Use EDTA standard titration [c (EDTA) = 0.015 mol/L] (5.20) to titrate it. When approaching the end point, it shall slowly titrate it to pure blue. 17.3 Representation of results The mass fraction of magnesium oxide, wMgO, is calculated according to formula (10): Where: wMgO - The mass fraction of magnesium oxide, %; TMgO - The titer of EDTA standard titration solution for magnesium oxide, in milligrams per milliliter (mg/mL); V6 - The volume of EDTA standard titration solution as consumed in titration of total calcium and magnesium, in milliliters (mL); m4 - The mass of the sample in 12.2, in gram (g); wCaO - The mass fraction of calcium oxide as determined by 12.2, %; 0.7188 - Conversion factor of calcium oxide to magnesium oxide. 18 Determination of fluoride ions - Ion selective electrode method It is carried out according to clause 37 of GB/T 176-2008. 19 Determination of chloride ions - Phosphoric acid distillation - Mercury salt titration It is carried out according to clause 35 of GB/T 176-2008. 20 Repeatability limits and reproducibility limits The repeatability limits and reproducibility limits as listed in this standard are absolute deviations, which are expressed as mass fraction (%). Under repeatability conditions (3.1), when using the methods as listed in this standard to analyze the same specimen, the difference between the two analytical results shall be within the listed repeatability limits (Table 1). If the repeatability limit is exceeded, it shall make the third determination in a short time. If the difference between the determination result and either of the previous two analytical results meets the requirements for repeatability limit, take the average. Otherwise, it shall find the causes and carry out analysis according the provisions above again. Under reproducibility conditions (3.2), when using the methods as listed in this standard to analyze each of the same specimen, the difference between the average values of the analytical results as obtained shall be within the listed reproducibility limits (Table 1). The repeatability limits and reproducibility limits of the chemical analysis methods are as shown in Table 1. Table 1 -- Repeatability limits and reproducibility limits of the determination results Component Determination method Repeatability limit (%) Reproducibility limit (%) Loss on ignition Burning reduction method 0.15 0.25 Silica Potassium fluorosilicate capacity method 0.20 0.30 Ferric oxide EDTA direct titration 0.15 0.20 Aluminum oxide EDTA direct titration 0.20 0.30 Calcium oxide EDTA back titration 0.25 0.40 Magnesium oxide (reference method) Atomic absorption spectrometry 0.15 0.25 Sulphur trioxide Barium sulfate gravimetric method 0.15 0.20 Potassium oxide Flame photometry 0.10 0.15 Sodium oxide Flame photometry 0.05 0.10 Phosphorus pentoxide Ammonium phosphomolybdate colorimetric method 0.15 0.20 Magnesium oxide EDTA titration reduction method 0.20 0.30 Fluoride ion Ion selective electrode method 0.05 0.10 Chloride ion Phosphoric acid distillation-mercury salt titration 0.003 0.005 __________ END __________

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