- 1). Make a solution of the chelating agent in water. Most chelating agents will dissolve in water without problem. Tap, distilled and de-ionized water have a pH that lies between 5 and 7.5. Dissolve approximately 0.01 moles of the chelating agent in 100 ml of distilled water.
- 2). Add a few drops of a metal nitrate solution to the beaker containing the chelating agent. The chelating agent will bind with the metal ion and displace the previously bound ions. For example, use CuNO3 as the metal nitrate. The blue color of copper nitrate disappears as the chelating agent binds with the copper in solution. The chelating agent displaces the nitrate ions in the complex.
- 3). Add 1 M HCl to the beaker until the pH of the solution drops below the effective range of the chelating agent. Continuing the example from above, upon the addition of enough acid to drop the pH range below the effective range of the chelating agent, the blue color returns. The acid disrupts the chelating effect once the pH of the solution drops below the chelating agent's effective pH range. When this happens, the chelating agent will release the copper ions and the solution will exhibit the characteristic blue color of copper nitrate.
- 4). Add 1 M NaOH to the beaker one drop at a time until the pH of the solution shifts to the other end of the pH range that the chelating agent works at. As the pH increases beyond the working range of the chelating agent, the metal ion is released from the chelating agent and is available to bind with other ions. Continuing the example, the copper binds with the OH- ions and forms copper hydroxide. Copper hydroxide is a solid and will drop out of solution and collect on the bottom of the beaker.
SHARE
