Experiment #6, Manganese
Notes:
Preparation
• Dry MnSO4⋅H2O for 30 minutes in the 125 °C oven.
• This experiment is highly compatible with the Fluoride experiment for multiplexing your time.
Pre-Lab Calculations
• Standard addition calculations can be confusing at first. You may wish to plot
Absorbance vs. “Added Mn (mg/mL)” for your calibration curve.
Experiment
• Weight 0.20 – 0.22 g KIO4.
• Make sure that all of the KIO4 is dissolved before proceeding.
• Crush larger particles, swirl the flask periodically until no KIO4 particles are visible.
• Allow 5 – 10 minutes more time, swirling occasionally.
• Total dissolution time will be at least 15 minutes.
• A correct blank solution is vital for standard addition methods.
• If you seen a brown tinge in your KMnO4 solutions some irreversible reduction has occurred. You will
need to re-prepare the solution. Possible causes are dirty glassware, residual soap or over-cooking.
• You may divide this experiment into two parts:
• Day 1: Boil the unknown and standard solutions in KIO4, let flasks cool and cover with parafilm.
• Day 2: Finish the experiment.
Review Question
Reminder: This review question is not required – it is designed to extend your knowledge
about the experiment at hand. Other common applications of standard addition methods
include spiking a 5 – 100 mL sample with a very small volume (10 – 100 µL) of a
concentrated standard. These methods rely on having a negligible dilution due to the
added standard. Design an experiment where you would analyze trace Mn levels by
standard addition. Assume 100 ppb – 100 ppm Mn with 10 mL of sample available.
Assume that you can reproducibly deliver 10 µL of “spike” solution. What concentration
of Mn do you need in this solution to analyze a sample of 1 ppm Mn? 10 and 100 ppm?
How precise does the spectrometer need to be?
Pre-Lab Calculation:
The answer is: ____________ (include units)