Determination of formic acid | Autotitrator COM-A19 - JM Science
HIRANUMA APPLICATION DATA Automatic Titrator Data No. K2 Jul. 14,2020
Organic acid Determination of formic acid

1. Abstract

Formic acid is monobasic carbonic acid , which belongs to lower saturated fatty acid group. Formic acid has a little different properties from other saturated fatty acids; it has significantly strong acidity (12 times stronger 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 of formic acid is prescribed in “JIS K8264. This report introduces an example of the potentiometric titration with glass electrode instead of indicator method using phenolphthalein prescribed in JIS.


2. Configuration of instruments and Reagents

(1) Configuration of instruments
  Main unit : Hiranuma Automatic Titrator COM series
  Electrode : 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) 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

Examples of titration conditions

Cndt No 1
Method Auto
Buret No. 1
Amp No. 1
D. Unit pH
S-Timer 5 sec
C.P. mL 0 mL
T Timer 0 sec
D.P. mL 0 mL
End Sens 500
Over mL 0.1 mL
Max Vol. 20 mL
Constant No. 1
Size 1.005 g
Blank 0 mL
Molarity 1 mol/L
Factor 1.005
K 46.03
L 0
Unit %
Formula
(D-B)*K*F*M/(S*10)
Decimal Places 3
Auto input Param.
Non
Mode No. 8
Pre Int 0 sec
Del K 5
Del Sens 0 mV
Int Time 5 sec
Int Sens 3 mV
Brt Speed 2
Pulse 40

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

Measurement results

Number of
measurement
Size
(g)
Titrant
volume(mL)
Concentration (%)
1 1.0050 19.178 88.276
2 1.0025 19.075 88.021
3 1.0034 19.175 88.403
Statistic
calculation
Avg. 88.23 %
SD 0.195 %
RSD 0.221 %

 

Example of titration curve

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 accurately weighed.

(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 has absorbed carbon dioxide contains sodium carbonate, and the inflection point on titration curve may be unclear due to buffer capacity of sodium hydrogen carbonate generated in the reaction with an acidic sample (formula (3)).
Keywords: Formic acid, Sodium hydroxide, Neutralization, JIS K8264

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

Hiranuma aquacounter autotitrator com-a19Organic acid

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