He potassium biphthalate is a chemical compound, solid, white, soluble, which is commercially in a high purity 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 of the phthalic acid molecule is replaced by a potassium atom.
Potassium biphthalate receives this name because in its molecule there is a slightly acidic hydrogen. This hydrogen is the one that is in the -OH group that is right next to the carbonyl group, which is part of the carboxyl that does not react. This type of salt is known by the name of acid salts, because they are not totally neutral.
Index
- 1 Chemical structure
- 2 Formula
- 3 Nomenclature
- 4 Properties
- 4.1 Density
- 4.2 Molar mass
- 4.3 Solubility
- 4.4 Melting point
- 4.5 Appearance
- 4.6 Specific weight
- 5 Derivatigraphic study of potassium biftalate
- 6 Uses and applications
- 6.1 Standardization of a base (alkali = NaOH)
- 6.2 As a buffer in the determination of pH
- 7 Risks
- 7.1 Regarding health
- 7.2 Emergency and first aid
- 7.3 Personal protection measures
- 8 References
Chemical structure
Formula
C 6 H 4 COOHCOOK = C 8 H 5 KO 4
Nomenclature
- Potassium biftalate.
- Potassium acid phthalate.
- Potassium hydrogenophthalate.
Properties
Density
1.636g / mL.
Molar mass
204.22 g / mol.
Solubility
Water and alcohol
Melting point
295 ° C with decomposition.
Appearance
Solid crystalline to white.
Specific weight
1.64 gr / cm3.
Derivatigraphic study of potassium biftalate
Derivatological measurements have shown that the decomposition of potassium biphthalate starts at 190 ° C to 200 ° C, and the non-hygroscopic preparation can be prepared between 100 ° C and 150 ° C.
The decomposition proceeds in three steps, whose speed depends on the rate of temperature increase: dipotassium phthalate is formed first, phthalic anhydride and water are eliminated.
Enthalpy changes can also be obtained from the derivatogram, this produces information on the additional mechanism of thermal decomposition and changes in the state of the sample.
Uses and applications
This compound is used in analytical chemistry in titration or acid-base titration as the primary standard for standardization in the preparation of solutions of different compounds.
Standardization of a base (alkali = NaOH)
When preparing a NaOH solution, it can not be guaranteed that the concentration with which the solution remains is correct; This is due to the fact that NaOH is a very hygroscopic solid substance (it absorbs water from the air), and when weighing it it remains with some humidity, which makes the amount of substance not the most optimal.
Once the solution is prepared it is necessary to know exactly what concentration is left.
To do this, a solution is prepared with the potassium acid phthalate, which is a primary standard (due to its high stability); a few drops of acid-base phenolphthalein 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 NaOH concentration.
The following illustration illustrates the chemical reaction between potassium acid phthalate and sodium hydroxide.
As a buffer in the determination of pH
A buffer solution or buffer is formed by both the acid and the salt of the acid, this keeps it 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, it is possible that fire will 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 potentially 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 oxides of carbon that are toxic.
Regarding health
- By accidental ingestion, it can cause vomiting, diarrhea and irritation in the membranes due to its acidity.
- On inhalation causes irritation in the respiratory tract and cough.
- In the skin causes irritation.
- 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
- Wash your eyes with plenty of water, remove contact lenses if you wear them and let the water run through your eyes without being touched with your hands.
- If there was contact with the skin, remove clothing and shoes, wash with plenty of water and wash the clothes very well before using again.
- In case of ingestion, avoid causing vomiting, drink water.
- 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 the event of leakage or spillage, collect the product in a clean container and try to ensure that the powder does not disperse.
Personal protection measures
- Stay out of the place where beverages, food and feed are stored (pet food).
- Wear dust masks, neoprene gloves or PVC. Currently, nitrile gloves are used.
- Wear appropriate clothing that covers most of the body, including boots or covered shoes and safety glasses.
- Local exhaust ventilation is recommended, with a system of air extractors, taking into account the predominant wind direction.
- The product is miscible in water, it is not absorbed in the soil, it is not bioaccumulable or biodegradable, it is not expected to affect aquatic life. However, when disposing of it, it must be done with the help of specialized personnel: do not dispose of it through drains.
- Store in orange / green area, dry and ventilated cool place, and separated from incompatible material.
References
- Merck, (s.f), merckmillipore.com
- Chang R., (1992), Chemistry, (fourth edition), Mexico, McGraw-Hill Interamericana de México S.A, de C.V
- Reagents chemistry meyer, (s.f), safety data sheet, potassium biphthalate, Recuperado de, reactivosmeyer.com.mx
- Belcher, R., Erdey, L., Paulik, F., Liptay.G., (July 1960), Dermo-graphical study of potassium hydrogen phthalate, Sciencedirect , Volume 5, Issue 1 , Pages 53-57, org / 10.1016 / 0039-9140 (60) 80205-6