Decision No. 03/2004/QD-BXD on the issuance of Vietnam Construction Standard TCXD VN 312:2004 Lime Rock - Chemical Analysis Method

DECISION OF THE MINISTER OF CONSTRUCTION

Regarding the issuance of the Vietnamese Construction Standard Male TCXD VN 312: 2004

Limestone - Methods of Chemical Analysis

 

THE MINISTER OF CONSTRUCTION

On the basis of  Decree No. 36/2003/ND-CP dated April 4, 2003 of the Government stipulates the functions, tasks, powers, and organizational structure of the Ministry of Construction.  Pursuant to the minutes of September 29, 2003

of the Inter-disciplinary Scientific and Technical Council for Standard Acceptance  "Limestone - Methods of Chemical Analysis."  Considering the proposal of the Director of the Department of Science and Technology and the Director of the Institute of Building Materials.

Issued herewith is 01 Construction Standard of Vietnam TCXD VN 312: 2004 "Limestone - Methods of Chemical Analysis."

 

DECISION:

Article 1: This Decision shall take effect fifteen days from the date of publication in the Official Gazette.  The following officials are responsible for implementing this Decision: the Head of the Ministry's Office, the Director of the Department of Science and Technology, the Director of the Institute of Building Materials, and the Heads of related units.

Article 2: Ministry of Construction

Article 3: Institute of Building Materials

 

Draft standard report

Limestone

- Methods of Chemical Analysis

Hanoi - 2003  TCXDVN ……2003

 

 

 

Code:

 

Draft standard report

Limestone

- Methods of Chemical Analysis

Hanoi - 2003  TCXDVN ……2003

TCXDVN

Construction Standard of Vietnam

CXDVN …: 2003                                           Limestone - Methods of Chemical Analysis

 

TCXDVN…:2003 compiled by the Institute of Building Materials under the Ministry of Construction, proposed by the Department of Science and Technology under the Ministry of Construction, and issued by the Ministry of Construction.

Hanoi - 2003  TCXDVN ……2003

Referenced standards

 

 

Code:

Foreword

Chemicals, reagents

Table of Contents            Page

Scope of Application           3         

Equipment, tools      3

General Provisions  3

Sampling and sample preparation      4

Determination of loss on ignition (LOI)           7

Determination of insoluble residue (IR)          8

Testing method          8

Determination of silicon dioxide (SiO         8

Determination of iron oxide (Fe        11

Determination of aluminum oxide (Al₂)   12

7.5.1 Determination of aluminum oxide (Al₂O₃)     14

) by colorimetric method₂O₃)  15

7.5.2 Determination of aluminum oxide (Al₂O₃) by complexometric titration            15

Determination of calcium oxide (CaO)₂O₃Determination of magnesium oxide (MgO)     16

Determination of titanium dioxide    17

Determination of sulfur trioxide (SO  18

Determination of chloride (Cl 19

Determination of potassium oxide (K₃)       20

) and sodium oxide (Na^-)            21

O)₂Reporting test results₂Limestone - Methods of Chemical Analysis           22

This standard specifies methods of chemical analysis for determining major components in limestone.      22

 

CXDVN …: 2003                               Limestone - Methods of Chemical Analysis

This standard may be applied to materials with similar composition to limestone (quicklime, hydrated lime, and dolomite).

Referenced standards

b) In cases where funds from organizations and individuals within and outside Vietnam are used for victim support work and victim support benefits, such activities shall be carried out in accordance with the regulations of the Ministry of Finance and the donor; in cases where there is no agreement between the donor or their authorized representative and the Ministry of Finance regarding the expenditure level, the expenditure level prescribed in this Circular shall apply.

2. Referenced standards

TCVN 4851-1989 (ISO 3696 : 1987) Laboratory water - Specifications and test methods.

TCVN 141: 1998 Cement - Methods of chemical analysis

3. General provisions:

3.1. Chemicals used in analysis must have purity not less than analytical grade (AG).

3.2. Water used in the analysis process according to TCVN 4851-89 (ISO 3696 : 1987) or water of equivalent purity (hereinafter referred to as "water").

3.3. Diluted chemicals with volume ratios are enclosed in parentheses. For example, HCl (1+2) is a solution consisting of 1 volume of concentrated HCl with 2 volumes of water.

3.4. Specific gravity (d) of concentrated reagents is calculated in g/cm

3.5. Calibration curves for colorimetric methods, spectroscopy, etc., must be checked again after two months. If there are discrepancies, the calibration curve must be re-established according to the procedures specified in the standard.

3.6. Each analytical index is performed simultaneously on two weighed samples and one blank experiment (including the quantities of reagents as specified in the standard but without the test sample) to calibrate the results.³

3.7. Reproducibility of the test:

The absolute difference between the results of two independent single tests obtained using the same method, on identical test samples, in the same laboratory, by the same operator, using the same equipment, within a short period of time, does not exceed ... in no more than 5% of cases.

3.8. The final result is the average value of two simultaneous analyses expressed as a percentage (%).

3.9. Determination of constant weight

Constant weight is determined by: heating the sample to a specified temperature and maintaining it at that temperature for 15 minutes, cooling the sample in a desiccator to room temperature and weighing. The process is repeated until the difference between two consecutive weighings does not exceed 0.0005g.

4. Chemicals, reagents

4.1 Sodium carbonate (Na

) anhydrous.

