Iron is made from ore (usually hematite, Fe 2 O 3 ) and carbon monoxide (CO) in a huge reactor called a blast furnace.Iron is made from ore (usually hematite, Fe 2 O 3 ) and carbon monoxide (CO) in a huge reactor called a blast furnace. A charge of iron ore, coke (coal cake, C), and limestone (CaCO 3 ) are added at the top of the furnace, and a blast of hot air is sent up from the bottom. The coke burns at 1,500° C to 2,000° C and makes CO.A charge of iron ore, coke (coal cake, C), and limestone (CaCO 3 ) are added at the top of the furnace, and a blast of hot air is sent up from the bottom. The coke burns at 1,500° C to 2,000° C and makes CO. 2C (s) + O 2(g) 2CO (g) As the charge falls, the CO (g) raises and causes the Fe 2 O 3 to be reduced to Fe.As the charge falls, the CO (g) raises and causes the Fe 2 O 3 to be reduced to Fe. Fe 2 O 3(s) + 3CO (g) 2Fe (l) + 3CO 2(g) The CaCO 3 removes the impurities as slag.The CaCO 3 removes the impurities as slag. CaCO 3(s) CaO (s) + CO 2(g) CaO (s) + SiO 2(s) CaSiO 3(l) Lime + Sand Slag CH 104: DETERMINATION OF MANGANESE IN STEEL THE MANUFACTURE OF IRON

The iron made by a blast furnace is called pig or cast iron.The iron made by a blast furnace is called pig or cast iron. It is brittle and has approximately 4% C and smaller amounts of other impurities such as Mn, P, S, and Si.It is brittle and has approximately 4% C and smaller amounts of other impurities such as Mn, P, S, and Si. THE MANUFACTURE OF IRON

A modern blast furnace produces nearly 10,000,000 kg (11,000 tons) of pig iron per day.A modern blast furnace produces nearly 10,000,000 kg (11,000 tons) of pig iron per day. This pig iron is used to manufacture steel.This pig iron is used to manufacture steel. THE MANUFACTURE OF IRON

Steel is refined Fe that has less than 1.7% C. This process has 3 requirements.Steel is refined Fe that has less than 1.7% C. This process has 3 requirements. First, the approximately 4% C in pig iron is lowered to less than 1.7% C.First, the approximately 4% C in pig iron is lowered to less than 1.7% C. Second, the Mn, P, S, and Si impurities from pig iron are removed as slag.Second, the Mn, P, S, and Si impurities from pig iron are removed as slag. Third, alloying elements, such as Cr, Mn, Mo, Ni, V, and W, are added to give the steel its desired properties.Third, alloying elements, such as Cr, Mn, Mo, Ni, V, and W, are added to give the steel its desired properties. Approximately 800 million tons of steel is produced each year. That is, over 250 pounds of steel is made for each person on Earth each year.Approximately 800 million tons of steel is produced each year. That is, over 250 pounds of steel is made for each person on Earth each year. THE MANUFACTURE OF STEEL

Molten pig iron from the blast furnace is typically poured into a basic oxygen furnace and made into steel.Molten pig iron from the blast furnace is typically poured into a basic oxygen furnace and made into steel. Some of the C in pig iron is oxidized with O 2(g) and removed as CO (g) and CO 2(g).Some of the C in pig iron is oxidized with O 2(g) and removed as CO (g) and CO 2(g). The inorganic impurities in pig iron are oxidized with O 2(g), reacted with basic oxides, and removed as slag.The inorganic impurities in pig iron are oxidized with O 2(g), reacted with basic oxides, and removed as slag. P 4(l) + 5O 2(g) P 4 O 10(l) 6CaO (s) + P 4 O 10(l) 2Ca 3 (PO 4 ) 2(l) Basic Oxide + Acidic Oxide Slag THE MANUFACTURE OF STEEL

