A quartz oscillator, operated with one of its faces in contact with a liquid, can be used as a highly sensitive microbalance. When used together with an electronic driver circuit, frequency changes will not only reflect changes of vibrating rigid mass but also detect changes of the surface microstructure. Using impedance spectroscopy we have analyzed the influence of the surface microstructure on the frequency changes. A liquid that is rigidly coupled to the surface by inclusion into voids or narrow channels can be discerned from a liquid that is viscously coupled to the surface. This analysis is shown for silver surfaces, roughened by several oxidation and reduction cycles, in chloride ion containing solutions.

We use a vector analyzer to investigate the impedance of a quartz oscillator, one face of which is exposed to a liquid. An aqueous LiCl – solution can be used to vary density and viscosity of the liquid over a wide range. The solution acts as an additional impedance with as well a real as an imaginary part. Furthermore, different electrical driver circuits have been used to excite the crystal vibrations. In most cases, our experimental results deviate from the predicted dependence of the crystal frequency from density and viscosity. These deviations are different for different driving circuits, but they do not change with the properties of the liquid.

A transistorized Pierce‐Miller‐oscillator is described which can be used to excite a quartz vibrator in contact with a solution. Changes of the resonance frequency of the quartz induced by deposition or dissolution of substances on one of its surfaces can be measured. We also describe a simple teflon holder which allows fixation of the crystal in a position in which only one of its faces is in contact with the solution.—The influence of simultaneous gas evolution on the performance of the balance is discussed. Preliminary results on the role of hydrides during nickel deposition and dissolution are presented and compared with literature data.

The anodic oxidation of ordered Cu/Au alloys was studied by quartz crystal microbalance measurements and quartz crystal impedance spectroscopy. A fast impedance measurement technique is presented, which allows us to monitor the surface microstructure during the selective dissolution. We learn that the state of the alloy surface characterized by impedance measurements after the oxidation is not necessarily equal to that during the oxidation.

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