A rapid Method for the Determination of Iodine with Potentiometric

A rapid method for the Determination of Iodine with Potentiometer

Equipment
Potentiometer = 751 GPD Titrino / Titroprocessor
Electrodes = 6.0431.100 Pt Titrode; input 1

Reagents
c(Na₂S₂O₃) = 0.1 mol/L; D0

Sample
3 mL c(KI₃) = 0.05 mol/L
5 mL c(H₂SO₄) = 0.5 mol/L
20 mL dist. Water

Remarks
· Determination reaction:

I₂ + 2 S₂O₃^2- → 2 I ^- + S₄O₆^2-

· Calculations:

c(KI₃)=EP1*C01/C02/C00;4;mol/L

c(KI₃) = concentration of KI₃ solution in mol/L
C01 = concentration of titrating agent (0.1 mol/L)
C02 = factor for “normality“ (2)

· Titrate samples immediately.

. Answer

c(KI₃)=2.997x0.1/2/3=0.0499 mol/L

EP1=2.997 mL
C00=3 mL

Literature
Metrohm’s Teachware on CD-ROM

Method documentation
'pa
751 GPD Titrino 15215 751.0010
DET U Iodine
parameters
>titration parameters
meas.pt.density… 4
min.incr. …10.0 ml
dos.rate max…. ml/min
signal drift …20 mV/min
equilibr.time …38 s
start V: …OFF
pause …0 s
dos.element:… internal D0
meas.input: …1
temperature …25.0 °C
>stop conditions
stop V: …abs.
stop V …5 ml
stop U …OFF mV
stop EP …9
filling rate max…. ml/min
>statistics
status: …OFF
>evaluation
EPC …5
EP recognition:… all
fix EP1 at U …OFF mV
pK/HNP: …OFF
>preselections
req.ident: …OFF
req.smpl size:… OFF
activate pulse: …OFF
------------
'fm
751 GPD Titrino 15215 751.0010
DET U Iodine
>calculations

c(KI3)=EP1*C01/C02/C00;4;mol/l

C00= 3.0
C01= 0.1
C02= 2
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'fr
751 GPD Titrino 15215 751.0010
U(init) -95 mV DET U.... Iodine
smpl size …3.0 ml
EP1 …2.997 ml… 65 mV
c(KI3) …0.0499 mol/l
stop V reached
============
'cu
751 GPd Titrino 15215 751.0010
start V 0.000 ml DET U Iodine
2.0 ml/div dU=50.0 mV/div
============