Electrolysis of solutions

Kolbe reaction The pre >aration of saturated or unsaturated hydrocarbons by the electrolysis of solutions of the alkali salts of aliphatic carboxylic acids. Thus, ethanoic acid gives ethane,... 

Electrolysis of solutions containing Au(CN)2 is widely used to recover gold from solution (electrowinning) [17]. The process is also used to deposit gold coverings for electrons (e.g. printed circuit boards, electrical connectors) and most recently for hip and shoulder joint replacement surgery. 

Methods have been developed for perchloric acid synthesis which involve the electrolysis of solutions containing hydrogen chloride or molecular chlorine. These processes occur at high anode potentials (2.8 to 3.0 V vs. SHE), when oxygen is evolved at the anode in parallel with perchloric acid formation. The current yields of perchloric acid will increase considerably when the reaction is conducted at low temperatures (e.g., 20°C). 

More particularly, a serious breakthrough was achieved in the methods of electrochemical calorimetty. Initial conclusions as to anomalous heat evolution during the electrolysis of solutions prepared with heavy water were caused by an incorrect formulation of control experiments in light water. In fact, none of the communications confirming anomalous heat evolution have been free of procedural errors, so that one cannot even discuss a sporadic observation of this effect. In contrast to all other experimental manifestations, heat evolution is indicative of any possible nuclear transformation, which implies that in its absence, neither reaction (33.4.1) nor reaction (33.4.2) can be suggested to occur. 

Case II Reversible or Ouasi-Reversible Redox Species. If the tip-sample bias is sufficient to cause the electrolysis of solution species to occur, i.e., AEt > AEp, ev, the proximity of the STM tip to the substrate surface (d < 10 A) implies that the behavior of an insulated STM tip-substrate system may mimic that of a two-electrode thin-layer cell (TLC)(63). At the small interelectrode distances required for tunneling, a steady-state concentration gradient with respect to the oxidized (Ox) and and reduced (Red) electroactive species should be established between the tip and the substrate, and the resulting steady-state current will augment that present as a result of the convection of electroactive species from the bulk solution. In many cases, this steady state current is predicted to overwhelm the convective currents, so this situation is of concern when STM imaging under electrochemical conditions (64). 

Figure 10. COD evolution as a function of electrolysis time for electrolysis of solutions containing 50 mMNa2S04 + 1 mMFe + dye (a) 0.082 mMDR23, (b) 0.25 mM A07, (c) 0.33 mM Am, (d) 0.1 mM AG25, (e) 0.1 mM Am, (f) 0.17 mM BB9. Electrolyses were carried out in a membrane cell with a reticulated vitreous carbon cathode (5 cm x 5 cm x 1 cm).

The principal characteristics of this method are the electrolysis of solutions of organic compounds using electrodes of platinum or graphite at anode potentials below those which could give rise to the evolution of elemental fluorine. 

Metal is plated out in the electrolysis of solutions of metal salts, other than those of the alkali and alkaline earth metals (and iron and aluminum). For example, in the electrolysis of a ZnCl2 solution, we would obtain metallic zinc,... 

The electrolysis of solutions of organic compounds in anhydrous hydrogen fluoride under conditions where no free fluorine is produced. 

G. Janeceks observed that spontaneously inflammable phosphine is evolved during the electrolysis of solutions of the metaphosphates. S. Arrhenius, in his thesis Recherches sur le conductibUite galvanique des electrolytes (Stockholm, 1884), gave measurements of the electrical resistance, and the electrical conductivity of the acid. E. B. R. Prideaux found the meta-acid has a greater conductivity than... 

A modification of the electrolytic method involves the electrolysis of solutions containing both the metallic and the mercuric ions. This procedure should possibly lead to the deposition of amalgams of varying composition, but no extensive study of this sort has ever been reported. Bismuth and copper amalgams have been prepared in this manner. 

The existence of highly oxidised salts of sulphuric acid was first demonstrated by H. Marshall1 when investigating the result of electrolysis of solutions of potassium sulphate in well-cooled sulphuric acid. He succeeded in preparing potassium and ammonium persulphates, and he ascribed the formula M2Sj08 to these compounds. 

