Karl Fischer & Potentiometric Titration Application Library

Simultaneous determination of acetic acid and ammonium acetate using automated titration. Improve process control in semiconductor and industrial applications.

Oxalic acid has two carboxy groups (-COOH) in the molecule , it is called dicarboxylic acid. There are two crystallization water molecules in the molecule. Oxalic acid is ortho acid and forms the following structure. It is readily oxidized by the acid stronger than formic acid.

Oxalic acid is used as raw material of organic compound. In addition, sodium salt of oxalic acid is used as standard substance of quantitative analysis because it quantitatively reacts with oxidizing agent like potassium permanganate and is stably conservable. The determination method for oxalic acid is prescribed in JIS K8519, it is determined by potassium permanganate standard solution. This report introduces an example of the purity determination for oxalic acid using redox titration as described below (formula 1) and neutralization titration with sodium hydroxide titrant (formula 2).

Measure lactic acid in food products to monitor fermentation, spoilage, and quality. Improve consistency and shelf life control with automated titration.

Determine citric acid purity for food additive quality control. Ensure consistent formulation, regulatory compliance, and product performance with automated titration.

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.

The mixed solution of nitric acid and phosphoric acid works as strong acid, and also 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 phosphoric acid by neutralization titration with sodium hydroxide standard solution. When nitric acid and phosphoric acid are titrated by neutralization titration using a glass electrode for pH measurement, two inflection points appear on the titration curve. The first inflection point appears as the total amount of nitric acid and phosphoric acid (reaction formula (1) and (2)). Sodium dihydrogen phosphate, which is the product of reaction equation (2), subsequently reacts with sodium hydroxide and shows an inflection point in the second stage (reaction equation (3)). Therefore, it is possible to obtain the phosphoric acid concentration from the second inflection point, and nitric acid concentration could be obtained with subtracting titration volume at the second inflection point from the first inflection point.

Boric acid is a critical buffer in nickel plating baths. Learn how automated potentiometric titration with mannitol improves accuracy, repeatability, and process control.

The mixed solution of nitric acid (inorganic acid) and acetic acid (organic acid) works as strong acid, and also has the strong oxidizable properties 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 + NaOH → NaNO₃ + H₂O・・・(1)
CH₃COOH + NaOH → CH₃COONa + H₂O・・・(2)

Phosphoric acid is important reagent as a raw material of chemical industrial reagents and fertilizers. Its production amount is large and it is used in a broad range of fields. The determination method of phosphoric acid purity is described in “JIS (Japanese Industrial Standards) K9005:2006 Phosphoric acid (reagent)”; the purity of phosphoric acid is determined by potentiometric titration with sodium hydroxide standard solution. This report introduces an example of the purity determination of phosphoric acid by this method.

Phosphoric acid reacts with sodium hydroxide as described in the reaction formula (1) ~ (3) because phosphoric acid is triacid. The titration curve of neutralization titration for phosphoric acid theoretically has three inflection points, but practically it shows two inflection points. This is because third acid dissociation constant (pKa) of phosphoric acid is 12.35, the pH at the third inflection point is undetectable value by the titration with strongly basic titrant. The purity of phosphoric acid is determined by the titration to the second inflection point in this measurement.
H₃PO₄ + NaOH → NaH₂PO₄ + H₂O・・・(1)
NaH₂PO₄ + NaOH → Na₂HPO₄ + H₂O・・・(2)
Na₂HPO₄ + NaOH → Na₃HPO₄ + H₂O・・(3)

Sulfuric acid is one of the most elemental reagent in chemical industrial reagents. Its production amount is large and it is used in a broad range of fields. Since sulfuric acid absorbs moisture in atmosphere because of its properties, the purity of sulfuric acid is gradually reduced. “JIS (Japanese Industrial Standards) K8951: 2006 Sulfuric acid (Reagent)” describes the determination method for purity of sulfuric acid which it is titrated with sodium hydroxide standard solution until the color of bromothymol blue indicator changes from yellow to blue green at the endpoint. However, this report introduces an example of the potentiometric titration with sodium hydroxide for the measurement of the accurately-weighed sample.

The neutralization titration for sulfuric acid with sodium hydroxide proceeds as two step reaction because sulfuric acid is diacid. However, the first and second dissociation of sulfuric acid cannot be discriminated due to the leveling effect of water. Therefore the single inflection point is observed on the titration curve and the reaction formula on this measurement can be described as below.
H₂SO₄ + 2NaOH → Na₂SO₄ + H₂O・・・(1)

Sodium hypochlorite is produced by having sodium hydroxide absorb chlorine gas. Produced sodium hypochlorite contains residual alkali (sodium hydroxide, sodium carbonate) and sodium chloride generated by the degradation of hypochlorous acid. The residual alkali is determined by neutralization titration, and sodium chloride is determined by precipitation titration.

This report introduces an example of the determination for sodium chloride in the sodium hypochlorite with potentiometric titration.