Concentration dependent refractive index of a binary mixture at high pressure

In the present work binary mixtures of varying concentrations of two miscible hydrocarbons, 1,2,3,4-tetrahydronaphtalene (THN) and n-dodecane (C12), are subjected to increasing pressure up to 50 MPa in order to investigate the dependence of the so-called concentration contrast factor (CF), i.e., (?n/?c)(p, T), on pressure level. The refractive index is measured by means of a Mach-Zehnder interferometer. The setup and experimental procedure are validated with different pure fluids in the same pressure range. The refractive index of the THN-C12 mixture is found to vary both over pressure and concentration, and the concentration CF is found to exponentially decrease as the pressure is increased. The measured values of the refractive index and the concentration CFs are compared with values obtained by two different theoretical predictions, the well-known Lorentz-Lorenz formula and an alternative one proposed by Looyenga. While the measured refractive indices agree very well with predictions given by Looyenga, the measured concentration CFs show deviations from the latter of the order of 6% and more than the double from the Lorentz-Lorenz predictions.     

Ammonium and Phosphate Quantification in Wastewater by Using a Voltammetric Electronic Tongue

Ammonia (NH₄? N) and orthophosphate (PO₄? P) quantification in wastewater treatment plants is important due to their implication in the eutrophication process. A voltammetric electronic tongue as a tool for the prediction of ammonia and orthophosphate concentrations from influent and effluent wastewater is proposed herein. An electrochemical study of the response of the ammonium and orthophosphate ions was performed in order to design a suitable waveform for each electrode. Partial Least Squares analysis was used to obtain a correlation between the data from the tongue and the concentrations of ammonia and orthophosphate measured in the laboratory showing good predictive power.     

Topical Issue on Thermal Non-Equilibrium Phenomena in Soft Matter

The European Physical Journal E - The transmission and the reflection of a shock wave by one or several impurities in viscoelastic bead chains is studied in the present paper. There is only one...