Platinum electrodes and

Platiaum and its alloys are also used as biomedical electrodes, eg, platiaum—indium wires for permanent and temporary pacemaker leads and defibrillator leads. Electrophysiology catheters, which contain platinum electrodes and marker bands, have been used to map the electrical pathways of the heart so that appropriate treatment, such as a pacemaker, can be prescribed. 

Oxidation-reduction potential Because of the interest in bacterial corrosion under anaerobic conditions, the oxidation-reduction situation in the soil was suggested as an indication of expected corrosion rates. The work of Starkey and Wight , McVey , and others led to the development and testing of the so-called redox probe. The probe with platinum electrodes and copper sulphate reference cells has been described as difficult to clean. Hence, results are difficult to reproduce. At the present time this procedure does not seem adapted to use in field tests. Of more importance is the fact that the data obtained by the redox method simply indicate anaerobic situations in the soil. Such data would be effective in predicting anaerobic corrosion by sulphate-reducing bacteria, but would fail to give any information regarding other types of corrosion. 

The redox potential is determined with a probe consisting of a platinum electrode and a Hg/Hg2Cl2 Cl or Ag/Ag Cl—Cl reference electrode. If Ep is the potential of the platinum probe, Ej the potential of the reference electrode and tne redox potential of the soil (in mV on the hydrogen scale) then... 

Fig. 19.16 Schematic E — I diagrams of local cell action on stainless steel in CUSO4 + H2SO4 solution showing the effect of metallic copper on corrosion rate. C and A are the open-circuit potentials of the local cathodic and anodic areas and / is the corrosion current. The electrode potentials of a platinised-platinum electrode and metallic copper immersed in the same solution as the stainless steel are indicated by arrows, (a) represents the corrosion of stainless steel in CUSO4 -I- H2 SO4, (b) the rate when copper is introduced into the acid, but is not in contact with the steel, and (c) the rate when copper is in contact with the stainless steel...

No experiments appear to have been made with such cells, although the equation has been verified with oxygen at different partial pressures in admixture with nitrogen, with platinum electrodes and hot solid glass as electrolyte (Haber and Moser). A similar case is that of two amalgams of a metal, of different concentrations, as electrodes, and a solution of a salt of the metal as electrolyte (G. Meyer, 1891). Here we must take the osmotic pressures of the metals in the amalgams, Pi, P2, and, for an 7i-valent metal ... 

A prepassivated platinum electrode and an electrode of the metal of interest have been used to follow the development of a biofilm to determine its effects on the corrosion behavior of structural materials. The time dependence of the open circuit potential of several stainless steels... 

Specific types of consumable electrode are designated in terms of the constituent material (e.g., as a silver electrode ). Nonconsumable electrodes are designated either in terms of the electrode material or in terms of the chief component in the electrode reaction for instance, the terms platinum electrode and hydrogen electrode are used for electrode (1.27). Neither of these names completely describes the special features of this electrode. 

Lee C-W, Compton RG, Eklund JC et al (1995) Mercury-electroplated platinum electrodes and microelectrodes for sonoelectrochemistry. Ultrason Sonochem 2 S59-S62... 

Zhan [61] reported the use of an oscillopolarographic method for the determination of primaquine phosphate and other drugs in pure form and in pharmaceutical preparations. The sample solution was mixed with potassium bromide and 6 M hydrochloric acid and the mixture was titrated with 0.1 M sodium nitrite. A micro platinum electrode and a platinum electrode were used as indicators and reference electrodes, respectively. The mean recoveries were 96.88-99.88%. Results agreed well with those obtained by the Chinese Pharmacopoeia method. 

CE, another high performance separation technique, was also proved to be a powerful tool and an alternative for HPLC in the analysis of natural dyestuffs, even if its application in this field is still considerably limited. It could play an important role especially in the analysis of artworks, as it requires a very small volume of a sample solution (a few dozen nanolitres). In CE[ 10 14] separation of charged species is based on their different migration properties along the capillary tube which is in a constant electric field. Two platinum electrodes and both ends of a narrow bore (i.d. 25 100 pm) flexible fused silica capillary (usually 60 100 cm long) filled with a suitable conducting buffer are immersed in two... 

A method for electroanalytical determination of lead traces in gasoline is based on an apparatus consisting of a glassy carbon electrode, a platinum electrode and a standard... 

For titrations involving those species, the response can be improved by forming a cell from a pair of identical platinum electrodes and passing a very small constant current ( 5 pA) between them throughout the titration. As electrolysis is negligible, the solution composition is virtually unaffected by the passage of the current. The break in the titration curve is usually sharp and can be 100-200 mV or more. The use of a pair of platinum electrodes may be particularly advantageous if contamination of the sample... 

