HIRANUMA APPLICATION DATA

Automatic Titrator

Data No.

O9Feb. 03,
2022

Standardization of ammonium
iron(II) sulfate titrant

Factorstandardization
1. Abstract

Ammonium iron (II) sulfate is a reducing agent and is used as a titrant in redox titration because it has
relatively stable properties among iron (II) compounds. The following are examples of usage: first, anexcessive amount of potassium permanganate is added to react with target metal compound, such as chromiumor vanadium, contained in the sample. Next, the potassium permanganate that remains unreacted is titrated withan ammonium iron(II) sulfate standard solution to indirectly quantify the target metal compound.
In the above example, 5 mol of ammonium iron (II) sulfate reacts quantitatively with 1 mol of potassium
permanganate by the formula (1), and this reaction is also used for the standardization of iron (II) ammonium
sulfate.
JIS K8001 and the Japanese Pharmacopoeia describe that the ammonium iron (II) sulfate standard
solution to be standardized is taken into a titration vessel and the titration is performed with potassium
permanganate standard solution. The titration curve shows an inflection point at the endpoint.
10FeSO4 ＋ 8H2SO4 ＋ 2KMnO4 → K2SO4 ＋ 2MnSO4 ＋ 5Fe2(SO4)3 ＋ 8H2O･･･(1)1) Japanese Pharmacopoeia Eighteenth Edition
2) Japanese Industrial Standard JIS K8001 General rules for test methods of reagents

2. Configuration of instruments and reagents(1) Configuration of instruments
Main unit
Electrodes: Automatic Titrator

COM Series

Optional buret

1 unit: Platinum electrodePT-301

Reference electrodeRE-201Z* It can also be applied to combinations of other platinum electrodes such as
PR-701BZ.
(2) ReagentsStandard solution : 0.02 mol/L (0.1 N) potassium permanganate standard solution(f = 1.000, Buret No. 2), Used as a titrant
Sample to be standardized: 0.1 mol/L (0.1 N) ammonium iron (II) sulfate standard solution(Buret No.1), Used as a sample
Additive reagent: Phosphoric acid, Guaranteed reagent

3. Measurement procedure(1) Add 40 mL of DI water, 5 mL of phosphoric acid, and a stirrer bar to a 100 mL beaker.
(2) Immerse the electrodes and start the measurement. 10 mL of 0.1 mol/L ammonium iron (II) sulfate
standard solution is added to the beaker by the buret dispensing.
(3) Titration is subsequently performed with 0.02 mol/L potassium permanganate standard solution. The
inflection point on the titration curve is detected as the end point.

4. Measurement conditions and results
Examples of titration conditions
M. File1+2
Cndt No.
1
MethodDisp
Buret No.
1S-Timer
5 sec
Disp Vol.
10 mL
Cndt No.
2
MethodAutoConstantNo.
2
Buret No.
2Size
10 mL
Amp No.
2Blank0 mL
D. UnitmVMolarity
0.1 mol/L
S-Timer
5 sec
Factor1.000 *1C.P. mL
0 mL
K0T Timer
0 sec
L0D.P. mL
1.0 mLEnd Sens
200
Unit
Fact(D-B)/S*F
Over mL
0.5 mL
FormulaMax.Vol.
20 mL
Digits4*1: Factor of 0.02 mol/L potassium permanganate standard solution

Mode No.
Pre Int
Del K
Del Sens
Int TimeInt Sens
Brt Speed
Pulse

40903
3240

Measurement results
Measurement
No.
123Sample
size (mL)
1010
10

Titrant
volume (mL)
10.27510.27410.271

Factor
1.02751.0274
1.0271

Statistic calculation
Avg.
SD
RSD

1.027
0.00020.02 %secmV
secmV

Examples of titration curves

5. Note(1) About the factor calculation formula of the ammonium iron (II) sulfate standard solution
In measurement of the factor standardization, there are many case examples of titrating a standard materialusing the titrant to be standardized. In the procedure of JIS K8001 and Japanese Pharmacopoeia for ammonium
iron (II) sulfate standard solution, the titrant and the sample are reversed. The potassium permanganate
standard solution is used as the titrant, and the ammonium iron (II) sulfate standard solution to be standardized
is used as the sample for titration.
In this case, the factor calculation formula is set as [(D-B)/S*F]. This formula is not initially installed in thetitrator and must be set using the formula editing function.
The calculation formula is derived based on the following relational formula (2). The left side (subscript s) isthe titrant of potassium permanganate standard solution and has already been standardized preliminary, and theright side (subscript t) is the sample of ammonium iron (II) sulfate standard solution to be standardized.
ns × Ms ×Fs × (D - B) = nt × Mt × Ft × S
Potassium permanganate

・・・(2)

Ammonium iron (II) sulfate

ns：Valence (5)nt：Valence (1)Ms：Molar concentration (0.02)

Mt：Molar concentration (0.1)

Fs：Factor (Known)

Ft：Factor (Unknown)

D-B：Titrant volume (mL)

S：Sample size (mL)

Keywords：Factor standardization, Redox titration, Ammonium iron (II) sulfate, Potassium permanganate*Some measurement would not be possible depending on optional configuration of system.