Finally, alloying elements, such as Cr, Mn, Mo, Ni, V, and W, are added to give the steel its desired properties.Finally, alloying elements, such as Cr, Mn, Mo, Ni, V, and W, are added to give the steel its desired properties. For example, Cr, Mo, and Ni give corrosion resistance to stainless steels.For example, Cr, Mo, and Ni give corrosion resistance to stainless steels. Manganese (Mn) makes steel easier to deform at high temperatures. It is added to help the rolling and forging steps of steel production.Manganese (Mn) makes steel easier to deform at high temperatures. It is added to help the rolling and forging steps of steel production. In todays experiment you will measure the Mn content of steel.In todays experiment you will measure the Mn content of steel. You will be graded on the accuracy of your result.You will be graded on the accuracy of your result. THE MANUFACTURE OF STEEL

Tare a 250 mL Erlenmeyer flask.Tare a 250 mL Erlenmeyer flask. Accurately weigh 0.3 g of steel to 3 significant digits into this flask. For example, your sample might weigh g. Record this mass in your data sheet.Accurately weigh 0.3 g of steel to 3 significant digits into this flask. For example, your sample might weigh g. Record this mass in your data sheet. Perform this step in a FUME HOOD. CAREFULLY add 50 mL of 6 M (dilute) nitric acid (HNO 3 ). If necessary, carefully heat the reaction mixture on a hot plate until all the steel is dissolved. The purpose of this step is to dissolve the manganese.Perform this step in a FUME HOOD. CAREFULLY add 50 mL of 6 M (dilute) nitric acid (HNO 3 ). If necessary, carefully heat the reaction mixture on a hot plate until all the steel is dissolved. The purpose of this step is to dissolve the manganese. Mn (s) + 4HNO 3(aq) Mn 2+ (aq) + 2NO 3– (aq) + 2NO 2(g) + 2H 2 O (l) SAMPLE PREPARATION

Perform this step in a FUME HOOD. CAREFULLY add 1 g of ammonium peroxydisulfate ((NH 4 ) 2 S 2 O 8 ) and boil gently for 10 minutes. The purpose of this step is to remove any color from carbon-containing compounds.Perform this step in a FUME HOOD. CAREFULLY add 1 g of ammonium peroxydisulfate ((NH 4 ) 2 S 2 O 8 ) and boil gently for 10 minutes. The purpose of this step is to remove any color from carbon-containing compounds. 2S 2 O 8 2– (aq) + C (aq) + 2H 2 O (l) CO 2(g) + 4SO 4 2– (aq) + 4H + (aq) Perform this step in a FUME HOOD. CAREFULLY add 0.1 g of sodium hydrogen sulfite (NaHSO 3 ) and heat for another 5 minutes. The purpose of this step is to remove any color from permanganate ion (MnO 4 – ).Perform this step in a FUME HOOD. CAREFULLY add 0.1 g of sodium hydrogen sulfite (NaHSO 3 ) and heat for another 5 minutes. The purpose of this step is to remove any color from permanganate ion (MnO 4 – ). 5HSO 3 – (aq) + 2MnO 4 – (aq) + H + (aq) 2Mn 2+ (aq) + 5SO 4 2– (aq) + 3H 2 O (l) Perform this step in at your bench. You are done using the fume hood. Cool and dilute the solution to exactly 100 mL in a volumetric flask. Shake well to mix.Perform this step in at your bench. You are done using the fume hood. Cool and dilute the solution to exactly 100 mL in a volumetric flask. Shake well to mix. SAMPLE PREPARATION

