Why is there a difference in the solubility of EDTA and EDTA potassium?

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EDTA and EDTA dipotassium are two widely used chelating agents that play a role in many chemical reactions, which are closely related to their performance. It is worth mentioning their solubility. The solubility of EDTA is 0.5g/L (25 ℃), and the solubility of EDTA dipotassium is ≥ 60% (g/ml, 25 ℃). From the surface, EDTA dipotassium contains EDTA, but why is there such a difference in solubility between the two? Below, we will give you a specific introduction.

1Solubility of EDTA

EDTA is a weakly acidic chelating agent that contains two hydrolyzable carboxyl groups (- COOH) in its molecules. In water, EDTA can partially dissociate into two ions: E - and D2-, producing both H+and OH - ions that form hydrates with water molecules, allowing EDTA to dissolve in water. According to relevant research, the mass fraction in EDTA aqueous solution is usually 0.1% to 0.5%, which means that 0.1 to 0.5 grams of EDTA can be dissolved in every 100 grams of solvent. If the temperature increases, the solubility of EDTA will also increase, because high temperature will increase the kinetic energy of water molecules, causing them to interact with EDTA molecules. Therefore, the standard is to dissolve at room temperature of 25 degrees Celsius.

2Solubility of EDTA dipotassium

EDTA dipotassium is composed of two potassium ions (K+) and two EDTA anions (E - or OH -). Compared to EDTA, EDTA dipotassium has a stronger alkalinity, resulting in a higher solubility. Similarly, as the temperature increases, the solubility of EDTA potassium also increases, so under the same conditions of 25 degrees Celsius, the solubility of EDTA potassium is ≥ 60%.

3Reasons for the Difference in Solubility of EDTA and EDTA Dipotassium

1. Acidity and alkalinity: EDTA molecule contains four hydrolyzable carboxyl groups, so it is a weak acid compound, while EDTA dipotassium is an alkaline compound. The ions produced by the two are different, and the Ionic strength and the action of water molecules are different, so there is a natural difference.

2. Molecular structure: another factor that leads to the difference in solubility is their molecular structure. EDTA molecules contain less carboxyl and amino groups than EDTA dipotassium molecules. EDTA dipotassium is alkaline, so its solubility is higher.

3. Coordination number: EDTA and EDTA dipotassium have different Coordination number. The former forms a complex, while EDTA dipotassium can form two different complexes, such as dihydrate, which have different stability and solubility.

Understanding the solubility of EDTA and EDTA dipotassium can help everyone better use it and optimize the conditions of chemical reactions. As a professional manufacturer of EDTA potassium, Desheng produces analytical grade products with a solubility of ≥ 60% (g/ml, 25 ℃), which is easy to operate and conducive to the completion of various experiments. If you are interested, please click on the website to inquire and purchase!