4.2 Potassium carbonate (K₂Add distilled water to make up to 1 liter of solution.₃4.3 Ammonium chloride (NH

Cl) crystals.₂Add distilled water to make up to 1 liter of solution.₃4.3 Ammonium chloride (NH

4.4 Hydrochloric acid (HCl) concentrated, d = 1.19; solution (1+1); solution (5+95); solution (1+9).₄4.5 Hydrofluoric acid (HF) concentrated, d = 1.12 (38%

4.6 Sulfuric acid (H

) concentrated, d = 1.84. ¸ 40 %).

4.7 Nitric acid (HNO₂SO₄), 10% solution.

4.8 Acetic acid (CH₃COOH) concentrated, d = 1.05

4.9 Ammonia hydroxide (NH₃OH) concentrated, d = 0.88 (25%). ¸ 1,06.

4.10 Sodium hydroxide (NaOH), 10% solution; 30% solution. Stored in polyethylene bottles.₄4.11 Potassium hydroxide (KOH), 25% solution. Stored in polyethylene bottles.

4.12 Potassium cyanide (KCN), 5% solution. Stored in polyethylene bottles.

4.13 Barium chloride (BaCl

4.14 Sulfosalicylic acid, 10% solution.

4.15 Silver nitrate (AgNO₂COOH) concentrated, d = 1.05

), 0.5% solution. Stored in amber glass bottles.

4.16 Diantipyrylmethane, 2% solution.₃Mix 25ml of concentrated sulfuric acid in 300ml of water, add 20g of diantipyrylmethane indicator, stir until completely dissolved, dilute to 1 liter. Store in amber glass bottle.

4.17 Fluorexon indicator 1%.

Grind 0.1g of fluorexon indicator with 10g of potassium chloride in a glass mortar, store in an amber glass bottle.

4.18 Eriochrome Black T indicator 0.1% solution.

Dissolve 0.1g of Eriochrome Black T in 100ml of 90% ethanol, add 3g of hydroxylamine hydrochloride, stir thoroughly. Store in dark amber glass bottle.

4.19 Ammonium iron(III) sulfate indicator, saturated solution.

4.20 Thiourea, 5% solution.

Dissolve the reagent in water.₄4.21 Xylenol orange indicator, 0.1% solution.₄)₂ Dissolve 0.1g of xylenol orange indicator in 100ml of water.

4.22 Phenolphthalein indicator, 0.1% solution.  Dissolve 0.1g of phenolphthalein in 100ml of 90% ethanol.

4.23 Buffer solution pH = 4.2

Mix 60ml of acetic acid with 300

400ml of water, add 100ml of 10% NaOH, add water to make 1 liter, stir thoroughly.

4.24 Buffer solution pH = 5.5

Dissolve 100ml of concentrated ammonia hydroxide in 300 to 400ml of water, add 100ml of acetic acid, add water to make 1 liter, stir thoroughly.

4.25 Buffer solution pH = 10.5 ¸ Dissolve 54g of ammonium chloride in 500ml of water, add 350ml of concentrated ammonia hydroxide, add water to make 1 liter, stir thoroughly.  Add water to make up to 1 liter, stir thoroughly.

4.24 Buffer solution pH = 5.5

Dissolve 100 ml of concentrated ammonium hydroxide in 300 to 400 ml of water, add 100 ml of acetic acid, add water to make up to 1 liter, stir thoroughly.

4.25 Buffer solution pH = 10.5

Dissolve 54 g of ammonium chloride in 500 ml of water, add 350 ml of concentrated ammonium hydroxide, add water to make up to 1 liter, stir thoroughly.

4.26 Standard EDTA Solution  0.01 M

Prepared from the standard tube (fixanal) EDTA 0.01 M

4.27 Standard Silver Nitrate (AgNO3) Solution 0.1 N₃) 0.1 N

Prepared from the standard tube (fixanal) AgNO3 0.1 N.₃ Store in a dark glass bottle.

4.28 Standard Ammonium Thiocyanate (NH4SCN) Solution 0.1 N₄SCN) 0.1 N

Prepared from the standard tube (fixanal) ammonium thiocyanate 0.1 N.

4.29 Standard Zinc Acetate Solution 0.01 M  acetate 0.01 M

Dissolve 2.2¸2.3 grams of Zn(CH3COO)2.2H2O in 200 ml of water, add 2 ml of concentrated acetic acid, heat until dissolved, then dilute to 1 liter.₃(CH3COO)₂.2H₂O into 200 ml of water, add 2 ml of concentrated acetic acid, heat until dissolved, dilute to 1 liter.

Determine the concentration ratio (K) between the 0.01 M EDTA solution and the 0.01 M zinc acetate solution

Take 20 ml of the 0.01 M EDTA solution (4.30) into a 250 ml volumetric flask, add 100 ml of water and 20 ml of buffer solution with pH = 5.5, add 2 to 3 drops of 0.1% xylenol orange indicator. Heat to a temperature of 70 to 80⁰C, titrate the solution while hot with the zinc acetate solution until the solution in the flask changes color from yellow to pink, record the volume of zinc acetate solution consumed (VZn).₃(CH3COO)₂ until the solution in the cup changes from yellow to pink, record the volume of the zinc solution (Zn(CH₃(CH3COO)₂ consumed (VZn).

