Sodium hydroxide electrolytes

Figure 10. Current-time response for successive 10 pM additions of histidine (A), asparagine (B), and methionine (C) at unmodified (a) and SWCNT-modified (b) glassy carbon electrodes. Operating potential + 0.55 V supporting electrolyte sodium hydroxide (O.IM, pH 13) stirring rate 300 rpm. From reference 80.

In dissolving electrolytic sodium hydroxide as shipped in drums ordinarily some holes are punched in the drum and it is hung in the upper part of the tank of water. The dissolution will be fairly rapid due to the fact that the concentrated liquors being heavier than water sink, thus causing a circulation. This method is ordinarily slow and unless the material goes into solution very rapidly would not be applicable. 

An additional source of sodium carbonate occasionally used is via the carbonation of electrolytic sodium hydroxide as it is formed in the cell, or separately, later (e.g., [26]). The precipitated sodium hydrogen carbonate is calcined to obtain sodium carbonate in a maimer similar to the last step of the Solvay process (Eq. 7.15). 

ELECTROLYTIC SODIUM HYDROXIDE, CHLORINE. AND RELATED COMMODITIES... 

Industrial Bases by Chemical Routes. -Electrolytic Sodium Hydroxide and Chlorine and Related Commodities. - Sulfur and Sulfuric Add. - Phosphoms and Phosphoric Add. - Ammonia, Nitric Add and their Derivatives. - Aluminium and Compounds. - Ore Enrichment and Smelting of Copper. - Production of Iron and Steel. - Production of Pulp and Paper. -Fermentation Processes. - Petroleum Production and Transport. - Petroleum Refining. - Formulae and Conversion Factors. - Subject Index. 

The Arrhenius definitions and those of Brpnsted and Lowry are essentially equivalent for aqueous solutions, although their points of view are different. For instance, sodium hydroxide and anunonia are bases in the Arrhenius view because they increase the percentage of OH ion in the aqueous solution. They are bases in the Brpnsted-Lowry view because they provide species (OH from the strong electrolyte sodium hydroxide and NH3 from ammonia) that can accept protons. ... 

Properties GVCS-63 3 cl. liq. sol. in cone, adds and electrolytes, sodium hydroxide, potassium hydroxide, HCI, phosphoric acid pH 8.7 (10%) %% act. 

Castner-Kellner cell An electrolytic cell for the production of sodium hydroxide. ... 

Sodium hydroxide is manufactured by electrolysis of concentrated aqueous sodium chloride the other product of the electrolysis, chlorine, is equally important and hence separation of anode and cathode products is necessary. This is achieved either by a diaphragm (for example in the Hooker electrolytic cell) or by using a mercury cathode which takes up the sodium formed at the cathode as an amalgam (the Kellner-Solvay ceW). The amalgam, after removal from the electrolyte cell, is treated with water to give sodium hydroxide and mercury. The mercury cell is more costly to operate but gives a purer product. 

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. 

Sodium Hydroxide. Before World War 1, nearly all sodium hydroxide [1310-93-2], NaOH, was produced by the reaction of soda ash and lime. The subsequent rapid development of electrolytic production processes, resulting from growing demand for chlorine, effectively shut down the old lime—soda plants except in Eastern Europe, the USSR, India, and China. Recent changes in chlorine consumption have reduced demand, putting pressure on the price and availabiHty of caustic soda (NaOH). Because this trend is expected to continue, there is renewed interest in the lime—soda production process. EMC operates a 50,000 t/yr caustic soda plant that uses this technology at Green River it came onstream in mid-1990. Other U.S. soda ash producers have aimounced plans to constmct similar plants (1,5). 

Electrolytic Preparation of Chlorine and Caustic Soda. The preparation of chlorine [7782-50-5] and caustic soda [1310-73-2] is an important use for mercury metal. Since 1989, chlor—alkali production has been responsible for the largest use for mercury in the United States. In this process, mercury is used as a flowing cathode in an electrolytic cell into which a sodium chloride [7647-14-5] solution (brine) is introduced. This brine is then subjected to an electric current, and the aqueous solution of sodium chloride flows between the anode and the mercury, releasing chlorine gas at the anode. The sodium ions form an amalgam with the mercury cathode. Water is added to the amalgam to remove the sodium [7440-23-5] forming hydrogen [1333-74-0] and sodium hydroxide and relatively pure mercury metal, which is recycled into the cell (see Alkali and chlorine products). 

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). 

Electrolysis of Fused Sodium Hydroxide. The first successful electrolytic production of sodium was achieved with the Castner cell (2) ... 

Sodium was made from amalgam ia Germany duriag World War II (68). The only other commercial appHcation appears to be the Tekkosha process (74—76). In this method, preheated amalgam from a chlor—alkali cell is suppHed as anode to a second cell operating at 220—240°C. This cell has an electrolyte of fused sodium hydroxide, sodium iodide, and sodium cyanide and an iron cathode. Operating conditions are given ia Table 6. 

Diacetone-L-sorbose (DAS) is oxidized at elevated temperatures in dilute sodium hydroxide in the presence of a catalyst (nickel chloride for bleach or palladium on carbon for air) or by electrolytic methods. After completion of the reaction, the mixture is worked up by acidification to 2,3 4,6-bis-0-isoptopyhdene-2-oxo-L-gulonic acid (2,3 4,6-diacetone-2-keto-L-gulonic acid) (DAG), which is isolated through filtration, washing, and drying. With sodium hypochlorite/nickel chloride, the reported DAG yields ate >90% (65). The oxidation with air has been reported, and a practical process was developed with palladium—carbon or platinum—carbon as catalyst (66,67). The electrolytic oxidation with nickel salts as the catalyst has also... 

This reaction is accelerated by iacreased temperature, iacreased electrolyte concentration, and by the use of sodium hydroxide rather than potassium hydroxide ia the electrolyte. It is beheved that the presence of lithium and sulfur ia the electrode suppress this problem. Generally, if the cell temperature is held below 50°C, the oxidation and/or solubiUty of iron is not a problem under normal cell operating conditions. 

Dithionites. Although the free-dithionous acid, H2S2O4, has never been isolated, the salts of the acid, in particular zinc [7779-86-4] and sodium dithionite [7775-14-6] have been prepared and are widely used as industrial reducing agents. The dithionite salts can be prepared by the reaction of sodium formate with sodium hydroxide and sulfur dioxide or by the reduction of sulfites, bisulfites, and sulfur dioxide with metallic substances such as zinc, iron, or zinc or sodium amalgams, or by electrolytic reduction (147). 

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