Pipet three 25 mL aliquots of the sample into small beakers. Treat these aliquots by adding the following reagents:Pipet three 25 mL aliquots of the sample into small beakers. Treat these aliquots by adding the following reagents: Boil aliquots 1 and 2 gently for 5 minutes and cool.Boil aliquots 1 and 2 gently for 5 minutes and cool. Dilute each of the 3 aliquots to 100 mL in volumetric flasks.Dilute each of the 3 aliquots to 100 mL in volumetric flasks. The nearly colorless manganese(II) ion (Mn 2+ ) is oxidized to the purple permanganate ion (MnO 4 – ).The nearly colorless manganese(II) ion (Mn 2+ ) is oxidized to the purple permanganate ion (MnO 4 – ). 5IO 4 – + 2Mn H 2 O 2MnO 4 – + 5IO 3 – + 6H + You will measure the concentrations of MnO 4 – in these 3 aliquots with a spectrophotometer at 525 nanometers (nm).You will measure the concentrations of MnO 4 – in these 3 aliquots with a spectrophotometer at 525 nanometers (nm). SAMPLE PREPARATION Aliquot Concentrated H 3 PO 4 Standard Mn KIO to 5 mL 0.00 mL 5.00 mL 0.00 mL 0.4 g 0.0 g

The standard addition method is used eliminate or reduce interference from the sample matrix. It has 3 steps.The standard addition method is used eliminate or reduce interference from the sample matrix. It has 3 steps. First, the signal from a sample is measured.First, the signal from a sample is measured. Second, the signal from a mixture of this sample and a known amount of standard is measured.Second, the signal from a mixture of this sample and a known amount of standard is measured. Third, these data are used to calculate the concentration of analyte in the sample.Third, these data are used to calculate the concentration of analyte in the sample. SAMPLE ANALYSIS BY STANDARD ADDITION

Dilute each of the 3 aliquots to 100 mL in volumetric flasks.Dilute each of the 3 aliquots to 100 mL in volumetric flasks. What is the purpose of Aliquot 1?What is the purpose of Aliquot 1? All the Mn is from the sample. All this Mn is oxidized to MnO 4 –. Aliquot 1 is used to measure the concentration of Mn in the sample.All the Mn is from the sample. All this Mn is oxidized to MnO 4 –. Aliquot 1 is used to measure the concentration of Mn in the sample. What is the purpose of Aliquot 2?What is the purpose of Aliquot 2? All the Mn is from the sample and the standard. All this Mn is oxidized to MnO 4 –. Aliquot 2 is used to measure the total concentration of Mn in the sample and in the standard.All the Mn is from the sample and the standard. All this Mn is oxidized to MnO 4 –. Aliquot 2 is used to measure the total concentration of Mn in the sample and in the standard. What is the purpose of Aliquot 3?What is the purpose of Aliquot 3? All the Mn is from the sample. None of this Mn is oxidized to MnO 4 –. Aliquot 3 is used to set the spectrophotometer to 0 absorbance (100% transmittance). This accounts for any color from the sample not from MnO 4 –. Therefore, aliquot 3 is a blank and it is used to remove interferences.All the Mn is from the sample. None of this Mn is oxidized to MnO 4 –. Aliquot 3 is used to set the spectrophotometer to 0 absorbance (100% transmittance). This accounts for any color from the sample not from MnO 4 –. Therefore, aliquot 3 is a blank and it is used to remove interferences. Aliquot Concentrated H 3 PO 4 Standard Mn KIO to 5 mL 0.00 mL 5.00 mL 0.00 mL 0.4 g 0.0 g SAMPLE ANALYSIS BY STANDARD ADDITION

Applying Beers Law to this experiment:Applying Beers Law to this experiment: A = abc A= absorbanceA= absorbance a = the absorptivity constant for MnO 4 –a = the absorptivity constant for MnO 4 – b = the path length of the sample cellb = the path length of the sample cell c = the concentration of MnO 4 – in the sample cellc = the concentration of MnO 4 – in the sample cell Since a (absorptivity) and b (path length) are constant for a given wavelength and a given sample cell, A (absorbance) is directly proportional to c (concentration):Since a (absorptivity) and b (path length) are constant for a given wavelength and a given sample cell, A (absorbance) is directly proportional to c (concentration): SAMPLE ANALYSIS BY STANDARD ADDITION

