| HIRANUMA APPLICATION DATA | Automatic Titrator | Data No. | J8 | Apr. 5,2019 |
| Inorganic acids & Mixed acids | Determination of boric acid in plating solution |
1. Abstract
Boric acid in plating solution is determined by neutralization titration. Boric acid cannot be directly determined by neutralization titration because it is too weak acid.
This report introduces an example of the procedure that D(-)-mannitol (mannite) is added to sample solution to generate stoicheiometric organic acid, and then it is titrated with sodium hydroxide standard solution.
| H₃BO₃ + C₆H₁₄O₆ → (C₆H₁₂O₆BO)H + 2H₂O | ・・・(1) |
| (C₆H₁₂O₆BO)H + NaOH → (C₆H₁₂O₆BO)Na + 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-501B…Fixed sleeve type ・Glass reference combination electrode GR-511B…Movable sleeve type |
|
| (2) | Reagents | ||
| Titrant | : | 0.1 mol/L Sodium hydroxide standard solution | |
| Additive solution | : | 10 mL of 20 % mannite solution | |
3. Measurement procedure
| (1) | Dispense 1 mL of sample into a 100 mL beaker with volumetric pipette. |
| (2) | Add 50 mL of DI water. |
| (3) | Add 10 mL of 20 % mannite solution. |
| (4) | Immerse electrodes and start titration with 0.1 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 | mL |
| Max Vol. | 20 | mL |
| Constant No. | 1 | |
| Size | 1 | mL |
| Blank | 0 | mL |
| Molarity | 0.1 | mol/L |
| Factor | 1.001 | |
| K | 61.83 | |
| L | 0 | |
| Unit | g/L | |
| Formula | ||
| (D-B)*K*F*M/S | ||
| Decimal Places | 4 | |
|
Auto In Pram.
|
None | |
| Mode No. | 5 | |
| Pre Int | 0 | sec |
| Del K | 5 | |
| Del Sens | 0 | mV |
| Int Time | 3 | sec |
| Int Sens | 3 | mV |
| Brt Speed | 2 | |
| Pulse | 40 | |
Measurement results
| Number of measurement |
Size (mL) |
Titrant Volume(mL) |
Boric acid Concentration (g/L) |
|---|---|---|---|
| 1 | 1 | 5.419 | 33.539 |
| 2 | 1 | 5.463 | 33.812 |
| 3 | 1 | 5.420 | 33.545 |
| Statistic calculation |
Avg. | 33.6 g/L | |
| SD | 0.155 g/L | ||
| RSD | 0.46 % | ||
Examples of titration curves
5. Note
・Interference substance on measurement
1) Samples containing some acids
After it is titrated to the endpoint pH, add mannitol solution and start titration when the sample contains some acids.
2) Samples containing some metallic salts
This method is sometimes inapplicable for the sample containing some metallic salts like iron which react with sodium hydroxide and generate precipitates.
Keywords： Boric acid, D(-)-mannitol, Neutralization titration
*Some measurement would not be possible depending on optional configuration of system.
