HIRANUMA APPLICATION DATA

Detergents・Bath additives・
Cosmetics

Data No.

Automatic Titrator

C6Apr. 5,
2019

Quantitative determination of sodium sulfate
in bath additive

1. Abstract
The precipitation titration using lead ion-selective electrode achieves the measurement of sulfate ions.
Lead sulfate is generated by adding lead nitrate to sulfate ion. The potential reading with lead ion -selective
electrode differs depending on the concentration of sulfate ion in sample solution. The maximum change in
potential is observed when it reaches the equivalent point of sulfate and lead ions. The concentration of sulfate
ion is determined by the titrant volume consumed until it reaches the inflection point.

SO42-＋Pb(NO3)2→PbSO4＋2NO3-

This report introduces an example of the measurement for sulfate ion in bath additive with using leadion-selective electrode.

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

Hiranuma Automatic Titrator COM series

Electrodes：

Lead ion-selective electrodePbi-081

Glass-reference combination electrodeGE-501BZ(2) Reagents
Titrant：

0.01 mol/L lead nitrate standard solution
Dissolve 1.6560 g of lead (II) nitrate in DI water and prepare
500 mL solution.

Standardization solution ：Solvent：

0.01 mol/L sulfuric acid standard solution
50 mL of diluted methanol
Mix methanol and DI water with 4:1 volume ratio.

Additive solution：

Diluted nitric acid (10 % [v/v])

3. Measurement procedure 。
(1) Standardization of 0.01 mol/L lead nitrate standard solution.
i) Dispense 10 mL of 0.01 mol/L sulfuric acid standard solution into a 100 mL beaker with volumetricpipette.
ii) Add 50 mL of solvent and stirring bar to the beaker.
iii) Immerse the electrodes into sample solution and titrate with 0.01 mol/L lead nitrate standard solution.

(2) Measurement of sodium sulfate in bath additivei) Accurately weigh about 0.4 g of bath additive with 0.1 mg digit. Dissolve it with DI water and prepare
200 mL solution using volumetric flask.
ii) Dispense 5 mL of the above solution into a 100 mL beaker with a volumetric pipette.

This aliquot of sample solution contains about 0.01 g of sample (0.4 g × 5 mL/200 mL).
iii) Add 50 mL of solvent and a stirring bar to the beaker.
vi) Immerse the electrodes into sample solution and add a few drops of diluted nitric acid by a dropperwith reading the pH using GR-501B to adjust the pH to about 4. Start titration with 0.01 mol/L leadnitrate standard solution.

4. Measurement conditions and results
Examples of titration conditions(1) Standardization of 0.01 mol/L lead nitrate standard solution.
Cnd. No.
MethodBuret No.
Amp No.
D.UnitS- Timer
C.P. mL
T.Timer
D.P. mLEnd Sens
Over mLMax Vol.

1Auto12mV
08100500.320secmL
sec
mL
mL
mL

Constant No.
SizeBlank
Morality
FactorKL
Unit
Formula110 mL0 mL
0.01 mol/L
0.997
00Fact1

S/(D-B)*F
Decimal Places
3Auto input parameter

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

805053240

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

805053240sec
mV
sec
mV

None

(2) Titration of sodium sulfate with lead nitrate
Cnd. No.
MethodBuret No.
Amp No.
D.UnitS- Timer
C.P. mLT.Timer
D.P. mLEnd Sens
Over mLMax Vol.

1
Auto12mV
000050
0.3
20

secmL
sec
mL
mL
mL

Constant No.
1Size
0.01
Blank
0Morality
0.01
Factor
0.9849K142.04
L0Unit%Formula(D-B)*K*F*M/(S*10)
Decimal Places
3
Auto input parameter

ｇmL
mol/L

None

sec
mV
sec
mV

Measurement results(1) Standardization of 0.01 mol/L lead nitrate standard solution

Number ofSize

Titrant

Measurement(mL)

Volume (mL)

1210Factor

10.1180.985410.1290.98430.9849Average(2) Titration of sodium sulfate with lead nitrate

Number ofActual Sample

Titrant

Concentration

Measurement

Size (g)Volume (mL)

(%)

1

5.826

81.5032

5.832

81.587

5.867

82.0774

5.841

81.713

5

5.834

81.615

3

Statistic
calculation

0.0100

Average81.70 %

Standard deviation

0.22 %

Coefficient of variation

0.27 %

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

5. Note(1) The reading of the potential might decrease with repeated use of the lead ion-selective electrode. Polishing thesurface of the lead ion-selective electrode with a fine sandpaper (P800 or finer) improves the condition of theelectrode.
(2) The response sensitivity of the lead ion-selective electrode might decrease because of the influence ofcoexisting materials and the measurement would be failed. There is a possibility that this method cannot beapplied for a sample containing multiple components like plating solution.
(3) The total amount of sodium sulfate and magnesium sulfate are detected when the sample contains bothsubstances. The magnesium ion of magnesium sulfate can be determined by photometric titration. The
concentration of sodium sulfate can be calculated by subtracting the concentration of magnesium sulfate fromthe result of total amount.
Keywords：Sulfate ion, Precipitation titration, Lead ion-selective electrode, Bath additive*Some measurement would not be possible depending on optional configuration of system.