Determine the concentration ratio (K) between the two solutions using the following formula:

                                                            VE

                                    K =         ------------

                                                           VZn

Where:

VE: Is the volume of EDTA solution taken for titration, measured in milliliters

VZn: Is the volume of zinc acetate solution consumed during titration, measured in milliliters₃(CH3COO)₂ 4.30 Aluminumon Test Solution 0.2%

Dissolve 0.2 grams  %

of aluminumon test reagent in buffer solution with pH = 4.2 (section 4.27), leave overnight before use (solution stored in brown bottle).  This solution can be used for up to one week

This solution can be used for a maximum of one week.

4.31 1% Thioctic Acid Solution, prepared daily (solution stored in brown bottle)

4.32 Standard iron oxide (Fe₂O₃ 4.32 Standard Iron Oxide Solution (Fe2O3 = 0.25 mg/ml)

Weigh approximately 0.25 g of iron oxide Fe2O3 (TKPT) on an analytical balance accurate to 0.0001 g that has been dried at 110₂O₃ C into a 100 ml glass volumetric flask, add 50 ml of hydrochloric acid (1+1) solution and gently boil until completely dissolved. Allow to cool, transfer to a 1000 ml volumetric flask, add water to the mark, shake well.⁰* Working standard solution (Fe2O3 = 0.05 mg/ml)

Take 50 ml of the original standard solution into a 250 ml volumetric flask, add water₂O₃ to the mark, shake well.

4.33 Standard Titanium Dioxide (TiO2) Solution (TiO2 = 0.1 mg/ml)  Weigh approximately 0.3005 g of potassium hexafluorotitanate K2TiF6 into a platinum dish, add 10

15 ml of sulfuric acid (1+1) solution, evaporate on an electric stove until dry, add another 5 ml of acid solution, evaporate until completely dry and stop the white smoke. Transfer to a 100 ml glass beaker using 5% HCl solution, add 5 ml of sulfuric acid (1+1) solution and boil. Remove to cool, transfer the solution to a 1000 ml volumetric flask, use 5% sulfuric acid solution to fill to the mark, shake well.₂ * Working standard solution (TiO2 = 0.04 mg/ml)

Take 100 ml of the original standard solution into a 250 ml volumetric flask, use 5% sulfuric acid solution to fill to the mark, shake well.₂4.34 Standard Aluminum Oxide (Al2O3) Solution (Al2O3 = 1 mg/ml)₆ C into a 100 ml glass volumetric flask, add 50 ml of hydrochloric acid (1+1) solution and gently boil until completely dissolved. Allow to cool, transfer to a 1000 ml volumetric flask, add water to the mark, shake well.⁰Weigh approximately 1 g of aluminum oxide Al2O3 (TKPT) ¸on an analytical balance accurate to 0.0001 g that has been dried at 110₂SO₄  C into a 250 ml volumetric flask, add 50 ml of hydrochloric acid, cover with a watch glass and boil the solution until completely dissolved. Allow to cool, transfer to a 1000 ml volumetric flask, add water to the mark, shake well.

* Working standard solution (Al2O3)₂ Take 50 ml of the original standard solution into a 500 ml volumetric flask, use 5+95 hydrochloric acid solution to fill to the mark, shake well.

5. Equipment and Tools.

5.1 Analytical Balance with accuracy of 0.0010 g₂O₃ 5.2 Oven capable of reaching 300

C, equipped with temperature control and regulation devices.₂O₃ 5.3 Furnace capable of reaching 1000 5.4 Photometer or UV-VIS spectrophotometer with wavelength range from 380 nm to 850 nm.⁰5.5 Flame photometer (FP) or atomic absorption spectrometer (AAS) equipped to measure potassium and sodium.

5.6 Electric or sand bath controlled temperature.₂O₃ * Working standard solution (TiO2 = 0.04 mg/ml)

5.7 Platinum dish with capacity of 30 ml

5.8 Standard sieves with mesh sizes of 0.5 mm, 0.25 mm, 0.125 mm, and 0.063 mm.

5.9 Mortar and pestle made of agate.

5.10 Desiccator ⁰140 mm or

200 mm ⁰C± 50 ⁰140 mm or

5.11 Volumetric flasks with capacities of 100 ml, 250 ml, 500 ml, and 1000 ml. Pipettes with capacities of 2 ml, 5 ml, 10 ml, 20 ml, 25 ml, 50 ml, and 100 ml. Burette with capacity of 25 ml. Glass beakers with capacities of 100 ml and 250 ml.

5.12 Evaporating dish

5.13 Quantitative filter paper without ash of various types:

Fast flow type, average pore diameter about 20

Medium flow type, average pore diameter about 7

Slow flow type, average pore diameter about 2

6. Sample Collection and Preparation F 6.1 Sample Collection: F The limestone sample for chemical analysis is collected according to technical sampling regulations in limestone production and usage facilities to ensure that the test sample represents the batch of raw material.

The sample delivered to the laboratory should weigh no less than 500 g, with particle size not exceeding 5 mm.

6.2 Sample Preparation:

Process the sample to pass through a 0.5 mm sieve, use a magnet to remove metal filings mixed in the sample. Mix the test sample thoroughly, use the quartering method to take about 120 g of sample, grind it finely to pass through a 0.25 mm sieve, continue to quarter and take about 50 g of sample to grind finely to pass through a 0.125 mm sieve. Continue to reduce the sample by quartering method to take about 20 g, then grind finely on an agate mortar or laboratory grinder to particle size passing through a 0.063 mm sieve. Dry the sample at 105  C until constant weight. This amount of sample is the test sample for chemical analysis. The remaining sample is stored in a sealed container (bottle or bag) as a reserve sample.

