S. Bordi

An automated apparatus for interfacial tension measurements by the sessile drop technique

A fully computer controlled apparatus for interfacial tension measurements at the mercury/solution or solution/solution interface is described. The apparatus is based on the drop‐shape technique and employs a solid state video camera to take the drop profile; measurements can be accomplished as a function of interface polarization potential, temperature and solution concentration. Overall data reproducibility is better than 0.06%, with an acquisition time of about 45 s for each experimental data point.

Surface tension measurements: toward higher accuracy

Abstract In order to implement a fully computer controlled apparatus for the measure of interfacial tension at the liquid—liquid polarized interface using a drop shape technique, we studied by computer simulation the accuracy obtainable as a function of the characteristics of the imaging device. Preliminary tests performed after assembling the apparatus confirmed the possibility to reach an absolute and differential accuracy of 0.2 and 0.05 dyne cm −1 at the Hg—aqueous solution interface.

Surface potential and non-ionic surfactants

Summary Surface potential measurements on water solutions of non-ionic polyoxyethylene surfactants were performed by the ionization method. The surface potential was sensitive to very small quantities (1×10−2 p.p.m.) of these surfactants in solution. This was also true when moderate quantities of electrolytes (CaCl2) or of ionic surfactants (sodium dodecylsulphate) were added to the solutions. The method may be utilized in the water pollution field; for instance to control the efficiency of water purification plants in industries employing non-ionic surfactants.

On the interfacial excess entropy at the mercury-aqueous solution interface

Abstract The thermodynamic interfacial excess entropy has been measured at the mercury-aqueous NACl and KCl interface as a function of charge density, temperature and concentration by means of an automated apparatus employing the sessile drop technique. Several discrepancies emerge from a comparison with previously existing data, notably in the position and value of the entropy maximum.