Alkali metal amalgam, solid

The theoretical treatment presented (Eqs 4.1-4.5) is applicable also for direct wet electrochemistry on Pt cathode in aprotic electrolyte solution [12,13] (Table 4.1) and for some other chemical reductants, Rj, viz. benzoin dianion [14] and sodium dihydronaphthylide [15] (Table 4.1). Apparently, the decision between chemical and electrochemical carbonization may not be straightforward. The latter scenario requires a compact solid electrolyte with mixed electron/ion conductivity to be present at the interface. This occurs almost ideally in the reactions of solid fluoropolymers with diluted alkali metal amalgams [3]. If the interfacial layer is mechanically cracked, both electrochemical and chemical carbonization may take place, and the actual kinetics deviates from that predicted by Eq. 4.4 [10]. There is, however, another mechanism, leading to the perturbations of the Jansta and Dousek s electrochemical model (Eq. 4.4). This situation typically occurs if gaseous perfluorinated precursors react with Li-amalgam [4,5], and it will be theoretically treated in the next section. 

Ion solvation has been studied extensively by potentiometry [28, 31]. Among the potentiometric indicator electrodes used as sensors for ion solvation are metal and metal amalgam electrodes for the relevant metal ions, pH glass electrodes and pH-ISFETs for H+ (see Fig. 6.8), univalent cation-sensitive glass electrodes for alkali metal ions, a CuS solid-membrane electrode for Cu2+, an LaF3-based fluoride electrode for l , and some other ISEs. So far, method (2) has been employed most often. The advantage of potentiometry is that the number and the variety of target ions increase by the use of ISEs. 

Table 17-1 showed that there is a large overpotential for reduction of H+ at the Hg surface. Reactions that are thermodynamically less favorable than reduction of H+ can be carried out without competitive reduction of H+. In neutral or basic solutions, even alkali metal (Group 1) cations are reduced more easily than H+. Furthermore, reduction of a metal into a mercury amalgam is more favorable than reduction to the solid state ... 

An attack on a C-F bond may operate in the corrosion of poly(tetrafluoroethy-lene) (PTFE) the reaction of PTFE with amalgams of Li, Na, and K has been suggested [66] to proceed by an electrochemical mechanism in the solid phase, with the alkali metal... 

The only directly accessible metal fulminates are those of mercury(II) and silver(I), very dangerously exposive solids obtained by the action of nitric acid and ethanol on the metals or their salts. Most modern preparations of fulminato complexes involve the conversion of a known amount of mercury fulminate into aqueous sodium fulminate by the action of sodium amalgam and ice-cold water the sodium fulminate solution is then allowed to react with the appropriate amount of a transition metal salt, and the resulting complex fulminato ion is precipitated as the salt of a large cation, most frequently Ph4As+ or R4N+ these are not explosive,4,35 Alkali and alkaline earth metal salts containing complex fulminato anions may be isolated from aqueous solutions, but they are reported to be as exposive as the binary silver and mercury fulminates, and are therefore usually avoided. 

These processes differ by the reaction which occur at the cathodes. At a solid cathode which is generally made of iron, hydrogen ions are discharged and simultaneously alkali hydroxide is formed in the electrolyte. At the mercury cathode metallic sodium or potassium is deposited which forms amalgam. This intermediary product is subsequently decomposed by water in a separate compartment whereby hydroxide and hydrogen are obtained while the liberated (denuded) mercury is returned into the electrolytic cell. 

All the arsinic acids dealt with in the following pages arc crystalline solids. Some of tlie primary acids, when heated above their melting-points, eliminate water and form anliydrides. The acids are very stable but may be reduced by amalgamated zinc dust and hydrochloric acid, or by electrolysis in aqueous alcoholic hydrochloric acid, to arylarsines, RAsIIs- An exception to tlie above-mentioned stability is the case of benzylarsinic acid, which is decomposed by mineral adds, and differs from all other members of this series in its reactions. The salts formed with alkali and alkaline earth metals show that the acids are dibasic. Esters may be formed by heating the silver salts of tlie acids in ethereal solution under reflux with the calculated amount of alkyl iodide, but excess of the latter must be avoided or alkyi-arylarsenites are formed ... 

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