Spectrophotometric Investigation of Cobalt Chloride Complex Formation in Aqueous Calcium Nitrate–Ammonium Nitrate Melts at T = 328.15 K: Influence of Water Content

• Published in: Journal of solution chemistry 2019-10, Vol.48 (10), p.1364-1377
• Main Authors: Vraneš, Milan B., Papović, Snežana M., Gadžurić, Slobodan B.
• Format: Article
• Language: English
• Subjects: Absorption spectra; Ammonium nitrate; Blue shift; Calcium nitrate; Chemistry; Chemistry and Materials Science; Chlorides; Complex formation; Condensed Matter Physics; Geochemistry; Industrial Chemistry/Chemical Engineering; Inorganic Chemistry; Mathematical analysis; Moisture content; Nitrates; Oceanography; Physical Chemistry; Spectrophotometry; Stability constants; Water chemistry
• ISSN: 0095-9782; 1572-8927
• DOI: 10.1007/s10953-019-00920-z

In this work, the absorption spectra of cobalt(II) nitrate and chloride complexes in the composition x Ca(NO 3 ) 2 –(1 –  x )NH 4 NO 3 –H 2 O 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 0.3 Ca(NO 3 ) 2 –0.7 NH 4 NO 3 –H 2 O solutions with variable water content ( R  = H 2 O/salt mole ratio; R ws  = 1.0, 1.2, 1.6 and 2.0), and in x Ca(NO 3 ) 2 –(1 –  x )NH 4 NO 3 –H 2 O ( x  = 0.3, 0.5 and 0.7) solutions where the H 2 O/salt mole ratio was kept constant ( R ws  = 2.0). The blue shift of the absorption maximum with increasing water content ( R ws ) suggests simultaneous coordination by water molecules and nitrate ions. From an analysis of the spectra, it can be concluded that the following complexes: [Co(NO 3 ) 4 (H 2 O) 2 ] 2− , [Co(NO 3 ) 2 Cl 2 ] 2− and [CoCl 4 ] 2− were formed. The overall stability constants of these complexes and the corresponding resolved species spectra were calculated at T  = 328.15 K.