Fractional determination of nitric acid and acetic acid | Autotitrator COM-A19 - JM Science
HIRANUMA APPLICATION DATA Automatic Titrator Data No. J6 Apr. 5,2019
Inorganic acids & Mixed acids Fractional determination of nitric acid and acetic acid

1. Abstract

The mixed solution of nitric acid (inorganic acid) and acetic acid (organic acid) works as strong acid, and also has the strong oxidizability and solvency. It is used as the surface treatment solution for metals, glass products, and semiconductors.

This report introduces an example of the fractional and successive determination for nitric acid and acetic acid by neutralization titration with sodium hydroxide standard solution.

HNO₃ + NaOH → NaNO₃ + H₂O  ・・・(1)
CH₃COOH + NaOH → CH₃COONa + H₂O  ・・・(2)

2. Configuration of instruments and Reagents

(1) Configuration of instruments
  Main unit : Hiranuma Automatic Titrator COM series
  Electrodes : Glass electrode GE-101B
Reference electrode RE-201Z
*Instead of the above electrodes, the following electrodes are usable.
・Glass reference combination electrode GR-501BZ…Fixed sleeve type
・Glass reference combination electrode GR-511BZ…Moveable sleeve type
(2) Reagents    
  Titrant : 1 mol/L Sodium hydroxide standard solution

3. Measurement procedure

(1) Dispense 1 mL of sample into a 100 mL beaker with a volumetric pipette.
(2) Add 40 mL of CO₂-free DI water.
(3) Immerse electrodes and start titration with 1 mol/L sodium hydroxide standard solution.

4. Measurement conditions and results

Examples of titration conditions

(1) Titration condition for nitric acid

 

 

Cndt No 1
Method Auto
Buret No. 1
Amp No. 1
D. Unit pH
S-Timer 10 sec
C.P. mL 0 mL
T Timer 0 sec
D.P. mL 0 mL
End Sens 150
Over mL 0 mL
Max Vol. 20 mL
Constant No. 1
Size 1 mL
Blank 0 mL
Molarity 1 mol/L
Factor 1.005
K 63.01
L 0
Unit g/L
Formula (D-M)*K*F*M/S
Decimal Places 3
Auto In Pram.
None
Mode No. 4
Pre Int 0 sec
Del K 9
Del Sens 0 mV
Int Time 3 sec
Int Sens 3 mV
Brt Speed 2
Pulse 40

 

(2) Titration condition for acetic acid

 

 

Cndt No 2
Method Auto
Buret No. 1
Amp No. 1
D. Unit pH
S-Timer 0 sec
C.P. mL 0 mL
T Timer 0 sec
D.P. mL 0 mL
End Sens 1000
Over mL 0.2 mL
Max Vol. 20 mL
Constant No. 2
Size 1 mL
Blank 0 mL
Molarity 1 mol/L
Factor 1.005
K 60.05
L 0
Unit g/L
Formula (D-M)*K*F*M/S
Decimal Places 3
Auto In Pram.
None
Mode No. 4
Pre Int 0 sec
Del K 9
Del Sens 0 mV
Int Time 3 sec
Int Sens 3 mV
Brt Speed 2
Pulse 40

 

*Connect the condition (1) and (2) for successive titration.

Measurement results

Number of
measurement
Size
(mL)
Titrant volume at
1st endpoint (mL)
Nitric acid
(g/L)
Titrant volume at
2nd endpoint (mL)
Acetic acid
(g/L)
1 1 4.708 289.134 8.314 501.752
2 1 4.709 298.198 8.311 501.571
3 1 4.710 298.261 8.318 501.993
Statistic
calculation
Avg. 295.2 g/L Avg. 501.8 g/L
SD 5.25 g/L SD 0.21 g/L
RSD 1.78 % RSD 0.04 %

Examples of titration curves

5. Note

・Control of titrant
The concentrated sodium hydroxide standard solution is used as titrant in this report. The carbon dioxide gas absorber (soda lime) on reagent bottle has to be regularly exchanged because sodium hydroxide readily absorbs carbon dioxide gas in the air (formula (3)). The titrant contains sodium carbonate if it absorbed carbon dioxide gas. When using this titrant, the titration curve would show the inflection points at pH around 4 and 9 (formula (4) and (5)).

2NaOH + CO₂ → Na₂CO₃ + H₂O  ・・・(3)
Na₂CO₃ + HNO₃ → NaHCO₃ + NaNO₃  ・・・(4)
NaHCO₃ + HNO₃ → NaNO₃ + CO₂ + H₂O  ・・・(5)

 

Keywords: Nitric acid, Acetic acid, Neutralization titration, Fractional titration, Successive titration

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

Hiranuma aquacounter autotitrator com-a19Inorganic acids & mixed acids

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