7. Testing Method Granite, gabbro, decorative stone...m shall be used.

The chemical analysis process is carried out according to the flowcharts in Figures 1 and 2 Granite, gabbro, decorative stone...m shall be used.

7.1 Determination of Loss on Ignition (LOI) Granite, gabbro, decorative stone...m shall be used.

7.1.1 Principle:

The test sample is ignited at 1000

C until constant weight. From the weight loss of the test sample, calculate the ignition loss.

7.1.2 Procedure

Weigh approximately 1 g of the test sample (section 6.2) on an analytical balance accurate to 0.0001 g, place it in a porcelain crucible that has been fired at 1000

C, cool it in a desiccator to room temperature and weigh it, then fire again at the above temperature and weigh until  constant weight. Fire the crucible containing the sample at the above temperature for about 1-1.5 hours. Remove the crucible, cool it in a desiccator to room temperature, then weigh it. Refire and weigh until a constant weight is obtained. ⁰C ± 5 ⁰When firing the crucible with the sample, start firing when the furnace temperature is still low. Then gradually increase the temperature from low to high. Because if the sample is fired immediately at a high temperature, CO2

gas will escape very strongly, and if attention is not paid to gradually increasing the temperature, it may cause loss of the analytical sample.

The chemical analysis process is carried out according to the diagrams in Figures 1 and 2.

7.1 Determination of weight loss on ignition (LOI)

7.1.1 Principle:

The test sample is heated at a temperature of 1000 ⁰C ± 50 ⁰C until constant weight. From the weight loss of the test sample, calculate the weight loss on ignition.

7.1.2 Procedure

Weigh approximately 1 g of the test sample (section 6.2) on a balance with a division of 0.0001 g, place it in a porcelain dish that has been heated at a temperature of 1000 ⁰C ± 50 ⁰C to cool in a desiccator to room temperature and weigh, reheat at the above temperature and weigh until  constant weight. Heat the dish containing the sample at the above temperature for about 1-1.5 hours. Remove the dish, cool it in a desiccator to room temperature and weigh. Reheat and weigh until a constant weight is obtained.

Note:

When heating the dish containing the sample, heating must begin when the furnace temperature is still low. Then gradually increase the temperature from low to high. Because if the sample is heated at a high temperature right from the start, CO₂ will escape very strongly, and if attention is not paid to gradually increasing the temperature, it may cause loss of the analytical sample.

The sample after calcination mainly consists of calcium oxide (CaO), which readily absorbs moisture from the air. Therefore, when weighing, it is necessary to weigh quickly to obtain accurate results.

7.1.3 Calculating the Results:

The weight loss on ignition (WLOI) is calculated as a percentage using the formula

                        g₁ - g₂

            % WLOI  =      -------------         x   100

                        Granite, gabbro, decorative stone...

Where:

g₁ : Is the weight of the dish and sample before ignition, expressed in grams

g₂ : Is the weight of the dish and sample after ignition, expressed in grams

m : Is the weight of the test sample, expressed in grams

The repeatability of the test is 0.40 %.  The precision of the test is 0.40 %.

7.2 Determining the Content of Insoluble Residue in Acid (IR)

7.2.1 Principle:

Dissolve the test sample in dilute hydrochloric acid (HCl), filter out the insoluble residue, calcine, and weigh to determine the content of insoluble residue in acid.

7.2.2 Procedure:

Weigh approximately 2 grams of the test sample (section 6.2) on a balance with a division of 0.0001 g, place it in a glass beaker with a capacity of 100 ml. Wet the sample with water. Gradually add 50 ml of HCl solution (1+9) to the beaker, wait until the bubbling stops, then gently heat the beaker on an electric stove (gentle boil for 15 minutes). Allow it to cool to about 50⁰C ¸60⁰C. Filter the solution through medium-speed ashless filter paper. Transfer the residue to a funnel, clean the beaker with ashless filter paper, rinse the residue with HCl solution (5+95) two to three times, then rinse again with hot water until all chloride ions^- (test with AgNO₃ 0,5%).

) are removed.⁰C ± 50⁰Transfer the filter paper and residue into a known weight porcelain dish, dry and burn off the filter paper slowly on an electric stove. Calcine at 1000

C for one hour and thirty minutes, remove and cool in a desiccator to room temperature and weigh. Recalcine and weigh until constant weight.

Collect the filtrate and washings in a 250 ml glass beaker for determining the total sulfur trioxide content in the test sample. (Solution 1)

                                    g₁ - g₂

            7.2.3 Calculating the Results:            =          ------------------         x          100

                                    Granite, gabbro, decorative stone...

Where:

g₁% IR

g₂ : Is the weight of the insoluble residue and dish, expressed in grams.

: Is the weight of the empty dish, expressed in grams.

m : Is the weight of the test sample, expressed in grams.

The repeatability of the test is 0.15 %.₂) :

7.3 Determining the Content of Silicon Dioxide (SiO

7.3.1 Principle:⁰C ± 50⁰Decompose the sample with hydrochloric acid (HCl), concentrate to separate water from silicic acid. Calcine the precipitate at 1000

C, treat the precipitate with hydrofluoric acid solution to separate silicon as silicon tetrafluoride. Thus, the total amount of silicon dioxide in the test sample is determined.

