Optical Investigations of Film Formation and Removal on Gold Anodes in Acidic Oxalate Solutions
RECENT investigations of the oxidation of oxalate ions in acidic solutions using gold anodes have provided electrochemical evidence for the formation of a film on this anode during steady-state electrolysis at potentials well below that for Au2O3 formation, 1.36 V normal hydrogen electrode1. The determination of the nature of the film on gold at potentials below 1.36 V using electrochemical techniques has introduced uncertainties as to whether the film is a ‘three dimensional’ oxide film or a ‘two dimensional’ chemisorbed oxygen film. Some investigators2–5 using charging curves as their basis conclude that the formation of an oxide occurs only above 1.36 V, the formation of a chemisorbed oxygen film being the process occurring below this potential. The formation of this chemisorbed oxygen film begins at potentials as low as 1 15 V (ref. 6). Other work, however, also based on electrochemical evidence, indicates that the formation of an oxide film does occur below 1.36 V (ref. 7).
Processes in solution and on the electrode surface monitored by IRS with metal film electrodes
Summary The different contributions to reflectance changes during the modulation of the potential of a film electrode in an Electro-IRS experiment, are discussed. The electrosorption and desorption of the first surface oxide layer may have a significant effect on reflectance results, even when the current required for oxide production is small compared to the faradaic currents resulting from dissolved electroactive components. The correction for surface oxide formation and for the electromodulation effect is best performed using a “blank” experiment. Linear potential changes are used for both the “blank” and the main IRS experiment; the same metal film electrode, supporting electrolyte solution, and potential range are used in the “blank” experiment. The current densities resulting from electrolysis of 10−2 M solutions cause inhomogeneity of the potential in the metal film electrode. The iR drop in the film was measured with new and used films and it was found that when a narrow strip of a new film was used as an electrode, the potential inhomogeneity was practically eliminated, and thus the interpretation of “optical slope” experiments became easier. An Electro-IRS experiment was used for following changes in the concentration of a cation-radical intermediate at an electrode surface, during a stepwise electron removal process. The radical could be monitored by IRS in cases where the current-potential curve did not show two separate oxidation steps. The equilibrium constant for the formation of the radical from the fully oxidized and reduced forms could be estimated from the ΔR/R vs. E curve. The population of absorbing molecules in an adsorbed layer is, sometimes, much larger than their population in the solution region into which the evanescent wave penetrates. The result may be a predominant contribution of the adsorbed layer to IRS reflectance changes. This situation, demonstrated for malachite green oxidation, can be used for observing adsorbed layers during a faradaic process, without interference from the latter.
The measuriment of ferromagnets magnetic characteristics using Labview software
The digital method of measurement and registration of dynamic loops hysteresis family of magneto-soft materials where, along with known analogues from electro-technical steel, magnetic materials with considerably smaller specific magnetic losses such as amorphous alloys on the basis of iron, is offered. Tests of magnetic properties of materials are carried out on the base of the hardware-software measuring complex in which along with the standard established electric equipment and USB oscillograph for realization of a digital method, the software for the personal computer developed in the environment of visual programming of Borland Delphi 7.0, connected through the ActieveX technology with the Labview 7.0 environment, is applied. The software allows carrying out input of basic data concerning geometry of prototypes of cores from magnetic materials and numbers of rounds of the magnetizing and measuring windings located on their surface. Experimental data on voltage at measuring winding terminals are processed by means of the virtual integrator in a Labview package. The developed software provides the possibility of saving the obtained hysteresis loop in the form of a text file, and creation of the hysteresis loops family on the virtual oscillograph screen.