Composition of precipitates of barium and strontium nitrates crystallizing from nitric acid solutions

Abstract

The chemical compositions of Ba(NO3)2 и Sr(NO3)2 precipitates obtained by precipitation from HNO3 solutions of various concentrations were determined using an inert tracer. The data of chemical analysis and IR spectroscopy suggest the presence of HNO3 in the precipitates of barium and strontium nitrates and of their solid solutions, formed from concentrated nitric acid solutions. The IR spectra of 0 to 23.5 M aqueous HNO3 solutions were measured and compared to the spectra obtained by subtraction of the spectra of dry barium or strontium nitrate from the spectra of the wet crystals. The IR spectra and structure of the double salt K2Ba(NO3)4 were also examined; they were found to differ from those of the components. The results of X-ray diffraction analysis are indicative of the formation of the precipitates with the structure similar to that of the dry salts, with simultaneously occurring changes in the texture of the precipitates formed from concentrated HNO3. It was suggested that barium and strontium nitrates could form unstable adducts with HNO3.