Dreiphasendampftensiometrie (Salzbullioskopie IV): Neue Apparatur und Anwendung

Abstract

A new apparatus for measuring the steady-state temperatur difference between two saturated solutions of the inert salt, one of them contining a foreign substance, is discribed. The three phases are, the vapour of the solvent, a saturated solution of a supporting (inert) salts, and the solid phase of the inert salt. The mixtures are kept on the top of temperature sensors and are first separated off from each other and the common atmosphere of the measuring cell using a specially formed lid. After balancing of the Wheatstone bridge, the lid is lifted and the establishing of the temperature difference is recorded using the increasing bridge potential difference ?U, which is proportional to the total concentration of all foreign species. All dissolved ions and molecules are to be considered as foreign species expect the ions of the inert salts. Three Phase Vapour Tensiometry (TPVT) was successfully used to detect binuclear species formed in the titration of diaqua-Cr(III) complexes with ethyltrimethylammonium hydroxide in saturated solution of ethyltrimethylammonium perchlorate. TPVT titrations of lanthanum nitrate with water in acetone saturated with lithium nitrate and tetraheptylammonium nitrate, respectively, gave a hydration number of 9 for La(III).