Iron by 1,10 Phenanthroline Assay Student
Iron by 1,10 Phenanthroline Assay Student
Iron by 1,10 Phenanthroline Assay Student
(aq) 2Fe
2+
(aq) + N
2
(g) + 4H
2
O(l)
Equipment and materials
burettes x 3
1 cm
3
pipette
2 cm
3
pipette
100 cm
3
volumetric flask x 7 (or re-use
one flask)
colorimeter and suitable filter (green)
a solution of the complex displays
maximum absorption at 510 nm
iron(II) ammonium sulfate solution containing
0.100 g dm
3
Fe
2+
(100 ppm), (15 cm
3
)
hydroxylamine hydrochloride solution (if used), 1.5
mol dm
3
(7 cm
3
)
1,10-phenanthroline solution, 5 x 10
3
mol dm
-3
(105 cm
3
)
sodium ethanoate solution, 1 mol dm
3
(14 cm
3
)
solution of unknown Fe
2+
concentration,(15 cm
3
)
Method
Care: Wear eye protection. Hydroxylamine hydrochloride solution is harmful.
1. Fill two burettes, one with the standard iron(II) solution and one with deionised water.
2. Label six 50 or 100 cm
3
beakers A to F and use the burettes to add the solutions shown in the
table:
2
Volumetric flask A B C D E F
Volume of standard iron(II) solution / cm
3
5.0 4.0 3.0 2.0 1.0 0.0
3. To each volumetric flask, use a 1 or 2 cm
3
pipette to add 1.0 cm
3
of 1.5 mol dm
3
hydroxylamine hydrochloride solution (if used) and 2.0 cm
3
of 1 mol dm
-3
sodium ethanoate
solution. From a burette add 15.0 cm
3
of 5 x 10
3
mol dm
3
1,10-phenanthroline solution. Make
up the volume to 100 cm
3
using distilled or deionised water.
Beaker A B C D E F
ppm iron 5 4 3 2 1 0
4. Mix each solution well and leave to stand for 10 minutes.
5. Measure the absorbance of each solution. If the colour of the solutions is too intense for the
colorimeter to measure, dilute the solution by adding more water to the beakers from the
burette and measure the absorbance of the diluted solutions.
6. Plot a graph of absorbance (y axis) against Fe
2+
(aq) concentration (in ppm iron) (x axis) for
beakers A-F.
7. Using a burette, add 10 cm
3
of the iron(II) solution of unknown Fe
2+
concentration to a 100 cm
3
volumetric flask. Use a 1 or 2 cm
3
pipette to add 1.0 cm
3
of 1.5 mol dm
3
hydroxylamine
hydrochloride solution (if used) and 2.0 cm
3
of 1 mol dm
3
sodium ethanoate solution. From a
burette add 15.0 cm
3
of 5 x 10
3
mol dm
-3
1,10-phenanthroline solution. Make up the volume to
100 cm
3
using distilled or deionised water.
8. Measure the absorbance of the solution made up using of the iron(II) solution whose
concentration is unknown.
9. Use the graph to find the concentration of Fe
2+
(aq) as ppm iron in the unknown. Remember
that the iron(II) solution has been diluted ten-fold in the volumetric flask.