HIRANUMA APPLICATION DATA

Data No.

Automatic Titrator

G6Apr. 5,
2019

Determination of ferrous and ferric ion insteel cleaning solution

Metals
1. Abstract

A wide variety of the determination methods for each component in acidic solution containing ferrous ion
2+(Fe ) and ferric ion (Fe3+) has been developed. This report introduces an example of the successive
determination for ferric and ferrous ions in the steel cleaning solution.
First, Fe3+ ions are determined by chelatometric titration with EDTA at acidic pH using salicylic acid as
the indicator (purple →yellow). The all Fe2+ ions are continuously oxidized to Fe3+ ion with ammonium
peroxodisulfate. Finally, the Fe3+ ion oxidized from Fe2+ is determined by chelatometric titration with EDTA
titrant as well as the above description.

Fe3+
Fe2++ Na2EDTA→
Fe3+ +→

FeEDTA+2Na+e-2. Configuration of instruments and reagents(1) Configuration of instruments
Main unit: Hiranuma Automatic Titrator

COM Series(M type photometric unit for photometric titration with 530 nm optical filter)(2) Reagents
Titrant: 0.1 mol/L EDTA standard solutionOxidizing solution : Ammonium peroxodisulfate (Ammonium persulfate)
Indicator reagent: 2 % salicylic acid in ethanol solution

3. Measurement procedure(1) Dispense 1 mL of sample into a 100 mL tall beaker with volumetric pipette.
(2) Add 60 mL of DI water.
(3) Add 0.2 mL of 2 % salicylic acid in ethanol solution.
(4) Immerse photometric probe and start titration with EDTA standard solution.
(5) After the endpoint for Fe 3+ ion is detected, add approximately 1 g of ammonium peroxodisulfate
during waiting time (S. Timer, 120 sec) to oxidize Fe2+ to Fe3+ ion.
(6) Continuously titrate with EDTA standard solution.

4. Measurement conditions and results
Example of titration condition(1) Titration for Fe3+ ion
Cnd. No.

1Method

AutoConstant No.

1Mode No.

5Buret No.

1Size

1 mL

Pre Int0 sec

Amp No.

2Blank

0 mL

Del K

5D.UnitT%

0.1 mol/L

Del Sens

0 mV

S- Timer

5sec

Factor

1.008

Int Time

3 sec

C.P. mL

0mL

K

55.85

Int Sens

3 mVT.Timer0sec

L0Brt Speed

2D.P. mL

0mL

Unitg/L

Pulse40End Sens

500

Over mL

0Max Vol.

20 mL

Molarity

FormulamL(D-B)*K*F*M/S
Decimal Places

3Auto input parameter

None(2) Titration for Fe2+ ion
Cnd. No.

2Method

AutoConstant No.

2Mode No.

5Buret No.

1Size

1 mL

Pre Int

0Amp No.

2Blank

0 mL

Del K

5D.UnitT%

Molarity

0.1 mol/L

Del Sens

0mV

S- Timer

120 sec

Factor

1.008

Int Time

3sec

C.P. mL

0mL

K

55.85

Int Sens

3mV

T.Timer

0sec

L0Brt Speed

2g/LPulse

40D.P. mL

0.3 mL

UnitEnd Sens

500

FormulaOver mL

1Max Vol.

20 mL

mL(D-B)*K*F*M/S
Decimal Places
Auto input parameter

3None*Some measurement would not be possible depending on optional configuration of system.

secMeasurement results
Number ofSize

Titrant

Fe3+ ion

Titrant

Fe2+ ion

Measurement(mL)

Volume (mL)Concentration (g/L)

Volume (mL)Concentration (g/L)

1

1

4.178

23.5219.406

52.953

2

1

4.162

23.4319.454

53.223

3

1

4.220

23.7579.537

53.690Statistic
calculation

Avg.

23.6 g/L

53.3 g/L

SD

0.168 g/L

0.373 g/L

RSD

0.71 %

0.70 %

Example of titration curve

5. NoteThe following tips could improve measurement accuracy.
(1) Successive titration of Fe3+ and Fe2+ ions
The stability constant of EDTA Chelate for Fe2+ ion is low at acidic pH, thus this method utilize the property
that the coexisting Fe3+ ion can selectively be reacted with EDTA. The applicable pH region is 2 ~ 3.
(2) Oxidizing agent for Fe2+ ion
Ammonium peroxodisulfate is used as oxidizing agent for Fe2+ ion in this report, but hydrogen peroxide is alsousable instead. In either case, please note that the excessively added reagents are likely to generate air bubbles
which interfere the photometric titration.
Keywords: Ferrous (Fe2+) ion, Ferric (Fe3+) ion, Chelatometric titration, EDTA, Photometric titration*Some measurement would not be possible depending on optional configuration of system.