Electrolysis, cell

Electrolysis cell. This is shown in Fig. VI, 31, 1 and is almost self-explanatory. The cylindrical cell of Pyrex glass (6" long by 2 " diameter) is cooled by immersion in a cooling bath. The electrodes consist of two platinum plates (4 cm. X 2-5 cm. X 0-3 mm.), which are placed about 2 mm. apart. The temperature of the electrolyte is maintained at 30-35° by means of the internal cooling coil and also by immersion of the cell in ice-water. A current of 1 5-2 0 amperes is passed until the electrolyte becomes slightly alkaline, which normally takes about 20-50 per cent, longer than the calculated time on the basis of the current and the amounts of acid employed. It is advantageous to reverse the direction of the current occasionally. 

Sebacic acid. Dissolve 40 g. of methyl hydrogen adipate in 100 ml. of absolute methanol to which 01 g. of sodium has been added. Pass a current of about 2 0 amps, until the pH of the solution is about 8 (ca. 5 hours) test with B.D.H. narrow-range indicator paper. Transfer the contents of the electrolysis cell to a 500 ml. round-bottomed flask, render neutral with a little acetic acid, and distil off the methanol on a water... 

Myristic acid from hexanoic acid and methyl hydrogen sebacate). Dissolve 23 -2 g. of redistilled hexanoic acid (re caproic acid), b.p. 204-6-205-5°/760 mm., and 21-6 g. of methyl hydrogen sebacate in 200 ml. of absolute methanol to which 0 13 g. of sodium has been added. Electrolyse at 2 0 amps., whilst maintaining the temperature between 30° and 40°, until the pH is about 8 0 (ca. 6 hours). Neutralise the contents of the electrolysis cell with a little acetic acid and distil off the methyl alcohol on a water bath. Dissolve the residue in 200 ml. of ether, wash with three 50 ml. portions of saturated sodium bicarbonate solution, once with water, dry with anhydrous magnesium sulphate, and distil with the aid of a fractionating column (see under Methyl hydrogen adipate). Collect the re-decane at 60°/10 mm. (3 0 g.), the methyl myristate at 158-160°/ 10 mm. (12 5g.) and dimethyl hexadecane-1 16-dicarboxylate at 215-230°/ 7 mm. (1 -5 g.)... 

Fused Salt Electrolysis. Only light RE metals (La to Nd) can be produced by molten salt electrolysis because these have a relatively low melting point compared to those of medium and heavy RE metals. Deposition of an alloy with another metal, Zn for example, is an alternative. The feed is a mixture of anhydrous RE chlorides and fluorides. The materials from which the electrolysis cell is constmcted are of great importance because of the high reactivity of the rare-earth metals. Molybdenum, tungsten, tantalum, or alternatively iron with ceramic or graphite linings are used as cmcible materials. Carbon is frequently used as an anode material. 

Nonmineralized SGA flows freely, and is often known as sandy alumina because it easily covers the cryoflte bath of aluminum electrolysis cells (see Aluminum compounds, introduction). Properties typical of a sandy SGA are shown in Table 1. Aluminum smelting technology in the United States is primarily based upon sandy alumina. Older European smelting technology, however, is based upon a poor flowing, low bulk density, highly mineralized SGA called floury alumina, composed principally of a-Al O. ... 

Sir Humphry Davy first isolated metallic sodium ia 1807 by the electrolytic decomposition of sodium hydroxide. Later, the metal was produced experimentally by thermal reduction of the hydroxide with iron. In 1855, commercial production was started usiag the DeviUe process, ia which sodium carbonate was reduced with carbon at 1100°C. In 1886 a process for the thermal reduction of sodium hydroxide with carbon was developed. Later sodium was made on a commercial scale by the electrolysis of sodium hydroxide (1,2). The process for the electrolytic decomposition of fused sodium chloride, patented ia 1924 (2,3), has been the preferred process siace iastallation of the first electrolysis cells at Niagara Falls ia 1925. Sodium chloride decomposition is widely used throughout the world (see Sodium compounds). 

Table 6. Tekkosha Fused-Salt Electrolysis Cells ...

The electrolyte thus formed can conduct electric current by the movement of ions under the influence of an electric field. A cell using an electrolyte as a conductor and a positive and a negative electrode is called an electrolysis cell. If a direct-current voltage is appHed to a cell having inert electrode material such as platinum, the hydrogen ions (cations) migrate to the cathode where they first accept an electron and then form molecular hydrogen. The ions... 

Platinum Platinum-coated titanium is the most important anode material for impressed-current cathodic protection in seawater. In electrolysis cells, platinum is attacked if the current waveform varies, if oxygen and chlorine are evolved simultaneously, or if some organic substances are present Nevertheless, platinised titanium is employed in tinplate production in Japan s. Although ruthenium dioxide is the most usual coating for dimensionally stable anodes, platinum/iridium, also deposited by thermal decomposition of a metallo-organic paint, is used in sodium chlorate manufacture. Platinum/ruthenium, applied by an immersion process, is recommended for the cathodes of membrane electrolysis cells. ... 

At the left electrode in Figure 19-5 the halfreaction occurring is Cl- —>- Cl4.g) + e, and at the right electrode the half-reaction is Na+ + er — - Naff). Which electrode is the anode and which is the cathode With these half-reactions, balance the net reaction occurring in the electrolysis cell. 

Cathode. The cathode is the electrode at which reduction occurs. In an electrolytic cell it is the electrode attached to the negative terminal of the source, since electrons leave the source and enter the electrolysis cell at that terminal. The cathode is the positive terminal of a galvanic cell, because such a cell accepts electrons at this terminal. 

Anode. The anode is the electrode at which oxidation occurs. It is the positive terminal of an electrolysis cell or the negative terminal of a voltaic cell. 

The effect of temperature has already been referred to the electrolysis cell should be immersed in a thermostat bath maintained within 0.2 °C for many purposes a temperature variation of 0.5 °C is permissible. A temperature of 25 °C is usually employed. 

Progress in the development of solid electrolytes is also being achieved from advances in several other fields of technology such as fuel and electrolysis cells, thermoelectric converters, electrochromic devices, and sensors for many chemical and physical quantities. 

The quantity, Q, of electricity passed through the electrolysis cell is measured in coulombs. It is determined by measuring the current, I, and the time, f, for which the current flows and is calculated from... 

The annual production of aluminum in the United States in 2000 was 3.6 Mt (1 Mt = 1.0 X 109 kg). What mass of carbon, lost from the anode of the electrolysis cell, was required to produce this amount of aluminum by the Hall process ... 

Figure 3. Controlled-potential electrolysis cell for generation of radical ions in the cavity of esr spectrometer [from (16) by permission of the authors and the American Chemical Society]. 

Figure 21-4 shows a schematic representation of an electrolysis cell for aluminum production. An external electrical potential drives electrons into a graphite cathode, where Al ions are reduced to A1 metal ... 

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