Mathematical model of precipitation of barium and strontium nitrates from nitric acid solutions and their mutual effect

A mathematical model describing the solubility of barium, strontium, and lead nitrates in nitric acid solutions containing 0 to 14 M HNO 3 in the temperature range from 0 to 90°С with the error no larger than 7% was developed. The model is based on the reactions of metal precipitation in the form of Me(NO 3 ) 2 at HNO 3 concentrations of up to 7–8 M and Ме(NO 3 ) 2 ·2HNO 3 at higher nitric acid concentrations, and also on the assumed formation of soluble metal nitrate complexes MeNO 3 + . A sharp increase in the barium solubility at HNO 3 concentrations lower than 0.5 M and temperatures of 50 and 90°С was interpreted assuming the possible formation of dimeric oxocations Ba 2 O 2 + or associates Ba 2 (OH) 2 2+ . A model describing the solubility of barium nitrate in the presence of strontium nitrate in HNO 3 solutions at HNO 3 concentrations in the range from 0 to 5 M was also suggested.