Furthermore, absorbances are additive:Furthermore, absorbances are additive: A total = A 1 + A 2 + A 3 + … The absorbance of aliquot 1 (A aliquot1 ) is caused by the Mn from the sample being oxidized to MnO 4 –. Therefore, the absorbance ofThe absorbance of aliquot 1 (A aliquot1 ) is caused by the Mn from the sample being oxidized to MnO 4 –. Therefore, the absorbance of aliquot 1 (A aliquot1 ) equals the absorbance of the sample (A sample ). A 1 = A aliquot1 = A sample The absorbance of aliquot 2 is caused by the Mn from the sample and standard being oxidized to MnO 4 –. Therefore, the absorbance ofThe absorbance of aliquot 2 is caused by the Mn from the sample and standard being oxidized to MnO 4 –. Therefore, the absorbance of aliquot 2 (A aliquot2 ) equals the absorbance of the sample (A sample ) plus the absorbance of the standard (A standard ). A 2 = A aliquot2 = A sample + A standard SAMPLE ANALYSIS BY STANDARD ADDITION

Solving for the concentration of Mn in the sample cell:Solving for the concentration of Mn in the sample cell: c standard is the concentration of Mn in the sample cell. It is NOT the concentration of Mn in the bottle of Standard Mn.c standard is the concentration of Mn in the sample cell. It is NOT the concentration of Mn in the bottle of Standard Mn. c sample is the concentration of Mn in the sample cell. It is NOT the concentration of Mn in steel.c sample is the concentration of Mn in the sample cell. It is NOT the concentration of Mn in steel. SAMPLE ANALYSIS BY STANDARD ADDITION

A g sample of steel is oxidized, dissolved, diluted to mL, and prepared as follows.A g sample of steel is oxidized, dissolved, diluted to mL, and prepared as follows. Afterwards, each of the 3 aliquots were diluted to mL. The Standard Mn solution contained mg of Mn / L. A aliquot1 equaled A aliquot2 equaled Afterwards, each of the 3 aliquots were diluted to mL. The Standard Mn solution contained mg of Mn / L. A aliquot1 equaled A aliquot2 equaled What is c standard ?What is c standard ? Again, c standard is the concentration of Mn in the sample cell. It is NOT mg of Mn / L.Again, c standard is the concentration of Mn in the sample cell. It is NOT mg of Mn / L. Aliquot Concentrated H 3 PO 4 Standard Mn KIO to 5 mL 0.00 mL 5.00 mL 0.00 mL 0.4 g 0.0 g SAMPLE ANALYSIS BY STANDARD ADDITION

A g sample of steel is oxidized, dissolved, diluted to mL, and prepared as follows.A g sample of steel is oxidized, dissolved, diluted to mL, and prepared as follows. Afterwards, each of the 3 aliquots were diluted to mL. The Standard Mn solution contained mg of Mn / L. A aliquot1 equaled A aliquot2 equaled Afterwards, each of the 3 aliquots were diluted to mL. The Standard Mn solution contained mg of Mn / L. A aliquot1 equaled A aliquot2 equaled What is c sample ?What is c sample ? Again, c sample is the concentration of Mn in the sample cell. It is NOT the concentration of Mn in steel.Again, c sample is the concentration of Mn in the sample cell. It is NOT the concentration of Mn in steel. Aliquot Concentrated H 3 PO 4 Standard Mn KIO to 5 mL 0.00 mL 5.00 mL 0.00 mL 0.4 g 0.0 g SAMPLE ANALYSIS BY STANDARD ADDITION

