Electrolyte decomposition

Early demand for chlorine centered on textile bleaching, and chlorine generated through the electrolytic decomposition of salt (NaCl) sufficed. Sodium hydroxide was produced by the lime—soda reaction, using sodium carbonate readily available from the Solvay process. Increased demand for chlorine for PVC manufacture led to the production of chlorine and sodium hydroxide as coproducts. Solution mining of salt and the avadabiHty of asbestos resulted in the dominance of the diaphragm process in North America, whereas soHd salt and mercury avadabiHty led to the dominance of the mercury process in Europe. Japan imported its salt in soHd form and, until the development of the membrane process, also favored the mercury ceU for production. 

Pkctrolysis of HCl Electrolytic decomposition of aqueous HCl to generate CI2 and H2 foHows the overaH reaction... 

Because the electrolyte contains excess alkaH which could cause spontaneous decomposition of the hydrogen peroxide, the H2O2 in the product... 

Examples of similar processes are the decomposition of precipitated aluminum trHiydroxide to alumina, which is the feed for the electrolytic production of aluminum metal, and the drying of wet sulfide concentrates in preparation for flash roasting (see Aluminumand aluminum alloys). 

The electrolytic decomposition of alumina yields oxygen which reacts with the carbon anode for an overall cell reaction ... 

In atomization, a stream of molten metal is stmck with air or water jets. The particles formed are collected, sieved, and aimealed. This is the most common commercial method in use for all powders. Reduction of iron oxides or other compounds in soHd or gaseous media gives sponge iron or hydrogen-reduced mill scale. Decomposition of Hquid or gaseous metal carbonyls (qv) (iron or nickel) yields a fine powder (see Nickel and nickel alloys). Electrolytic deposition from molten salts or solutions either gives powder direcdy, or an adherent mass that has to be mechanically comminuted. 

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). 

The cell is the basis of all electrolysis. The anode admits current into the electrolyte and the cathode serves as a means of exit for the electrical current. The electrical flow provides a definition for electrolysis the flow of current from the anode through the electrolyte and out of the cell through the cathode with ensuing decomposition of the electrolyte, with products being formed at the electrodes. 

The intermediate HCIO2 is rapidly oxidized to chloric acid. Some chlorine dioxide may also be formed. Kinetic studies have shown that decomposition to O2 and chloric acid increase with concentration, temperature (88), and exposure to light (89—92), and are pH dependent (93). Decomposition to O2 is also accelerated by catalysts, and decomposition to chlorate is favored by the presence of other electrolytes, eg, sodium chloride (94—96). 

Hydrogen Liquefaction. Hydrogen can be produced from caustic—chlorine electrolytic cells, by decomposition of ammonia or methanol, or by steam—methane reforming. Hydrogen recovered by these methods must be further purified prior to Hquefaction. This is generally achieved by utilizing pressure swing adsorption methods whereby impurities are adsorbed on a soHd adsorbent. 

Electric current passing through a metal joint having a moisture content causes electrolysis of water vapour. Copper, being a galvanic metal, forms an electrolytic circuit with other metals and decomposes the joint. Decomposition is corroding and erodes the aluminium metal. 

Molten halides are liquid electrolytes in many instances, and their decomposition may be canned out in principle to produce the metal and halogen, usually in the gaseous state. The theoretical decomposition voltage, E°, is calculated from the Gibbs energy of formation tlrrough the equation... 

The charge state of the cell must be maintained in operation to have a cell voltage of 0.9 to 1.2 V [6]. Overcharging the cell is to be avoided due to electrolytic decomposition of water and evolution of gas. The cell voltage should therefore not exceed 1.4 V. Cathodic protection stations should be operated so that the cell voltage lies in the desired range. 

Electrolytic process A process that causes the decomposition of a chemical compound by the use of electricity. 

The oxidation of hydrogen to water (Hj -t- i Oj -> HjO) is thermodynamically spontaneous and the energy released as a result of the chemical reaction appears as heat energy, but the decomposition of water into its elements is a non-spontaneous process and can be achieved only by supplying energy from an external source, e.g. a source of e.m.f. that decomposes the water electrolytically. Furthermore, although the heat produced by the spontaneous reaction could be converted into electrical energy, the electrical... 

The process used to prepare fluorine was developed by Henri Moissan in Paris more than a century ago it won him one of the early (1906) Nobel Prizes in chemistry. The electrolyte is a mixture of HF and KF in a 2 1 mole ratio. At 100°C, fluorine is generated by the decomposition of hydrogen fluoride ... 

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