HIRANUMA APPLICATION DATA

Data No.

Automatic Titrator

N2Feb. 10,
2021

Determination of chloride ionin concrete

CementConcrete
1. Abstract

This report introduces an example of the determination of chloride ion in concrete.
This measurement method is described in "Potentiometric titration method using chloride ion-selective
electrode" of "JIS A 1154 Method of test for chloride ion content in hardened concrete". Nitric acid is added toadjust the pH to 3 or less, and extract chloride ion with boiling. Cool to room temperature, filtrate to separateundissolved component and collect filtrated solution as sample. Chloride ion is determined by precipitation
titration using a silver nitrate standard solution.

Cl- ＋AgNO3→AgCl＋NO3-2. Configuration of instruments and reagents(1) Configuration of instruments
Main unit: Automatic Titrator COM Series

Electrode: Chloride ion-selective electrodeCLi-081 (Connect to IE-2)

Reference electrodeMS-231Z (Connect to RE-2)*Remark
The general reference electrode (RE-201Z) cannot be used for this titration because KCl
inner solution might come out to sample solution and it causes measurement error.
The inner electrodes of MS-231Z use mercury (I) sulfate. When these electrodes aredisposed, please ask the specialized industrial waste disposal operator.

Filter paper: For quantitative analysis(2) Reagents
Titrant: 0.005 mol/L Silver nitrate standard solution

Additive: Diluted nitric acid
Prepared by mixing nitric acid (60 %) in a volume ratio of 1 to 6 in DI water

3. Measurement procedure(1) Take 10 g of sample into a 200 mL beaker and accurately weigh it.
(2) Add 70 mL of diluted nitric acid slowly and stirrer it. Then measure the pH to confirm the pH is 3 or less.
(3) Cover the beaker with watch glass and heat to boil for 5 minute. Then cool it to room temperature.
(4) Filtrate the solution using filter paper with aspirating and wash the filter paper with water.
(5) Collect filtrated solution into a volumetric flask to make it 200 mL with DI water.
(6) Take the solution prepared at (5) with a 50 mL volumetric pipet into a 100 mL beaker.
(7) Immerse electrodes and titrate with 0.005 mol/L silver nitrate standard solution.
*Some measurement would not be possible depending on optional configuration of system.

4. Measurement conditions and results
Example of titration condition
Cnd. No.
MethodBuret No.
Amp No.
D.UnitS- Timer
C.P. mL
T.Timer
D.P. mLEnd Sens
Over mLMax Vol.

1Auto
12mV
5000.1
30
0.5
20sec
mL
sec
mL
mL
mL

Constant No.
1Size
10.0314 gBlank
0 mL
Morality
0.005 mol/L
Factor
1K35.45
L50
Unit%
Formula(D-B)*K*F*M/(S*10)*200/L
Decimal Places
4Mode No.
Pre Int
Del K
Del Sens
Int Time
Int Sens
Brt Speed
Pulse

805053240secmVsecmV

Measurement results
Number ofmeasurement

SampleTitration

Chloridesize (g)volume (mL)ion (%)

2.326

0.01642.340

0.01652.296

0.01621
2

10.03143

Avg.

0.0164 %SD

0.0002 %RSD

0.93 %

Example of titration curve

5. Note・Indicator electrode
Chloride ion-selective electrode was used as an indicator electrode for this measurement.
In addition to the above electrode, a silver electrode coated with silver chloride (model: AG-311A) can also be
used for this measurement. However, since the silver electrode coated with silver chloride deteriorates after
long-term use, the electrode potential change near the end point becomes small and unclear. On the other hand,the chloride ion-selective electrode has the advantage that when the sensitivity deteriorates, the sensitivity canbe easily restored by lightly polishing the sensitive membrane with a sandpaper.
Keywords: Chloride ion, Precipitation titration, Concrete, JIS A1154*Some measurement would not be possible depending on optional configuration of system.