This theory accounts for the dependence between the current efficiency and the concentration of HSO ions present in the solution. It cannot explain, however, why the yields at the electrolysis of solutions of sulphates, in which the concentration of HSO ions is very low, are even greater than when electrolysing solutions of sulphuric acid alone or its mixture with a sulphate. This deficiency is not found in the recent explanation of the reaction mechanism, according to which the sulphate ions SO - are primarily oxidized by hydrogen peroxide or by hydroxyl radicals formed, according to equations ... 

In the electrolysis of solutions of alkali hydroxides under suitable conditions, hydrogen peroxide is produced at the anode by the combination of the discharged hydroxyl ions. 

In contradistinction to ozone, hydrogen peroxide is not produced during the electrolysis of solutions of fluorides.4... 

The same relative oxidation power was found for the above methods in the degradation of all aromatics, as deduced from the percentages of TOC removal after 3 h of electrolysis of solutions with lOOmgdm-3 TOC of 4-CPA, MCPA, 2,4-D, and 2,4,5-T at pH 3.0 and 100 mA given in Table 19.2. All initial chlorine of these compounds was released as Cl-, which remained stable in solution. The apparent current efficiency (ACE) for these trials was then calculated from the following equation ... 

Electrowinning — The extraction of metals from their compounds by - electrolysis of solutions containing the metal ions. Usually electrowinning refers to mass production of metals from their ores after dissolution in appropriate medium, or in molten salts at high temperatures. The basis of electrowinning is electrolysis, in which the produced metal is plated on the cathode of... 

The electrolysis of solutions of lithium chloride in various solvents, such as water, alcohols, glycerol, and phenol, has been investigated by Patten and Mott.9... 

Preparation.—Being very sensitive to rise of temperature, the isolation of the ammonium radical by the electrolysis of solutions of ammonium salts in liquid ammonia is probably precluded by the thermal effect of the current. Its formation by the interaction of well-cooled ammonium chloride and a solution of potassium in liquid ammonia at —70° C. is indicated by a deficit of as much as 65 per cent, in the volume of the hydrogen evolved.1... 

Thus, owing to the endothermic character of the H" ion, only the most electropositive metals—the alkalis and the alkaline earths—form saline or saltlike hydrides, such as NaH and CaH2. The ionic nature of the compounds is shown by their high conductivities just below or at the melting point and by the fact that on electrolysis of solutions in molten alkali halides hydrogen is liberated at the anode. 

In the electrolysis of solutions of M(S04)2 dHyO, protons move toward the cathode and the metal to the anode, so these compounds can be formulated as H2[M0(S04)2] -3H20 (disulfatozirconic and -haftiic acids). The reaction of sodium acetate with Zr0Cl2-8H20 yields diacetatozirconic acid (equation 9). They do not precipitate with acid dyes, and they react with anion exchange resins rather than with their cation exchange counterparts. 

The oxidation of substituted aromatic amines with silver(l) carbonate on Celite has been shown to yield symmetrically substituted phenazines, albeit in poor yields. 2,7-Dimethoxy-hexafluorophenazine has been obtained upon electrolysis of solutions of 4-methoxytetrafluoro-aniline, and oxidative coupling of benzene-1,4-diamine with aniline or substituted anilines also gives phenazine derivatives. ... 

Electrochemical Behaviour.— The electrolysis of solutions containing uranium compounds has not been fully investigated, but in generM the product at the cathode appears to consist of hydrated oxides in various stages of oxidation. This is the case even when a... 

As a consequence, electrolysis of solutions containing aluminum alkyl must be conducted in the absence of oxygen and water in a sealed apparatus under an atmosphere of inert gas. For technical electrolysis cells, nitrogen is generally used, due to its lower cost. The charging and removal of electrodes must be conducted via a lock system, which prevents the admission of air and moisture. Furthermore, all pieces which are to be brought into the electrolytic cell must be completely dried. 

Derivation (1) Electrolysis of solutions in hydrogen fluoride (Simons process) (2) replacement of chlorine or bromine by fluorine with hydrogen fluoride in the presence of a catalyst (antimony trifluoride or pentafluoride) (3) addition of hydrogen fluoride to olefins or acetylene. 

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