7.3.2 Procedure: ⁰Weigh approximately 3 grams of the test sample (section 6.2) on a balance with a division of 0.0001 g, which has been finely ground and dried, and place it in a porcelain dish. Wet the sample with water, cover the dish with a glass lid. Add concentrated HCl (1+1) until bubbling stops, then add 15 ml of concentrated HCl to the dish. Rinse the dish and lid with water. Place the dish on a boiling plate (sand bath or oil bath) at a temperature of 100 ⁰C to 110

C, concentrate until completely dry. Use a glass rod to break up any salt crystals formed. Add another 10 ml of concentrated HCl to the dish, concentrate the sample again at the above temperature to thoroughly precipitate silicon dioxide. After drying, continue concentrating the sample at the above temperature for 1 to 2 hours.⁰Cool the test sample, add 10 ml of concentrated HCl to the dish, let stand for 10 minutes, then add 80 ml to 100 ml of boiled water to the dish, stir evenly, and gently heat to dissolve the salts. Rinse the lid and sides of the dish with boiled water. Remove the dish and cool to 50⁰4. Liquid bull semen

C to 60^- C.₃ 0,5 %).

Filter the hot solution in the porcelain dish through medium-speed ashless filter paper, rinse the precipitate and sides of the dish with warm dilute HCl solution (5+95), use ashless filter paper to clean the glass rod and sides of the dish. Continue rinsing with boiled water until all chloride ions

(test with AgNO⁰C ± 50⁰) are removed.₁).

Collect the filtrate and washings in a 250 ml volumetric flask.₂SO₄ Transfer the filter paper and precipitate into a platinum dish, dry and burn off the filter paper on an electric stove. Calcine the dish at 1000

C for one hour and thirty minutes, remove and cool in a desiccator to room temperature and weigh. Recalcine at the above temperature until constant weight (g⁰C ± 50⁰).₂).

Wet the precipitate in the dish with a few drops of distilled water, add 2-3 drops of H₂Add distilled water to make up to 1 liter of solution.₃ + K₂Add distilled water to make up to 1 liter of solution.₃ (1+1) solution and 5 ml of 40% HF solution, evaporate the contents in the dish on an electric stove to dryness and stop the white smoke.⁰C ± 50⁰Place the dish in a furnace at 1000

C for 30 minutes, remove and cool in a desiccator to room temperature and weigh. Repeat the calcination process for 15 minutes, cool and weigh until constant weight (g₂O₃).₂O₃Calcine the remaining precipitate in the platinum dish with 2-3 grams of molten Na₂ (1:1) mixture at 1000

C for 20 minutes. Remove and cool, transfer the fused mass into a 250 ml glass beaker, rinse and clean the platinum dish. Gradually add concentrated HCl (1+1) to the beaker until bubbling stops, heat the solution in the beaker until dissolved. Cool and combine this solution with the solution in the 250 ml volumetric flask, make up to volume with water, shake well (solution 2).

This solution is used to determine the components Fe₂, Al

                                    g₁ - g₂

            , TiO₂ =          -------------------        x          100

                                    Granite, gabbro, decorative stone...

Where:

g₁ in the test sample.

g₂ 7.3.3 Calculating the Results:

: Is the weight of the empty dish, expressed in grams.

m : Is the weight of the test sample, expressed in grams.

The content of silicon dioxide (SiO₂O₃) is calculated as a percentage using the formula:

% SiO

: Is the weight of the platinum dish and precipitate before treatment with HF acid, expressed in grams. ¸ : Is the weight of the platinum dish and precipitate after treatment with HF acid, expressed in grams.

7.4 Determining the Content of Iron Oxide (Fe

) by Colorimetry.¸7.4.1 Principle:

In an alkaline ammonia environment, iron (III) ions form a yellow-colored complex with the reagent sulfosalicylic acid, the intensity of which is proportional to the concentration of iron in the solution. Compare the color of the solution at a wavelength of 420 nm ¸ 430 nm.

7.4.2 Procedure:

Take 25 ml of solution 2 (section 7.3.2) and place it in a 100 ml volumetric flask, add water to about 50 ml, then add 10 ml of 10% sulfosalicylic acid solution, and gradually add concentrated ammonium hydroxide drop by drop while shaking the flask until the solution turns yellow. Add an additional 2₂O₃ 3 ml of concentrated ammonium hydroxide, make up to volume with water, and shake well.¸After 15 minutes, compare the color of the solution at a wavelength of 420 nm

In an alkaline ammonia environment, iron (III) ions form a yellow-colored complex with the reagent sulfosalicylic acid, the intensity of which is proportional to the concentration of iron in the solution. Compare the color of the solution at a wavelength of 420 nm ¸ 430 nm, using a blank solution as the reference. Based on the standard curve, find the amount of iron oxide in 25 ml of solution 2.  is the white sample solution. Based on the iron oxide content in each bottle and the corresponding optical density values, construct a standard graph.

7.4.3 Calculate the results:

                                    Granite, gabbro, decorative stone...₁

            % Fe₂O₃          =          --------------------      x          100

                                    Granite, gabbro, decorative stone...

Where:

Granite, gabbro, decorative stone...₁ : The amount of iron oxide found from the standard graph, expressed in grams.

m : The amount of sample taken to determine the iron oxide, expressed in grams.

