Page 51 - Practical book PC406-MNU-2025

MANSOURA NATIONAL UNIVERSIY
PHARM D- CLINICAL PHARMACY LEVEL II INSTRUNENTAL ANALYSIS (PC 406)

III- Colorimetric determination of FeCl3

P Pr ri in nc ci ip pl le e

3+
 The colorimetric determination of FeCl 3 depends on the reaction between Fe
and potassium thiocyanate that yields a blood-red colored Ferric-thiocyanate

complex which can be determined colorimetrically at max 470 nm.

-3
+3
-
Fe + 6 SCN → [Fe(SCN)6]
Blood-red colored complex

P Pr ro oc ce ed du ur re e

1) Transfer 2.0, 4.0, 6.0, 8.0, 10.0 mL of standard FeCl 3 solution and 10.0 mL of

the sample solution into 100-mL measuring flasks .

2) To each flask add 1 mL conc. HNO3 and 2 mL of potassium thiocyanate

solution.

3) Dilute to the mark with water and mix well.

4) Measure the absorbance at max 470 nm and draw the standard calibration curve.

5) From the calibration curve determine the unknown concentration of the sample

and calculate a, 1% , ε.
 cm 1
** N.B: - Concentration of the standard FeCl3 solution = 20 mg%
- Molecular weight of FeCl3 = 162.2 gm.

23 | P a g e S e c o n d s e m e s t e r 2 0 2 4 - 2 0 2 5