Several methods have been suggested for preparing pure, anhydrous acetonitrile for electrochemical purposes 1. All are satisfactory, but there can be a great difference between a freshly distilled solvent and the solution containing the supporting electrolyte. The transfer of the solvent into the cell, the use of a not perfectly anhydrous supporting electrolyte and in general any contact with the atmosphere and the surroundings can raise the water content of solutions to a level considerable higher than the minimum allowed. To overcome this many authors suggest the use of molecular sieves in the final dehydration of a solution 1-3
This note reports on a very simple method for carrying out the final dehydration of a solution in the working cell.
Since water undergoes an anodic oxidation on a platinum electrode in acetonitrile medium near the anodic limit of the solvent 2, we suggest its elimination by a controlled-potential electrolysis. In this procedure hydrogen ions are produced. It is however well known that the presence of H Γ· can either deeply modify the mechanism of a reaction 4-6 or change the potential values of electrochemical reactions. Moreover the determination of protons released in an anodic oxidation can help in elucidating a complex mechanism 7-s. We therefore suggest their elimination by a second controlled potential electrolysis.