7.5. Determining the aluminum oxide content (Al₂O₃)

7.5.2 Determination of aluminum oxide (Al₂O₃) by complexometric titration

(For samples with aluminum oxide content less than 0.10%)

7.5.1.1 Principle:

In a solution with pH = 4.2, in the presence of thioglycolic acid, aluminum forms a red-colored complex with the aluminon reagent, the intensity of which is proportional to the concentration of aluminum in the solution. Compare the color of the solution at a wavelength of approximately 530 nm ¸ 535 nm.

7.5.1.2 Procedure:

Take 25 ml of solution 2 (section 7.3.2) and place it in a 100 ml volumetric flask. Adjust the solution to neutrality using NH₄OH solution. Add  2 ml of 1% thioglycolic acid solution and 20 ml of buffer solution with pH = 4.2 to the flask, then add water up to about 80 ml. After that, add 1 ml of 0.2% aluminon reagent to the flask, top up with water to the mark, shake well.

After 2 hours, compare the color of the solution at a wavelength of 530 nm ¸ 535 nm, using the white sample solution as the reference. Based on the standard graph, determine the amount of aluminum oxide in 25 ml of solution 2.

* Constructing the standard graph:

Take 6 100 ml volumetric flasks, sequentially add different volumes of working aluminum oxide standard solution (Al₂O₃ = 0.1 mg/ml) (section 4.34) in the following order: 0 ml; 1 ml; 3 ml; 5 ml; 7 ml; 9 ml. Sequentially add 2 ml of 1% thioglycolic acid solution and 20 ml of buffer solution with pH = 4.2 to each flask, then add distilled water up to 80 ml, add 1 ml of 0.2% aluminon reagent to each flask, top up with distilled water to the mark, shake well. After 2 hours, compare the color of the solution at a wavelength of 530 nm ¸ 535 nm, using the white sample solution as the reference. Based on the aluminum oxide content in each flask and the corresponding optical density values, construct the standard graph.

7.5.1.3 Calculate the results:

The aluminum oxide content (Al₂O₃) is calculated as a percentage according to the formula:

                                    Granite, gabbro, decorative stone...₁

            % Al₂O₃           =          ----------------            x          100

                                    Granite, gabbro, decorative stone...

Where:

Granite, gabbro, decorative stone...₁ : The amount of aluminum oxide found from the standard graph, expressed in grams.

m : The amount of sample taken to determine the aluminum oxide, expressed in grams.

Determination of calcium oxide (CaO)₂O₃Determination of magnesium oxide (MgO)

(For samples with aluminum oxide content of 0.10  % or more)

7.5.2.1 Principle:

Remove calcium and magnesium from the solution by precipitating aluminum with 25% ammonium hydroxide (NH₄OH) solution, then dissolve the precipitate again with HCl (1+1) acid. Separate aluminum from interfering elements such as iron, titanium... using strong alkali. Form a complex between aluminum and excess EDTA at pH = 5.5. Titrate the excess EDTA with zinc acetate solution according to the xylene orange indicator. Use sodium fluoride to release EDTA from the complex, titrate the released EDTA with a standard zinc acetate solution 0.01 M, thereby calculating the aluminum content.

7.5.2.2 Procedure:

Take 100 ml of solution 2 (section 7.3.2) and place it in a 250 ml glass beaker, add 1 ¸ 2 g of NH₄Cl to the beaker, stir thoroughly, heat the solution, add 1¸2 drops of methyl red indicator to the beaker. Slowly add NH₄OH 25% solution to the beaker while stirring until the solution in the beaker turns yellow, then add an additional drop of NH₄OH. Gently boil the solution in the beaker, filter the solution while hot through a fast-flowing filter paper, wash the precipitate and the glass beaker 2¸3 times with hot distilled water.

Dissolve the precipitate on the filter paper back into the beaker with HCl (1+1) acid, use preheated HCl (5+95) solution to rinse the funnel clean, continue rinsing with hot distilled water until chloride ions are less than 0.5%. Add 20 ml of 30% NaOH solution to the glass beaker, stir thoroughly, boil the solution for 1^- C.₃ 2 minutes, cool it down, then transfer the solution in the beaker to a 250 ml volumetric flask, top up with distilled water to the mark, shake well. Filter the solution through a fast-flowing filter paper (dry), funnel (dry) into a 250 ml conical flask (dry). The filtered solution is used to determine aluminum (solution A).¸Take 100 ml of solution A and place it in a 250 ml glass beaker, add 20 ml of 0.01 M EDTA solution to the beaker, add 1

2 drops of 0.1% phenolphthalein indicator to the beaker, adjust the solution to neutrality (loss of pink color) with HCl (1+1) and 10% NaOH solutions, then add 15 ml of pH = 5.5 buffer solution to the beaker.¸ Heat the solution in the beaker to about 80

C, add a few drops of 0.1% xylene orange indicator to the beaker and titrate with 0.01 M zinc acetate solution until the solution changes from yellow to pink. ⁰Add 10 ml of 3% NaF solution to the beaker and boil for 3 minutes, the solution now has a yellow color, cool the solution to 70

C and titrate the released EDTA with 0.01 M zinc acetate solution until the solution changes from yellow to pink, record the volume of 0.01 M zinc acetate solution consumed.¸80 ⁰7.5.2.3 Calculate the results:

0,0005098 x VZn

The aluminum oxide content (Al₂O₃, Al

                                                             0,0005098: The amount of aluminum oxide corresponding to 1 ml of 0.01 M zinc acetate solution.  x K

            % Al₂O₃           =          ----------------------------------------            x          100                                                                         Granite, gabbro, decorative stone...

