Determination of Manganese in Steel Submitted by: ------------------- Date of Submission: 27. 03. 11 Objectives: In steel production aside the iron, which is the primary source, some amounts of manganese is used together with carbon. The objective of this experiment is determining the manganese amount in the steel compound by using UNICAM UV-VIS Spectrometer. Theory: Many molecules absorb ultraviolet or visible light. The absorbance of a solution increases as attenuation of the beam increases.
Absorbance is directly proportional to the path length, b, and the concentration, c, of the absorbing species. Beer's Law states that A = ebc, where e is a constant of proportionality, called the absorptivity. Different molecules absorb radiation of different wavelengths. An absorption spectrum will show a number of absorption bands corresponding to structural groups within the molecule. In this experiment wavelength range between 400-650nm is used in order to detect in the visible range. Steel is an alloy primarily composed of iron with carbon content between 0. 2% and 1. 7% by weight. 1. 5% manganese is may be used too, to provide additional strength for a modest price increase. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another. Manganese is essential to iron and steel production by virtue of its sulfur-fixing, deoxidizing, and alloying properties. In order to detect the manganese amount in the compound KIO4 is used to oxidize Mn+2 to Mn +7 since Mn+2 does not absorb in the visible region therefor cannot be detected.
Tungsten lamp is used in the experiment to reach the range between 400-650nm. After the beam comes from the tungsten lamp, it passes through the monocromator to reach the wavelength range which was selected to find the maximum wavelength. After the light passes through the monocromator it goes through the cuvette and then the detector. The cuvette is made of quartz in order to pass the visible light whereas a glass cuvette would absorb it. The Redox Reaction: 5 IO4 - + 2 Mn2+ + 3 H2O ? 2 MnO4 + 5 IO3- + 6 H+ Reagents: KMnO4 KIO4 H3PO4 Unknown Solution
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Deionized Water Apparatus: Pipette Beaker Heater UNICAM UV-VIS Spectrometer Quartz Cuvette Volumetric Flask Calculations: Weight of KMnO4 : 0. 09149g Weight of KIO4 : 0. 40807g emax: 525nm Absorbance for the unknown: 0,415 [pic] Conclusion: I: Qualitative and or Quantitative identification II: Error discussion While at the addition step of H3PO4 after 5ml of H3PO4 is pipetted, it was transferred into a volumetric cylinder, and then transferred into the unknown solution and the blank solution. There may have been material loss during the process.
Dilution errors may have been done during the dilution process. There may be some personal errors made while weighing the compounds Any scratch, stain or fingerprint left on the cuvette may cause a shift from the accurate wavelength in the detected value. If any bubbles left in the cuvette while the detection is made will as well as cause wrong wavelength value. Reference: http://teaching. shu. ac. uk/hwb/chemistry/tutorials/molspec/uvvisab1. htm http://www. kimya. boun. edu. tr/webpages/courses/chem308/Determination%20of%20Manganese%20in%20Steel. pdf
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