Determination of chloride ion in cement | Autotitrator COM-A19 - JM Science
HIRANUMA APPLICATION DATA Automatic Titrator Data No. N1 Feb. 10,2021
Cement Concrete Determination of chloride ion in cement

1. Abstract

This report introduces an example of the determination of chloride ion in cement.

This measurement method is described in “Method for measuring chloride” of “Japanese industrial standard JIS R 5202 Method for chemical analysis of cements”. The sample is dissolved in nitric acid, a chloride ion standard solution and a hydrogen peroxide solution are added, and the sample is heat-treated, and then the measurement is performed by precipitation titration using a silver nitrate standard solution. The measurements are made by potentiometric titration using a chloride ion-selective electrode as the electrode for end point detection.

Cl⁻ +  AgNO₃  →  AgCl  +  NO₃⁻

2. Configuration of instruments and Reagents

(1) Configuration
  Main unit : Automatic Titrator COM series
  Electrode : Chloride ion-selective electrode CLi-081 (Connect to IE-2)
Reference electrode MS-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 are disposed, please ask the specialized industrial waste disposal operator.
(2) Reagents    
  Titrant : 0.005 mol/L Silver nitrate standard solution
  Additive : Nitric acid (60 %, density 1.38 g/mL)
Hydrogen peroxide (Approx. 30 %)
0.005 mol/L Chloride ion standard solution

3. Measurement procedure

(1) Take 5 g of sample into a 200 mL beaker and accurately weigh it.
(2) Add about 20 mL of DI water. Then add 12 mL of nitric acid with stirring to dissolve the sample.
(3) Add warm DI water to make 100 mL sample solution.
(4) Add 2 mL of chloride ion standard solution with volumetric pipette.
(5) Add 2 mL of 30 % hydrogen peroxide.
(6) Cover the beaker with watch glass and heat to boil for 1-2 minute. Then cool it to room temperature.
(7) Immerse electrodes and titrate with 0.005 mol/L silver nitrate standard solution.
(8) As blank test, take 2 mL of 0.005 mol/L chloride ion standard solution exactly in a 200 mL beaker, add warm DI water to make 100 mL, and perform procedure (6) and (7).

4. Measurement conditions and results

Examples of titration conditions

(1) Measurement of blank

Cndt No. 1
Method Auto
Buret No. 1
Amp No. 2
D. Unit mV
S-Timer 5 sec
C.P. mL 0 mL
T Timer 0 sec
D.P. mL 0.2 mL
End Sens 200
Over mL 0.5 mL
Max Vol. 20 mL
Constant No. 6
Size 0 g
Blank 0 mL
Molarity 0.005 mol/L
Factor 1.001
K 0
L 0
Unit mL
Formula
D
Decimal Places 3
Mode No. 20
Pre Int 0 sec
Del K 2
Del Sens 0 mV
Int Time 5 sec
Int Sens 3 mV
Brt Speed 2
Pulse 80

 

(2) Measurement of sample

Cndt No. 2
Method Auto
Buret No. 1
Amp No. 2
D. Unit mV
S-Timer 5 sec
C.P. mL 0 mL
T Timer 0 sec
D.P. mL 0.1 mL
End Sens 150
Over mL 0.5 mL
Max Vol. 20 mL
Constant No. 7
Size 5.0233 g
Blank 2.062 mL
Molarity 0.005 mol/L
Factor 1.001
K 0
L 0
Unit %
Formula
(D-B)*F*0.01773/S
Decimal Places 4
Mode No. 20
Pre Int 0 sec
Del K 2
Del Sens 0 mV
Int Time 5 sec
Int Sens 3 mV
Brt Speed 2
Pulse 80

Measurement results

Sample Number of
measurement
Sample
Size(g)
Titration
volume (mL)
Chloride ion(%) Statistical
Calculation
BLANK 1   2.055   Avg. 2.062 mL
2 2.078 SD 0.014 mL
3   2.052   RSD 0.69 %
SAMPLE 1 5.0098 6.749 0.0166 Avg. 0.0168 %
2 5.0152 6.825 0.0169 SD 0.0002 %
3 5.0233 6.836 0.0169 RSD 1.03 %

 

Examples of measurement curves

Measurement of blank  Measurement of sample

 

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 can be easily restored by lightly polishing the sensitive membrane with a sandpaper.

Keywords: Chloride ion, Precipitation titration, Cement, JIS R5202

*Some measurement would not be possible depending on optional configuration of system.

Cement concreteHiranuma aquacounter autotitrator com-a19

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