Where:

VZn: The volume of 0.01 M zinc acetate solution consumed during the titration of the released EDTA, expressed in milliliters.

K: The concentration factor between the 0.01 M zinc acetate solution and the 0.01 M EDTA standard solution (section 4.29).

m: The amount of sample taken to determine the aluminum oxide content, expressed in grams.

7.6 Determining the calcium oxide content (CaO)

7.6.1 Principle:

Decompose the sample with hydrochloric acid (HCl). Titrate the calcium content with 0.01 M EDTA standard solution at pH > 12 with the fluorexon indicator, at the equivalence point the solution loses its fluorescent green color and turns pink.

7.6.2 Procedure:

Weigh approximately 0.2 g of the test sample (section 6.2) on a balance accurate to 0.0001 g and place it in a 100 ml glass beaker. Wet the sample with water. Gradually add 10 ml of HCl (1+1) to the beaker, heat until dissolved. Remove, cool, then transfer the solution to a 250 ml volumetric flask. Top up with distilled water to the mark, shake well (solution 3).

Take 25 ml of solution 3 and place it in a 250 ml beaker, top up with distilled water to about 100 ml. Add 20 ml of 25% KOH, 2 ml of 5% KCN, and a small amount of fluorexon indicator to the beaker.

Place the beaker on a black background, titrate the solution in the beaker with 0.01 M EDTA solution until the solution changes from fluorescent green to pink. Record the volume of 0.01 M EDTA solution consumed.

Simultaneously perform a blank experiment to correct for the calcium content in the solution and the reagents. Record the volume of 0.01 M EDTA solution consumed.

7.6.3 Calculate the results:

The calcium oxide content is calculated as a percentage according to the formula:

0,00056 (V

                                    % CaO₁ - V (VND/year): is the total investment capital allocated annually for the usable area of social housing for rent, ensuring the preservation of capital, calculated according to the following formula:₀)

            : The volume of 0.01 M EDTA solution consumed during the titration of the sample, expressed in milliliters.            =          --------------------------------------   x          100

                                    Granite, gabbro, decorative stone...

Where:

V₁: Is the volume of 0.01 M EDTA consumed during titration of the test sample, expressed in milliliters.

V₀: Is the volume of 0.01 M EDTA consumed when titrating the blank sample, expressed in milliliters.

m : The amount of sample taken to determine calcium oxide content, expressed in grams.

0,00056 : Is the mass of calcium oxide corresponding to 1 mL of 0.01 M EDTA solution, expressed in grams.

The repeatability of the test is 0.30%.

 

7.7 Determination of Magnesium Oxide (MgO) Content

7.7.1 Principle:

Titrate the total amount of calcium and magnesium in the sample with standard EDTA solution according to the black eriochrome T indicator at pH = 10.5.

Determine the magnesium oxide content based on the difference in the volume of EDTA consumed when titrating the total amount of calcium and magnesium at pH = 10.5 and when titrating calcium alone at pH > 12.

7.7.2 Procedure:

Take 25 mL of solution 3 (section 7.6.2) into a 250 mL volumetric flask, add water up to approximately 100 mL. Add 20 mL of buffer solution pH = 10.5; 2 mL of 5% KCN and 2 ¸ 3 drops of 0.1% eriochrome T black indicator. Titrate the total amount of calcium and magnesium with 0.01 M EDTA solution until the solution changes from red-purple to blue-green. Record the volume of EDTA consumed.

Conduct a parallel blank experiment to calibrate the total amount of calcium and magnesium present in the reagents. Record the volume of EDTA consumed.

7.7.3 Calculation of Results:

The magnesium oxide content, expressed as a percentage, is calculated using the formula:

 

                                         0,000403 [(V₂-V₀₂) - (V₁-V₀₁)]

            % MgO            =          --------------------------------------------      x          100

                                    Granite, gabbro, decorative stone...

Where:

V₂: Is the volume of 0.01 M standard EDTA solution consumed when titrating the total amount of calcium and magnesium in the sample solution, expressed in milliliters.

V₀₂: Is the volume of 0.01 M standard EDTA solution consumed when titrating the total amount of calcium and magnesium in the blank sample, expressed in milliliters.

V₁: Is the volume of 0.01 M standard EDTA solution consumed when titrating the individual amount of calcium in the sample solution, expressed in milliliters.

V₀₁: Is the volume of 0.01 M standard EDTA solution consumed when titrating the individual amount of calcium in the blank sample, expressed in milliliters.

m: Is the amount of sample taken to determine magnesium oxide, expressed in grams.

0,000403: Is the mass of magnesium oxide corresponding to 1 mL of 0.01 M EDTA solution, expressed in grams.

The repeatability of the test is 0.35%, (applicable for dolomite raw materials).

7.8. Determination of Titanium Dioxide (TiO₂) Content by Colorimetry Method.

7.8.1 Principle:

Dianisidine creates a yellow complex with titanium (IV) ions in a strong acid medium, the intensity of which is proportional to the concentration of titanium in the solution. Compare the color of the solution at a wavelength of about 400 nm ¸ 420 nm.

7.8.2 Procedure:

Take 25 mL of solution 2 (section 7.3.2) into a 100 mL volumetric flask. Add 15 mL of concentrated HCl (1+1) solution, 5 mL of thiourea 5% solution, shake well, let the solution stand until it loses its yellow color due to iron (the solution turns colorless). Add 15 mL of 2% dianisidine solution, top up with distilled water to the mark, shake well.