The platinum electrode and LSM s were modified with Ru and Os polymers respectively as described in the experimental section. Each sample was rinsed with acetone and placed in an acetonitrile/0.1M TBAP solution and a... 

Part—III exclusively treats Electrochemical Methods invariably and extensively used in the analysis of pharmaceutical substances in the Official Compendia. Two important methods, namely potentiometric methods (Chapter 16) deal with various types of reference electrodes and indicator electrodes, automatic titrator besides typical examples of nitrazepam, allopurinol and clonidine hydrochloride. Amperometric methods (Chapter 17) comprise of titrations involving dropping-mercury electrode, rotating—platinum electrode and twin-polarized microelectrodes (i.e., dead-stop-end-point method). 

Measnrements of Ea are usually made with a platinum electrode placed in the soil solntion together with a reference half cell electrode of known potential. The platinnm electrode transfers electrons to and from the soil solution withont reacting with it. Reducing half reactions in the soil tend to transfer electrons to the platinum electrode and oxidizing half reactions to remove them. At eqnilibrinm no electrons flow and the electric potential difference between the half cell comprising the platinnm electrode and the soil solntion and the half cell comprising the reference electrode is recorded. 

V-Acylsaccharins prepared by treatment of the sodium salt of saccharin with acyl chlorides were reduced by 0.5 molar amounts of sodium bis(2-methoxyethoxy)aluminum hydride in benzene at 0-5° to give 63-80% yields of aliphatic, aromatic and unsaturated aldehydes [1108 Fair yields (45-58%) of some aliphatic aldehydes were obtained by electrolytic reduction of tertiary and even secondary amides in undivided cells fitted with platinum electrodes and filled with solutions of lithium chloride in methylamine. However, many secondary and especially primary amides gave 51-97% yields of alcohols under the same conditions [130]. 

Only three values of log Kso are available for lepidocrocite and these are not in very good agreement. Hashimoto and Misawa (1973) measured the solubility of lepidocrocite produced by anodic deposition from Fe" solution on a platinum electrode and obtained a value for log Kso of 2.50. This agrees with the value calculated from the free energy of formation (Blesa et al., 1994). Mohr et al. (1972) quote a value of 2.72 and Lindsay (1979) gives 1.59. 

In a subsequent study by Robertson, Murphy, and coworkers, polymer 23 was synthesized by anodie polymerization on platinum electrodes and eompared to polymer 19 in order to determine the effect of the position of the linkage of the dithiolene to thiophene moieties. In this study, the researchers used the salts [Bu4N][ll] and [Bu4N][16] in MeCN to prepare the respective polymers 19 and 23. Surprisingly, the polymerization of the anion 11 resulted in films exhibiting different electroehemieal response than that observed for 19... 

The process is operated at a platinum electrode and a reduced efficiency due to side reactions is observed. A maximum yield of 55% is reported. The use of in situ generated NBS and bromine for the synthesis of nucleosides from silylated pyrimidines has been studied. Nokami etal. [125] suggest the use of only catalytic amounts of NBS or bromine and regeneration of the catalyst by anodic electrolysis in an undivided cell system. 

To prepare metal hexacyanoferrate films, very frequently the following procedure was followed first a film of the respective metal, for example, cadmium [79], copper [80], silver [81], or nickel [82, 83] was elec-trochemically plated on the surface of a platinum electrode, and that was followed by chemical oxidation of the metal film in a solution of K3[Fe(CN)6], leading to the formation of the metal hexacyanoferrates. The same method has been used to produce films of nickel hexacyanoruthen-ate and hexacyanomanganate using the appropriate anions [83]. It is also possible to perform the oxidation of the deposited metals in solutions containing hexacyano-ferrate(II) by cyclic oxidation/reduction of the latter. In a similar way, films of copper heptacyanonitrosylferrate have been deposited [84]. 

Standard Hydrogen Electrode standard electrode consisting of hydrogen gas at 1 atmosphere pressure, a platinum electrode, and 1 molar hydrochloric acid, the potential of this electrode is defined as 0 and is used to determine the potential of other halfreactions... 

Table 8 Peak potentials at the platinum electrode and standard potential for the oxidation of X-Ph-S in DMF/0.1 M TBAP at 25°C."...

Electrolysis of such solutions with platinum electrodes and with low current densities yields polysulphides with higher current densities sulphates and dithionates are formed.5... 

Figure 2 Electron-transfer series [Fe4S4(SPh)4]4-/3-/2-h- (3.8 mmol dm-3) in 3 1 to)uene [NBu4][BF4] at 23 °C, using platinum electrode and scan rate of 0.1 V s-1...

---