HIRANUMA APPLICATION DATA

Automatic Titrator

Data No.

K2

Jul. 14,2020

Determination of formic acid

Organic acid
1. Abstract

Formic acid is monobasic carbonic acid, which belongs to lower saturated fatty acid group. Formic acidhas a little different properties from other saturated fatty acids; it has significantly strong acidity (12 timesstronger than acetic acid) and reducing character, degrades to water and carbon dioxide gas by the oxidation. It
can also reduce ammoniacal silver nitrate.
The neutralization titration method with sodium hydroxide standard solution for the determination offormic acid is prescribed in “JIS K8264. This report introduces an example of the potentiometric titration withglass electrode instead of indicator method using phenolphthalein prescribed in JIS.
H･COOH+NaOH→

H･COONa+H2 O・・・(1)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) Reagent
Titrant:

1 mol/L Sodium hydroxide standard solution

3. Measurement procedure(1) Take 20 mL of DI water into a 100 mL beaker.
(2) Add about 1 g of sample to the beaker and weigh accurately with 0.1 mg digit.
(3) Add about 50 mL of DI water and stirring bar to the beaker and stir to homogenize it.
(4) Immerse electrodes and start titration with 1 mol/L sodium hydroxide standard solution.

4. Measurement conditions and results
Example of titration condition
Cndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. mLT Timer
D.P. mLEnd Sens
Over mL
Max.Vol.

1Auto
11pH
5000500
0.120sec
mLsec
mL
mL
mL

ConstantNo.
SizeBlank
Molarity
FactorKL
Unit
Formula11.005 g0 mL
1.000 mol/L
1.005
46.03
0%(D-B)*K*F*M/(S*10)

Decimal Places
Auto In Pram.

3Non

Mode No.
Pre Int
Del K
Del Sens
Int Time
Int Sens
Brt SpeedPulse

805053240sec
mVsec
mV

* Enter the molecular weight of formic acid (46.03) to parameter “K”.

Measurement results

Number ofSize

Titrant

Concentration

Measurement(g)

Volume (mL)(%)

11.005019.17888.27621.0025

19.07588.0213

1.003419.17588.403

Statistic
calculation

Example of titration curve

Avg.

88.23 %

SD

0.195 %

RSD

0.221 %

5. Note(1) Collection of sample
The sample is collected directly to the beaker and weighed accurately. The accuracy of sample collection
influences the measurement accuracy. Please note that the sample should be carefully taken and accuratelyweighed.
(2) 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 (2)). The standard solution of sodium hydroxide that hasabsorbed carbon dioxide contains sodium carbonate, and the inflection point on titration curve may beunclear due to buffer capacity of sodium hydrogen carbonate generated in the reaction with an acidic samp le(formula (3)).
2NaOH+CO2→

Na2CO3+HCOOH→

Na2CO3+NaHCO3H2 O・・・(2)+・・・(3)

HCOONaKeywords: Formic acid, Sodium hydroxide, Neutralization, JIS K8264*Some measurement would not be possible depending on optional configuration of system.