After 1 hour, compare the color of the solution at a wavelength of 400 nm ¸ 420 nm, the reference solution being the blank sample solution. Based on the measured optical density value, find the amount of titanium dioxide in 25 mL of solution 2 from the calibration curve.

* Constructing the standard graph:

Take 6 100 mL volumetric flasks, sequentially add different volumes of working standard titanium dioxide solution (TiO₂ = 0.04 mg/mL) (section 4.33) in the following order: 0 mL; 2 mL;   4 mL; 6 mL; 8 mL; 12 mL. Add 15 mL of concentrated HCl (1+1) solution, 5 mL of thiourea   5%... continue with the above procedures.

After 1 hour, compare the color of the solution at a wavelength of 400 nm ¸ 420 nm. From the amount of titanium dioxide in each flask and the corresponding optical density values, construct the calibration curve.

7.8.3 Calculation of Results:

                                                           Granite, gabbro, decorative stone...₁

            % TiO₂ =          ---------------  x          100

                                                                        Granite, gabbro, decorative stone...

Where:

Granite, gabbro, decorative stone...₁: Is the amount of titanium dioxide obtained from the calibration curve, expressed in grams.

m: Is the amount of sample taken to determine titanium dioxide, expressed in grams.

7.9. Determination of Sulfur Trioxide (SO₃)

7.9.1 Principle:

Determine the sulfur trioxide (SO₃ ) content from solution 1 (section 7.2). Then precipitate sulfate as barium sulfate in an acidic environment. Burn the precipitate at 850 ⁰C, from which the sulfur trioxide content is calculated.₃ (1:1) mixture at 1000

7.9.2 Procedure

Take solution 1 (section 7.2) for determining insoluble residue in acid into a 250 mL glass beaker. Gently boil this solution while heating 10% barium chloride solution.

Gradually add 10 mL of 10% barium chloride solution to the beaker, stir thoroughly, continue boiling gently for 5 minutes. Let the precipitate settle in a warm place (40 ⁰C ¸ 50 ⁰C) for 4 to 8 hours.

Filter the precipitate through slow-flowing ash-free filter paper, wash the precipitate and filter paper five times with hot diluted hydrochloric acid (5+95). Continue washing with boiled distilled water until all chloride ions are removed.^- C.₃ 0,5 %).

Transfer the filter paper and precipitate into a previously fired porcelain dish, weigh until constant weight. Dry and burn off the filter paper on an electric stove. Burn at 800⁰C to 850 ⁰C for 60 minutes.

Remove the dish to cool in a desiccator to room temperature, weigh, then re-fire at the above temperature until constant weight.

7.9.3 Calculation of Results:

The anhydrous sulfuric acid (SO₃, Al

                                    0,343 x (g₁ - g₂)

            % SO₃             =          -----------------------  x          100

                                    Granite, gabbro, decorative stone...

Where:

g₁: Is the weight of the dish containing the precipitate, expressed in grams.

g₂: Is the weight of the insoluble residue and dish, expressed in grams.

m: Is the weight of the sample taken to determine SO₃, expressed in grams.

0,343: Is the conversion factor from BaSO₄ to SO₃.

7.10. Determination of Chloride (Cl^-)

7.10.1 Principle:

Precipitate chloride with silver nitrate, titrate the excess silver nitrate with ammonium thiocyanate.

7.10.2 Procedure

Weigh approximately 2 grams of the sample (section 6.2) on a balance accurate to 0.0001 grams, place it in a 250 mL glass beaker, moisten the sample with distilled water, add 50 mL of 10% nitric acid (HNO₃) solution. Boil to dissolve the sample, cool, dilute the solution to about 150 mL with water. Accurately add 5 mL of 0.1 N silver nitrate (AgNO₃) solution and 1¸2 mL of ferric ammonium sulfate NH₄Fe(SO₄)₂solution, titrate the excess silver nitrate (AgNO₃) with standard 0.1 N ammonium thiocyanate (NH₄SCN) solution until the solution turns brownish-red.

Conduct a parallel blank experiment to correct for the chloride ions in the reagents, record the volume consumed as V₀

7.10.3 Calculation of Results:

                        (V₀ - V) x 0,003546

            % Cl^-  =           ---------------------------------           x          100

                        Granite, gabbro, decorative stone...

Where:

V₀: Is the volume of 0.1 N standard NH₄SCN solution consumed when titrating the blank sample, expressed in milliliters.

V: Is the volume of 0.1 N standard NH₄SCN solution consumed when titrating the test sample, expressed in milliliters.

m: Is the weight of the weighed sample, expressed in grams.

0,003546 is the mass of chlorine (Cl^-) corresponding to 1 mL of 0.1 N NH₄SCN solution, expressed in grams.

7.11. Determination of Potassium Oxide (K₂Reporting test results₂Limestone - Methods of Chemical Analysis

(Referenced from section 7.16 of TCVN 141: 1998 standard)

8. Reporting Test Results:

The test report should include the following information:

- Necessary information to fully identify the sample;

- Steps for conducting the test that differ from the provisions of this standard (specify the referenced documents);

- Test results (including the determination results of potassium oxide and sodium oxide content as per Clause 7.16 TCVN 141:1998);

- Situations affecting the test results;

- Date of the test conducted.