Electrolytic cleaning procedures

Lead alloys Preferably use the electrolytic cleaning procedure just described. Alternatively, immerse for 5 min in boiling 1% acetic acid. Rinse in water to remove the acid and brush very gently with a soft bristle brush to remove any loosened matter. 

Iron and steel Preferably use the electrolytic cleaning procedure, or else immerse in Clark s solution (hydrochloric acid 1(X) parts, antimonious oxide... 

Electrolytic Cleaning Procedures for Removal of Corrosion Products ... 

First, following a cleaning procedure, electrochemical deposition was carried out using an aqueous solution with PdS04 electrolyte, citric add, and boric acid (25 °C ... 

Twenty-two copper-based coins of the Roman Republic were analyzed for Fe, Co, Ni, Cu, Zn, As, Ag, Sn, Sb, and Pb by using X-ray fluorescence according to the procedures described by Carter and Booth (11). Generally, X-ray fluorescence determines elements only in a thin surface layer, about 5-10 xm deep, so it was necessary to clean coins for analysis in such a way that the surface layer was as representative of the entire coin as possible. First, the coins were cleaned by electrolytic reduction in a hot solution of sodium carbonate. Next, the coins were abraded in an air stream containing finely divided aluminum oxide powder to remove about 10 to 15 xm of metal. Carter and Booth described the cleaning procedure in detail as well as the X-ray fluorescence parameters (11). 

Prior to evacuation the surface was rinsed with a solution containing 0.1 M KF adjusted to pH = 4 with HF. Water used in the experiments was pyrolytically distilled in pure O2 through a Pt gauze catalyst at 800 C, arid once morie distilled. An experiment was performed from time to time in which the sample was immersed into a blank solution consisting of pure electrolyte, rinsed, evacuated and analyzed. Purification and cleaning procedures were continued until all impurities detectable by Auger spectroscopy were consistently absent. 

Platmmn electrodes were cleaned with the same procedure. Ihen the electrol3rte was replaced with an electrolsrte containing 0.01 M tin (II). This electrolyte was prepared immediately before the experiment by dissolving tin (n> chloride (Johnson Matthey, 99.999%) in 3 M sulfuric add. 

One of the most common sources of contamination is the electrolyte since impurities in it would diffuse to the electrode and adhere to it during the course of the experiment. Impurities in the electrolyte can be reduced substantially by careful purification of solvent and solute. Distillation or ultrafiltration purifies water, the most common solvent. Usually solute materials can be bought in a very high purity, and whenever this is not the case, they can be cleaned by standard procedures such as recrystallization or calcination. Electrolysis of the electrolyte is also a common practice. Here, two sacrificial electrodes are immersed in the electrolyte and a potential is applied between them for about 36 hr in such a way that impurities are oxidized or reduced on their surfaces—the electrodes act as a garbage disposal thus the name of sacrificial electrodes. 

Procedure. The solutions to be studied are the strong electrolyte HCl and weak electrolyte monochloroacetic acid, each at two concentrations—roughly 0.25 and 0.125/ 3. About 150 mL of each solution will be needed, and the 0.125/n solutions required should be prepared by diluting the 0.25m stock solutions with distilled water. Place each solution in a clean, glass-stoppered flask packed in crushed ice. A flask of distilled water should also be packed in ice. 

Preparing a clean surface is often a prerequisite for surface-science studies. UHV-based methods of sample preparation and characterization are established, and these may be exploited for studies of surfaces immersed in solution by interfacing an electrochemical cell with an UHV chamber. Samples can then be transferred from UHV and immersed into electrolyte solution under a purified-Ar atmosphere. However, even under these clean conditions, some metals oxidize or get contaminated prior to immersion. Other techniques for the preparation of clean surfaces that do not require UHV techniques are available for some metals. For example, flame annealing and quenching have been successfully used, but this procedure is probably limited to Au, Pt, Rh, Pd, Ir, and Ag substrates. In this technique, substrates are annealed in an oxygen flame and quenched in pure water. 

In the case of Pt(l 11), voltammograms for flame-cleaned electrodes were obtained under UHV conditions [53] providing evidence that such voltammograms correspond to well-ordered (lxl) structures. Since the same voltammetric features were obtained with various surface preparation procedures, there is a large stability of the (111) (lxl) structure [60], Conversely, UHV studies have shown the existence of various surface structures for Pt(100) [42] or Pt(110) [61]. Such structural changes may influence the electrochemical response of these orientations. Similar to Pt(lll), voltammograms obtained with Pt(100) electrodes have been found to depart on the electrolyte composition that is, a decrease of the anion-specific adsorption shifts the hydrogen adsorption states to more positive potentials. 

Conventional extraction procedures and evaporation techniques are applied. Depending on the nature of the compounds, different clean-up procedures are recommended ion exchange for amino acids and organic acids, pyridine solutions for sugars. Because the final volume of the solution must be small, evaporations must be carried out in vacuo (Rinco evaporators) or by lyophilization. Sometimes inorganic ions (Na, Mg ) interfere in chromatography, and desalting may have to be carried out. Usually, commercial electrolytic desalters are used for this purpose. 

---