| 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.
