POTASSIUM BIPHTHALATE: STRUCTURE, NOMENCLATURE, USES AND RISKS - CHEMISTRY - 2025

The potassium biphthalate is a soluble, solid, white chemical compound that is commercially in highly pure state. It is used as a primary standard to standardize solutions in acid-base titrations; It is also used as a buffer solution to keep the pH of the solutions stable.

It is a stable, non-hygroscopic compound, which facilitates the preparation of the solution since it does not absorb water during the weighing process. It can be prepared by the reaction between phthalic acid and a KOH solution, in which a hydrogen in the phthalic acid molecule is replaced by a potassium atom.

Potassium biphthalate receives this name because there is slightly acidic hydrogen in its molecule. This hydrogen is the one found in the -OH group that is right next to the carbonyl group, which is part of the carboxyl that does not react. These types of salts are known by the name of acid salts, as they are not totally neutral.

Chemical structure

Formula

C ₆ H ₄ COOHCOOK = C ₈ H ₅ KO ₄

Nomenclature

- Potassium biphthalate.

- Potassium acid phthalate.

- Potassium hydrogenphthalate.

Properties

Density

1,636g / mL.

Molar mass

204.22 g / mol.

Solubility

Water and alcohol.

Melting point

295 ° C with decomposition.

Appearance

Crystalline to white solid.

Specific weight

1.64 gr / cm3.

Derivatographic study of potassium biphthalate

This compound is used in analytical chemistry in acid-base titration or titration as a primary standard for standardization in the preparation of solutions of different compounds.

Standardization of a base (alkali = NaOH)

When preparing a NaOH solution, it cannot be guaranteed that the concentration of the solution is correct; This is due to the fact that NaOH is a very hygroscopic solid substance (it absorbs water from the air), and when it is weighed it is left with some moisture, which makes the amount of substance not the most optimal.

Once the solution is prepared, it is necessary to know exactly what concentration it has been.

For this, a solution is prepared with potassium acid phthalate, which is a primary standard (due to its high stability); A few drops of phenolphthalein acid-base indicator are added and the NaOH solution is added as titrant until a pink color remains present in the potassium acid phthalate solution.

With the data obtained, the pertinent calculations are carried out to find the real concentration of NaOH.

The following image illustrates the chemical reaction between potassium acid phthalate and sodium hydroxide.

As a buffer in pH determination

A buffer solution or buffer is one that is formed by both the acid and the acid salt, this makes it remain under conditions such that the pH value does not change when small amounts of acid or base are added.

Risks

- Exposure to fire. As with most organic solids, fire can occur at elevated temperatures or by contact with an ignition source.

- Fine dust dispersed in air in sufficient concentrations, and in the presence of an ignition source, is a potential dangerous dust explosion.

- It is a stable substance at room temperature and under adequate storage conditions. Avoid excessive heat and humidity.

- May be incompatible with strong oxidants such as nitric acid.

- Decomposition can form carbon oxides which are toxic.

Regarding health

- By accidental ingestion, it can cause vomiting, diarrhea and irritation of the membranes due to its acidity.

- Inhalation causes respiratory tract irritation and coughing.

- Causes irritation on the skin.

- In the eyes it causes irritation, redness and pain.

- It is considered that it is not a carcinogenic, teratogenic or mutagenic substance.

Emergency and first aid

- Rinse the eyes with plenty of water, remove contact lenses if wearing them and let the water run through the eyes without being touched with the hands.

- If there was contact with the skin, remove clothing and footwear, wash with plenty of water and wash the garments very well before using again.

- In case of ingestion, avoid inducing vomiting, give water to drink.

- In case of inhalation, take the person to breathe fresh air; in case of difficult breathing, supply oxygen.

- In all cases ask for urgent medical assistance.

- In case of leakage or spillage, collect the product in a clean container and try not to scatter the powder.

Personal protection measures

- Keep out of the place where drinks, food and feed (pet food) are stored.

- Use dust masks, neoprene or PVC gloves. Nitrile gloves are used today.

- Wear suitable clothing that covers most of the body, including covered boots or shoes and safety glasses.

- Local exhaust ventilation is recommended, with an air extractor system, taking into account the prevailing wind direction.

- The product is miscible in water, it does not absorb into the soil, it is not bioaccumulative or biodegradable, it is not expected to affect aquatic life. However, when disposing of it, it should be done with the help of specialized personnel: do not dispose of via drains.

- Store in orange / green area, cool dry and ventilated place, and separated from incompatible material.

References

1. Merck, (nd), merckmillipore.com
2. Chang R., (1992), Chemistry, (fourth edition), Mexico, McGraw-Hill Interamericana de México SA, de CV
3. Reagents chemistry meyer, (nd), safety data sheet, potassium biphthalate, Recovered from, reaivosmeyer.com.mx
4. Belcher, R., Erdey, L., Paulik, F., Liptay.G., (July 1960), Derivatographic Study of Potassium Hydrogen Phthalate, Sciencedirect, Volume 5, Issue 1, Pages 53-57, org / 10.1016 / 0039 -9140 (60) 80205-6