HIRANUMA APPLICATION DATA

Data No.

Automatic Titrator

O5Feb. 03,
2022

Standardization of ammonium
thiocyanate titrant

Factorstandardization
1. Abstract

The measurement method of chloride ions or salt content by precipitation titration using a silver nitrate
standard solution is widely used in the titration method. The back-titration method of silver nitrate titration isused for some substances listed in the Japanese Pharmacopoeia. The back-titration method is generally applied
when the titration reaction is slow, and the reaction progresses faster than a forward titration by adding an
excessive amount of titrant to the sample. An excessive amount of silver nitrate standard solution is added tothe sample to react with the target component in the sample, and the remaining silver nitrate is titrated withammonium thiocyanate standard solution to indirectly quantify the target component in the sample.
This report introduces the factor determination method for ammonium thiocyanate standard solution.
Firstly, 0.1 mol/L silver nitrate standard solution, which is a standard material, was dispensed with a buret.
Secondly, potentiometric titration was performed with ammonium thiocyanate standard solution to determine
the factor of ammonium thiocyanate. 1 mol of silver nitrate and 1 mol of ammonium thiocyanate react
quantitatively according to formula 1, and the titration curve shows an inflection point at the end point.
NH4SCN ＋ AgNO3 → AgSCN↓ ＋ NH4NO3･･･(1)Japanese Industrial Standard (JIS K8001) and the Japanese Pharmacopoeia describe that standardized
silver nitrate solution should be used for factor determination of ammonium thiocyanate standard solution. See
Application Data No. O4 for the method of standardizing silver nitrate standard solution.
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: Silver-reference combination electrode

AGR-811Z** It can also be applied to combinations of other silver electrodes such as AG-311
and silver comparison electrodes such as RE-241Z.
(2) Reagents
Titrant: 0.1 mol/L (0.1 N) ammonium thiocyanate standard solution (Buret No. 2)Standard sample: 0.1 mol/L (0.1 N) silver nitrate standard solution (f = 0.995, Buret No.1)

3. Measurement procedure(1) Add 50 mL of DI water and a stirrer bar to a 100 mL beaker.
(2) Immerse the electrodes and start the measurement. 10 mL of silver nitrate standard solution is added tothe beaker by the buret dispensing.
(3) Titration is subsequently performed with a 0.1 mol/L ammonium thiocyanate standard solution. The
inflection point on the titration curve is detected as the end point.

4. Measurement conditions and results
Examples of titration conditions
Factor standardization measurement of 0.1 mol/L ammonium thiocyanate standard solution

M. File1+2Cndt No.
1Method
DispBuret No.
1S-Timer
5 sec
Disp Vol.
10 mL
Cndt No.
2Method
AutoConstantNo.
2Buret No.
2Size
10 mL
Amp No.
2Blank0 mL
D. UnitmV
Molarity
0.1 mol/L
S-Timer
5 sec
Factor
0.995 *1
C.P. mL
0 mL
K
0T Timer
0 sec
L
0D.P. mL
1 mL
End Sens
500
Unit
Fact1
Over mL
0.5 mL
FormulaS/(D-B)*F
Max.Vol.
20 mL
Digits
4*1: Factor of 0.1 mol/L silver nitrate standard solution

Mode No.
Pre IntDel K
Del Sens
Int Time
Int Sens
Brt SpeedPulse

40
903
3
240

Measurement results
MeasurementNo.
1
2
3Samplesize (mL)
1010
10

Titrant
volume (mL)
9.973
9.980
9.984

Factor
0.99770.99700.9966

Statistic calculation
Avg. 0.997
SD0.001
RSD 0.06 %secmV
secmVMeasurement of factor of ammonium thiocyanate standard solution

Examples of titration curves

5. Note(1) About the buret for dispensing silver nitrate
In this report, silver nitrate standard solution was dispensed and then immediately titrated with ammonium
thiocyanate standard solution. For some substance described in the Japanese Pharmacopoeia, back-titration
with silver nitrate and ammonium thiocyanate is applied for a quantitative method of its purity. These methods
are described in which an excessive amount of silver nitrate is dispensed, allowed to stand the solution
overnight, filtered it, and then titrated with an ammonium thiocyanate standard solution. In that case, use
dispensing function of the buret or use a volumetric pipette to add a certain amount of silver nitrate to thesample precisely.
Keywords：Factor standardization, Precipitation titration, Back-titration, Silver nitrate, Ammonium thiocyanate*Some measurement would not be possible depending on optional configuration of system.