Rapid measurement of the content of manganese (carbon, phosphorus, copper, nickel, vanadium, chromium, boron, sulfur) by UV-1100 spectrophotometry

Rapid determination of manganese (carbon, phosphorus, copper, nickel, vanadium, chromium, boron, sulfur) in steel by spectrophotometry

Rapid determination of manganese (carbon, phosphorus, copper, nickel, vanadium, chromium, boron, sulfur) in steel by spectrophotometry. Objectives (1) To understand the principle and method of determining the manganese content in steel by spectrophotometry; (2) Proficiency in the use of spectrophotometer, further training the correct use of pipettes and volumetric flasks; (3) Practice mapping method Process experimental data. 2. Experimental principle A steel of known quality is dissolved in a mixed acid consisting of nitric acid, sulfuric acid and phosphoric acid. Fe+6HN03 = Fe(N03)3+3NO2 十+3H20Mn+4HN03 = Mn(N03)2+2N02 十+2H20Fe3++2H3PO4 = H3[Fe(P04)2] +3H+Ag+2Mn2++5S2O82-+ 8H20 = 2MnO4-+10SO42-+16H+ The obtained MnO4-solution, using a blank sample as a reference solution, can be measured by a spectrophotometer at a wavelength of 530 nm. A series of known concentrations of Mn04-standard solution were treated in the same manner as above, and their absorbances were measured with a spectrophotometer. Taking the absorbance (A) as the ordinate and the standard solution concentration (c) as the abscissa, the relationship between A and c is obtained, which is called the working curve. Through the working curve, the concentration corresponding to the absorbance of the sample solution can be found, and then the content of manganese in the steel sample can be converted. Instruments and reagents: Spectrophotometer V-1100 spectrophotometer, analytical balance, volumetric flask (50mL), pipette (10mL), pipette (5mL), dropper, ear wash, alcohol lamp. Reagents: Mixed acid of HN03-H2S04-H3P04 (1:1:1) 1% AgN03, KMn04 standard solution (containing Mn 1 mg·mL-1), (NH4)2S2O8 (15%), steel. 4. Experimental contents (1) Preparation of standard KMn04 series solution: Pipette 10 mL of standard KMnO4 solution into a 100 mL volumetric flask and dilute to the mark with deionized water. Shake the cap and shake it for use. Also take 6 50ml volumetric flasks. Add each volumetric flask according to Table 5-4, and add the standard KMn04 solution, mixed acid, (NH4)2S2O8 and AgN03 with pipette (or pipette), dilute to the mark with deionized water, and cover the bottle. Shake well after plugging. (2) Treatment of steel sample and preparation of steel sample solution: Accurately weigh a steel sample (60-80 mg) with an analytical balance, place it in a 50 mL beaker, add 17 mL of mixed acid, and heat it in a fume hood with a low temperature potential plate. To dissolve the steel sample, when the brown N02 gas is no longer produced, add 10mL (NH4)2S2O8 and 3mL AgN03 solution, and continue to heat to boiling. Heating can be stopped after boiling for 1 min. After the solution is cooled to room temperature, transfer it to a 50 mL solution bottle, dilute to the mark with deionized water, cover with a stopper, and shake well. (3) Determination of absorbance of the solution: adjust the wavelength of the spectrophotometer to 530 nm (Usage method) See Chapter 2, Section 2.4), using a 0.5cm cuvette to store the test solution, and using a blank sample as the reference solution, determine the absorbance of the five standard KMnO4 solutions and the steel sample solution. 5. The data processing takes the absorbance of the solution as the ordinate and the KMn04 concentration as the abscissa, and makes the Ac relationship working curve of the standard series solution on the coordinate paper. From the absorbance of the steel sample solution, the corresponding concentration is found on the working curve, and the manganese content in the steel sample is calculated.