THE ADSORPTION OF NICOTINIC-ACID, NICOTINAMIDE AND NIPECOTAMIDE FROM AQUEOUS-SOLUTIONS ON THE (11O) FACE OF SILVER

The adsorption of nicotinic acid, nicotinamide and nipecotamide at Ag( 110) single crystal electrode has been studied from aqueous solutions of 0.1 KF. It was found, that the adsorption of Nc is greater than tha t of NcA and NpA. It was possible, however, to determine quantitativel y the amount of the adsorption only for lower concentrations of NC, wh ere the anionic form Nc(-) dominates in the solution. At the zero char ge potential and at the positively charged surface the molecules of Nc (-) adsorb flat (the pyridine ring parallel to the electrode) similarl y as on the mercury. The standard Gibbs energy of Nc(-) adsorption at Ag is smaller than at Hg. In the case of NcA and NpA systems it was no t possible to derive quantitatively the parameters of their adsorption because of the probable coadsorption of F- ions at the Ag surface.