Electrode preparation apparatus

A neat form of apparatus much smaller than Kohl-rausch s, consists of an ebonite cup and rod fitted with platinum electrodes prepared in the usual manner. The rod can be moved vertically over the cup by means of micrometer screws, and the distance between the electrodes read off on a divided scale by a vernier. Quantities of solutions as small as 3 cc maybe employed. 

Tiselius (1938a) also constructed a special preparative apparatus for large-scale preparations. It was built after the same principles as the analytical model, but with ten times greater dimenaons. This apparatus is shown in Fig. 25. The U-tube consisted of a bottom cell, four intermediate sections, and a top cell. The cross-section area of the TJ-tube was 7.5 cm. The electrode tubes were of 5-1. capacity each due to thdr large dimendons, they were kept outside the refrigerating bath. The coimection tubes between U-tube and electrode tubes were bent as shown in the figure in order to prevent the colder and heavier solution in the U-tube from falling down into the electrode tubes if it did, it would stir up the chloride solution around the electrodes. 

The polarographic apparatus, reference electrodes, supporting electrolytes, solvent preparation, and preparation of the carbenium-ion solutions have been described in references 1-11 and 20. It is noteworthy that the reference electrode [9] described in 1978 maintained its EMF of -0.130 versus SCE until accidentally broken in 1983. 

The chemistry of fluorine is dominated by its electronegativity, which is the highest of all elements. The colorless gas F2 has an estimated standard electrode potential E° (Chapter 15) of +2.85 V for reduction to F (cf. + 1.36 V for Cl2 to Cl-), and thus F2 immediately oxidizes water to oxygen (E° = +1.23 V), and 2% aqueous NaOH to the gas F20. Obviously, F2 cannot be made by electrolysis of aqueous NaF. The usual preparation involves electrolysis of HF-KF melts in a Monel (Cu-Ni alloy) or copper apparatus. 

In general, in an electrolytic process, oxygen is evolved at the anode, and hydrogen at the cathode. If these electrodes are in different compartments, with a suitable electrolyte we may expect to have reactions of oxidation taking place in the anode compartment and reactions of reduction in the cathode compartment. In inorganic chemistry, the more successful electrolytic preparations are chiefly those of oxidation while in organic chemistry, reactions of both oxidation and reduction are often successful. In inorganic chemistry, reactions of reduction are usually effected in simple ways. The several units of the necessary apparatus are connected as shown in Fig. 10. 

The apparatus for this preparation consists of a narrow glass beaker, or a wide-mouthed bottle. The beaker is corked, and an efficient glass stirrer passing through the centre is attached to a small turbine or motor. Pour electrodes are fixed in position so that they are clear of the stirrer. Two anodes, each of sheet platinum of about 1 sq. dcm. surface, are placed diametrically opposite one another, while the two cathodes, spirals of platinum wife and each of 2 cms. surface, are placed between them near the sides of the beaker. 50 gms. toluene, 200 c.cs. of 10% sulphuric acid and 250 c.cs. of acetone are placed in the cell, which is surrounded by cold water. The current density should be 1-5—2 amperes, the E.M.F. 5—6 volts, and the temperature at 15°—20°. The stirring must be vigorous to keep the mixture in a thorough emulsion. 

Allow the current to flow for about 20 minutes. During the flow of the current, prepare two clean beakers, which should be set side by side on the desk, near the apparatus also have a wash bottle at hand. As soon as the current is turned off, place the iron electrode in one of the beakers set the carbon pole aside. Pour the solution out of the electrolytic cell, holding it so that the cathode arm will empty into the beaker containing the iron cathode,... 

The present procedure offers an alternative electrochemical setup to accomplish the Kolbe electrolysis of half esters to that reported earlier for the preparation of dimethyl octadecanedioate.17 In the present case the apparatus offers general versatility and electrode coating is prevented by an additive (pyridine). In the earlier case periodic current reversal was necessary. 

Electrochemical polymerisation offers a number of advantages. The apparatus is simple, a cell with working, counter and reference electrodes operated at either constant potential or constant current. Insoluble polymers can either be prepared as films directly on to a variety of electrodes or be incorporated into a porous layer situated on the working electrode. The film can be reduced and... 

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