EXPERIMENT 5

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EXPERIMENT 5

• PREPARATION AND ANALYSIS OF A COMPLEX SALT OF IRON

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PURPOSE

• To prepare and purify an iron-oxalate complex and
  to analyze for the oxalate content using a redox
  titration technique.

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Part I Preparation and Recrystallization of the
Iron Oxalate Complex

• This part will be completed in the same week as
  Experiment 4.
• Your product will be stored by your TA and
  returned to you in your next lab period when you
  complete Part II, the analysis of the compound.
• Be sure to record all data for Part I on the DO
  sheet and be sure to bring it with you to your
  next lab period.

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To one beaker add about 3.20 g of FeCl3.6H2O.
Record the exact weight.
Take two labeled 50 mL beakers to the top-loading
balance.
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To the other beaker add about 12.00 g of
K2C2O4.H2O. Record the exact weight.
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Add 8.0 mL of H2O to the beaker containing
FeCl3.6H2O.
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Stir to dissolve the solid, gently warming the
mixture if necessary.
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Set this solution aside.
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Add 8.0 mL of H2O to the beaker containing
K2C2O4.H2O.
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Warm gently to dissolve the solid.
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Then heat the solution to about 80 oC.
ATTENTION! Do not stir with the thermometer, but
with the stirring rod!
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Remove the oxalate solution from the heat and set
it on a paper towel on the bench top.
Carefully add the hot solution of K2C2O4.H2O to
the iron solution.
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Allow the solution to cool so that crystals form
and the solution is close to room temperature.
Do not move it or stir it while it is cooling!
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Leave the mixture on ice for approximately 5
minutes. During this time the new iron-oxalate
compound will precipitate.
Place the beaker in ice water and let the
solution cool to 5 oC (1 oC).
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In the meantime chill a 5 mL sample of distilled
H2O and a 10 mL sample of acetone in separate,
labeled test tubes.
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Decant (pour off) as much of the supernatant
liquid as possible, leaving the wet solid in the
beaker.
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To recystallize the product, add 20 mL of
distilled H2O.
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As before cool to near room temperature, then
place in ice water for approximately 5 minutes,
during which time crystals of the pure
iron-oxalate compound will form.
Heat (40 50 oC) and stir to completely dissolve
the green compound.
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Collect the product by vacuum filtration.
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Use the rubber policeman to transfer as much
compound as possible.
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Wash the product first with small portions of the
5 mL ice cooled distilled H2O.
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And then with small portions of the 10 mL of cold
acetone.
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Leave the solid product on the filter paper, with
the suction on, for about 5 minutes to complete
the drying process.
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Pre weigh the large glass vial on the top-loading
balance (record the weight).
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Carefully transfer the product to the vial then
re-weigh the vial product. Record these data.
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Hand in your sample to your TA who will return it
to you in your next lab period when you do Part
II.
Cover your vial with a piece of filter paper held
on with an elastic band.