SPECTROPHOTOMETRIC INVESTIGATION OF COBALT BROMIDE COMPLEX FORMATION IN AQUEOUS CALCIUM NITRATE– AMMONIUM NITRATE MELTS AT T = 328.15 K. INFLUENCE OF WATER CONTENT

In this work, the absorption spectra of cobalt(II) nitrate and bromide complexes in the composition 0.3Ca(NO3)2 – 0.7NH4NO3 – H2O have been investigated in the 400-800 nm range of wavelength at T = 328.15 K and atmospheric pressure P = 101.3 kPa. Spectra were recorded in solutions with variable water content (R = H2O/salt mole ratio; R = 1.0, 1.2 and 1.6). The blue shift of the absorption maximum with the water content increase (R) suggest simultaneous coordination by water molecules and nitrate ions. From an analysis of the spectra, it can be concluded that the following: [Co(NO3)4(H2O)2]2−, [Co(NO3)2Br2]2− and [CoBr4]2− complexes were formed. The overall stability constants of these complexes species spectra were calculated at T = 328.15 K.