Vibrational Spectra of Molten Salts. II. Infrared Spectra of Some Divalent Metal Nitrates in Alkalihyphen;Metal Nitrate Solutions

摘要

Infrared spectra of thin films of Mg(NO3)2, Sr(NO3)2, Ba(NO3)2, Cd(NO3)2, and Pb(NO3)2, in molten KNO3and equimolar KNO3sngbnd;NaNO3mixtures have been obtained over the spectral region 4000ndash;200 cmminus;1. All the nitrates except those of Mg and Cd were in the anhydrous state. Even at temperatures of 300deg;C or more, the magnesium and cadmium nitrate melts retained small amounts of water. As the concentrations of the divalent metal nitrates were increased, some nitrate bands split, and new lowhyphen;frequency lines were observed in some cases. These are located at 380 and 340 cmminus;1for Mg(NO3)2solutions, at 520 cmminus;1for Cd(NO3)2, and around 420 cmminus;1for Pb(NO3)2. The splitting of the ngr;3line of free nitrate decreases in the order Mg2+Cd2+Ca2+Pb2+Sr2+Ba2+. Except for Sr2+, this is the order of the ionic potentials. The observed bands are assigned and discussed in terms of complexes formed between metal and nitrate ions. Relative strengths of nitrate and chloride binding by Cd2+and Mg2+ions have been investigated by addition of Clminus;ion to the mixed nitrate systems.