Dosage du Fer dans l'Eau

Mesure de la concentration en fer dissous par colorimétrie au thiocyanate

Colorimetry Intermediate (High School) 75 min ~$10,00

Objectif

Déterminer la concentration en fer(III) d'un échantillon d'eau par la méthode colorimétrique au thiocyanate.

Contexte

Iron(III) ions react with thiocyanate ions (SCN⁻) to form the intensely red-colored complex [Fe(SCN)]²⁺. The intensity of the red color is proportional to the Fe³⁺ concentration, following the Beer-Lambert law. This method is widely used in water quality testing and environmental monitoring. Students learn both the analytical technique and the chemistry of complex ion formation.

Avertissements de sécurité

  • FeCl₃ solution stains skin and clothing
  • KSCN is harmful if swallowed
  • HNO₃ is corrosive — handle with care
  • Dispose of thiocyanate waste in designated containers

EPI requis

goggles gloves lab_coat

Matériaux

  • Iron(III) chloride (FeCl₃) standard (100 mL)
    0.01 M stock solution
  • Potassium thiocyanate (KSCN) (100 mL)
    0.1 M solution
  • Dilute HNO₃ (0.1 M) (50 mL)
    To maintain acidity
  • Water sample (50 mL)
    Unknown iron content
  • Distilled water (500 mL)
    For dilutions

Équipement

Colorimeter or spectrophotometer Cuvettes (matched pair) Volumetric flasks (50 mL, 7 total) Pipettes (1 mL, 5 mL, 10 mL) Pipette filler

Procédure

1

Prepare a series of standard Fe³⁺ solutions (0, 1, 2, 4, 6, 8, 10 ppm) by diluting the stock FeCl₃ solution in 50 mL volumetric flasks.

15 min
2

Add 5 mL of 0.1 M KSCN and 2 mL of dilute HNO₃ to each standard flask and the water sample. Make up to volume with distilled water.

10 min
3

Allow 5 minutes for full color development. The solutions should range from pale to deep red.

5 min
4

Set the colorimeter to 480 nm. Zero with the blank solution (0 ppm Fe³⁺ + KSCN).

5 min
5

Measure the absorbance of each standard solution and the water sample.

15 min
6

Plot the calibration curve (absorbance vs. concentration). Use it to determine the iron concentration in the water sample.

15 min
7

Calculate the iron concentration and evaluate whether the water meets drinking water standards (<0.3 ppm).

10 min

Résultats attendus

The calibration curve should be linear from 0 to 10 ppm. The deep red color of [Fe(SCN)]²⁺ intensifies with increasing Fe³⁺ concentration. The water sample's iron content is determined from the calibration curve.

Nettoyage

Collect all thiocyanate-containing solutions in labeled waste. Rinse all glassware thoroughly. Wipe down the colorimeter.

Détails

Catégorie
Colorimetry
Difficulté
Intermediate (High School)
Durée
75 min
Coût estimé
$10,00
Étapes
7
Matériaux
5

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Frequently Asked Questions

What is the objective of Dosage du Fer dans l'Eau?
Déterminer la concentration en fer(III) d'un échantillon d'eau par la méthode colorimétrique au thiocyanate.
How difficult is Dosage du Fer dans l'Eau?
This experiment is rated as Intermediate (High School). It takes approximately 75 minutes to complete.
What safety precautions are needed for Dosage du Fer dans l'Eau?
Key safety precautions include: FeCl₃ solution stains skin and clothing; KSCN is harmful if swallowed; HNO₃ is corrosive — handle with care.
What materials are needed for Dosage du Fer dans l'Eau?
The main materials required are: Iron(III) chloride (FeCl₃) standard, Potassium thiocyanate (KSCN), Dilute HNO₃ (0.1 M), Water sample, Distilled water.
What results should I expect from Dosage du Fer dans l'Eau?
The calibration curve should be linear from 0 to 10 ppm. The deep red color of [Fe(SCN)]²⁺ intensifies with increasing Fe³⁺ concentration. The water sample's iron content is determined from the calibration curve.