The rate of mass transfer of metal chlorides between hydrochloric acid and alkylammonium chloride solutions

A kinetic study of the transfer of niobium(V) from 10.8 M hydrochloric acid solution into chloroform solutions of bis (3,5,5-trimethylhexyl)ammonium chloride using the single-drop technique is reported. A study by vapor phase osmometry of the dimerization of the amine hydrochloride salt in chloroform solution is also reported. The interfacial reaction for niobium(V) transfer can be described by the equation NbCl6- + BTHA.HClsub(i) = BTHA.H(NbCl6)sub(i) + Cl- where the logarithms of the rate constants of the forward and reverse reactions are -4.40 +- 0.10 and -5.56 +- 0.05, respectively. Amine hydrochloride monomer is rapidly supplied to the interface by dissociation of the dominant dimeric species, where it reacts with a singly-charged anion which is formally described as NbCl6-. (author)