[The polarimetric determination of pentavalent vanadium by using quinine chlorohydrate as reagent].

The researches of the authors on the quinine chlorohydrate QH+Cl- and sodium metavanadate (Vv) reaction have led to the elaboration of two methods--a conductometric one and a gravimetric one--of dozing the QH+Cl- and, in general, of any quinine soluble salt with NaVO3. The methods, that have applications in the domain of drugs and is based on the formation of a white precipitate, in which the molar ratio QH+:Vv = 1:1. Since some authors have used quinine as a reagent in order to determine polarimetrically some ions (Ag+ and Cu2+), by taking into consideration the optic activity of quinine, we have aimed at using the formation reaction of QHVO3 for quantitatively determine the Vv with quinine chlorohydrate, by measuring the rotation angle of polarized light alpha both for the excess of QHCl reagent and for the solution obtained by dissolving the QHVO3 precipitate formed within the reaction. For this purpose there has been necessary the construction of two standard scales alpha = f(c) and there has been suggested a working methodology for the dozing of Vv with quinine chlorohydrate or any other of its soluble salts, by using any laboratory polarimeter. The results are satisfactory and depend on the sensitivity of the apparatus.