1. Colorimetric Determination of Iron
Experiment 33
Colorimetric Determination of Iron
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2. In Lab
Work in groups of 4
2 people do part A; preparing the standard solutions
2 people do part B; preparing the 3 trials of the one unknown sample
Everyone makes their own calibration curve and determines the concentration of %Fe in the unknown sample
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3. Part A Prepare all solutions at the same time
Prepare a blank solution (no Fe)
Allow only 15 minutes for color development
Use disposable test tubes instead of cuvettes for use in the spectrophotometer
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4. Part B Prepare all solutions at the same time
Follow some of Part A procedure (no Fe)
Share the blank solution (no Fe) from Part A
Allow only 15 minutes for color development
Use disposable test tubes instead of cuvettes for use in the spectrophotometer
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5. Spectrophotometer (Parts A and B)
An instrument that will indicate the amount of light (of one wavelength) absorbed by a sample
readout
detector
sample
monochromator
Light source
slit
LED readout
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6. Making the Calibration Curve
You will acquire an absorbance reading for each standard solution prepared (share data)
Use the data from Part A to construct the calibration curve
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7. Calibration Curve
Concentration, mg Fe / mL (x10-3)
Absorbance
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8. Using the Calibration Curve to Find Concentration of the Unknown Solution
Absorbance
Unknown solution absorbance reading
Concentration of unknown solution
Concentration, mg Fe / mL (x10-3)
Show this on your graph
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9. For All Students Typing error on x axis of graph paper:
mg Fe / mL (x 10 -3)
Typing error on y axis; should be Absorbance
Calculating % Fe in unknown sample:
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10. mg/mL of original sample
You will know the grams of original sample from the balance readout, and you will know the dilutions made during sample preparation:
grams converted to mg
mg divided by size of first volumetric flask, in mL
1 mL diluted by size of second volumetric flask, in mL
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