HIRANUMA APPLICATION DATA

Data No.

Automatic Titrator

J6Apr. 5,
2019

Fractional determination ofnitric acid and acetic acid

Inorganic acids &Mixed acids
1. Abstract

The mixed solution of nitric acid (inorganic acid) and acetic acid (organic acid) works as strong acid, andalso 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＋CH3COOH

NaOH＋→NaOH

NaNO3→＋・・・(1)H2 O

CH3COONa＋

H2 O・・・(2)2. Configuration of instruments and reagents(1) Configuration of instruments
Main unit:

Hiranuma Automatic Titrator COM series

Electrodes:

Glass electrodeGE-101B

Reference electrodeRE-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) ReagentTitrant:

1 mol/L Sodium hydroxide standard solution3. 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 acidCndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. mLT Timer
D.P. mLEnd Sens
Over mL
Max.Vol.

1Auto11pH
10000150
020

ConstantNo.
SizeBlank
Molarity
FactorKLUnitFormulasec
mLsec
mL
mL
mL

11.0000.0001.000
1.005
63.01
0.000g/L

mL
mLmol/L

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

409033240

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

409033240sec
mVsec
mV

(D-M)*K*F*M/S
3Non

Decimal Places
Auto In Pram.

(2) Titration condition for acetic acid
Cndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. mLT Timer
D.P. mLEnd Sens
Over mLMax.Vol.

2
Auto
1
1pH
00001000
0.2
20

sec
mL
sec
mL
mL
mL

ConstantNo.
SizeBlank
Molarity
FactorKL
Unit
Formula

2
1.000
0.000
1.000
1.005
60.05
0.000g/L

mL
mL
mol/L

sec
mV
sec
mV

(D-M)*K*F*M/S
3
Non

Decimal Places
Auto In Pram.

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

Measurement results
Titrant
volume at
1st endpoint
(mL)

Size

Measurement

(mL)

1

1

4.708

289.1348.314

501.7522

14.709298.1988.311

501.5713

14.710298.2618.318

501.993Avg.

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 %

Statistic calculation

Nitric acidTitrant
volume at
2nd endpoint(mL)

Number of(g/L)

Acetic acid(g/L)

Example of titration curve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 absorbedcarbon 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

Na2CO3+HNO3→NaHCO3+HNO3→

H2 O・・・(3)

NaHCO3+NaNO3・・・(4)NaNO3CO2+++H2 O・・・(5)Keywords: Nitric acid, Acetic acid, Neutralization titration, Fractional titration, Successive titration*Some measurement would not be possible depending on optional configuration of system.