why glacial acetic acid is used_

Purification and Finalization

One of the remarkable aspects of glacial acetic acid is its ability to form hydrogen bonds between its molecules. This hydrogen bonding is primarily responsible for the relatively high freezing point in comparison to other simple carboxylic acids. For instance, acetic acid in its diluted form has a lower freezing point. When discussing this compound, one must differentiate between its concentrated (glacial) form and its diluted versions that are often encountered in various applications.

In addition to its buffering capacity, glacial acetic acid plays a role in the ionic strength of the TAE buffer. It helps to set the right environment for the separation of nucleic acids based on their size. During electrophoresis, the negatively charged DNA molecules migrate toward the positive electrode. The buffer's composition affects how efficiently these molecules can move through the gel; too little ionic strength can lead to diffuse bands, while too much can cause smearing. Glacial acetic acid helps to balance these properties, facilitating clearer and more distinct bands during gel visualization.

The cryoscopic constant \( K_f \) is defined as the change in the freezing point of a solvent caused by the presence of one mole of a non-volatile solute per kilogram of solvent. In the case of glacial acetic acid, \( K_f \) is approximately 3.9 °C kg/mol. This means that when a solute is added to glacial acetic acid, the freezing point of the solution will decrease by roughly 3.9 degrees Celsius for every mole of solute added per kilogram of glacial acetic acid.