A g sample of steel is oxidized, dissolved, diluted to mL, and prepared as follows.A g sample of steel is oxidized, dissolved, diluted to mL, and prepared as follows. Afterwards, each of the 3 aliquots were diluted to mL. The Standard Mn solution contained mg of Mn / L. A aliquot1 equaled A aliquot2 equaled Afterwards, each of the 3 aliquots were diluted to mL. The Standard Mn solution contained mg of Mn / L. A aliquot1 equaled A aliquot2 equaled How many grams of Mn are in this steel sample?How many grams of Mn are in this steel sample? Aliquot Concentrated H 3 PO 4 Standard Mn KIO to 5 mL 0.00 mL 5.00 mL 0.00 mL 0.4 g 0.0 g SAMPLE ANALYSIS BY STANDARD ADDITION

A g sample of steel is oxidized, dissolved, diluted to mL, and prepared as follows.A g sample of steel is oxidized, dissolved, diluted to mL, and prepared as follows. Afterwards, each of the 3 aliquots were diluted to mL. The Standard Mn solution contained mg of Mn / L. A aliquot1 equaled A aliquot2 equaled Afterwards, each of the 3 aliquots were diluted to mL. The Standard Mn solution contained mg of Mn / L. A aliquot1 equaled A aliquot2 equaled What is the % Mn in this steel?What is the % Mn in this steel? Aliquot Concentrated H 3 PO 4 Standard Mn KIO to 5 mL 0.00 mL 5.00 mL 0.00 mL 0.4 g 0.0 g SAMPLE ANALYSIS BY STANDARD ADDITION

Give at least 1 safety concern for the following procedure.Give at least 1 safety concern for the following procedure. Using acids (HNO 3 and H 3 PO 4 ), oxidizing agents (HNO 3, (NH 4 ) 2 S 2 O 8, KIO 4, and KMnO 4 ), and reducing agents (Mn 2+ and NaHSO 3 ).Using acids (HNO 3 and H 3 PO 4 ), oxidizing agents (HNO 3, (NH 4 ) 2 S 2 O 8, KIO 4, and KMnO 4 ), and reducing agents (Mn 2+ and NaHSO 3 ). These are irritants. Wear your goggles at all times. Immediately clean all spills. If you do get either of these in your eye, immediately flush with water.These are irritants. Wear your goggles at all times. Immediately clean all spills. If you do get either of these in your eye, immediately flush with water. Your laboratory manual has an extensive list of safety procedures. Read and understand this section.Your laboratory manual has an extensive list of safety procedures. Read and understand this section. Ask your instructor if you ever have any questions about safety.Ask your instructor if you ever have any questions about safety.SAFETY

Harris, D.C Quantitative Chemical Analysis, 5th ed. New York, NY: W.H. Freeman Company.Harris, D.C Quantitative Chemical Analysis, 5th ed. New York, NY: W.H. Freeman Company. McMurry, J., R.C. Fay Chemistry, 4th ed. Upper Saddle River, NJ: Prentice Hall.McMurry, J., R.C. Fay Chemistry, 4th ed. Upper Saddle River, NJ: Prentice Hall. Merriam-Webster, Inc Websters 9th New Collegiate Dictionary. Springfield, MA: Merriam-Webster, Inc.Merriam-Webster, Inc Websters 9th New Collegiate Dictionary. Springfield, MA: Merriam-Webster, Inc. Petrucci, R.H General Chemistry Principles and Modern Applications, 4th ed. New York, NY: Macmillan Publishing Company.Petrucci, R.H General Chemistry Principles and Modern Applications, 4th ed. New York, NY: Macmillan Publishing Company. San José State University Photometric Determination of Manganese in Steel. Available: [accessed 22 February 2007].San José State University Photometric Determination of Manganese in Steel. Available: [accessed 22 February 2007]. Specialty Steel Industry of North America SSINA: Stainless Steel: About. Available: [accessed 12 October 2006].Specialty Steel Industry of North America SSINA: Stainless Steel: About. Available: [accessed 12 October 2006]. Tro, NJ Chemistry, A Molecular Approach. Upper Saddle River, NJ: Prentice Hall.Tro, NJ Chemistry, A Molecular Approach. Upper Saddle River, NJ: Prentice Hall.SOURCES