CHEM 297 INTERMEDIATE CHEMISTRY II LABORATORY
WEEKS OF FEBRUARY 21 AND 28
INORGANIC COMPLEX SYNTHESIS AND ANALYSIS
POTASSIUM TRIS-OXALATOFERRATE (III) TRIHYDRATE
K3[Fe(C2O4)3].3H2O
SYNTHETIC PROCEDURE
2FeCl3 + 6K2C2O4.H2O  2K3[Fe(C2O4)3].3H2O + 6KCl + 3H2O
Add 8 mL of 2.5 M FeCl3 solution to a hot solution containing 12 g of K2C2O4.H2O in 20 mL of water.
Cool the solution to 0oC and keep it at 0oC until crystallization is complete. Decant the mother liquor
carefully and redissolve the yellow-green crystals in 20 mL of warm water. Cool again to 0 oC, collect the
crystals by vacuum filtration, and wash them with a small volume of ice-cold water. Air-dry the product in
the dark, as it is photosensitive.
ANALYSIS
1. Iron (III)
Weigh out a sample of the compound in the range of 0.0600 g and place it in a tall form beaker. Do all the
following in the fume hood. Dissolve the sample in several mL of concentrated H 2SO4. Heat the mixture
on a hot plate until the fumes of SO3 are just detected. CAUTION: H2SO4 is a very strong acid. SO3
fumes should not be inhaled. Let the mixture cool and then add with extreme caution 5 mL of concentrated
HNO3. This step is potentially dangerous so take adequate precautions against spattering or spilling.
Evaporate the mixture slowly to dryness and avoid charring the organic material that may remain. Do all
the above in the hood.
Dissolve the residue in 20 mL of 0.02 M HCl, filter any remaining particulate matter, add 3 mL of 1%
salicylic acid solution and dilute quantitatively to 100 mL total volume (volumetric flask).
Determine the absorbance of Fe3+ solutions formed by adding 4 mL of salicylic acid solution to 50 mL of 6
x 10-3M Fe3+ in 0.02M HCl and diluting to 100 mL with 0.02 M HCl to give 3 x 10-3 M Fe. Successfully
dilute this solution with 0.02 M HCl to obtain 1.5 x 10 -3 M, 0.75 x 10-3 M and 0.375 x 10-3 M solutions.
Graph to obtain a calibration curve and use this curve to determine the concentration of your sample. All
readings are taken at 525 nm
Calculate the millimoles of Fe in your original solution, convert to grams of Fe and calculate the % Fe in
your sample.
2. Organic ligand
Obtain the IR spectra of your complex. Assign the major absorptions in the spectrum to the appropriate
bond vibrations.