Sodium Downs process

Energy Requirements. The energy requirements of several sodium manufacturiag processes are compared ia Table 7 (76). The data contain some ambiguities because of the allocation of energy to the coproduction of chlorine. An iadependent calculation shows a somewhat lower energy consumption for the Downs process (92). 

K.18 The industrial production of sodium metal and chlorine gas makes use of the Downs process, in which molten sodium chloride is electrolyzed (Chapter 12). Write a balanced equation for the production of the two elements from molten sodium chloride. Which element is produced by oxidation and which by reduction ... 

We have already described the refining of copper and the electrolytic extraction of aluminum, magnesium, and fluorine. Another important industrial application of electrolysis is the production of sodium metal by the Downs process, the electrolysis of molten rock salt (Fig. 12.15) ... 

FIGURE 12.15 In the Downs process, molten sodium chloride is electrolyzed with a graphite anode (at which the Cl ions are oxidized to chlorine) and a steel cathode (at which the Na4 ions are reduced to sodium). The sodium and chlorine are kept apart by the hoods surrounding the electrodes. Calcium chloride is present to lower the melting point of sodium chloride to an economical temperature. 

The alkali metals are the most violently reactive of all the metals. They are too easily oxidized to be found in the free state in nature and cannot be extracted from their compounds by ordinary chemical reducing agents. The pure metals are obtained by electrolysis of their molten salts, as in the electrolytic Downs process (Section 12.13) or, in the case of potassium, by exposing molten potassium chloride to sodium vapor ... 

Sodium metal is produced from the electrolysis of molten sodium chloride in the Downs process (Section 12.13). Determine (a) the standard Gibbs free energy of the reaction... 

Sodium chloride is plentiful as rock salt, but the solid does not conduct electricity, because the ions are locked into place. Sodium chloride must be molten for electrolysis to occur. The electrodes in the cell are made of inert materials like carbon, and the cell is designed to keep the sodium and chlorine produced by the electrolysis out of contact with each other and away from air. In a modification of the Downs process, the electrolyte is an aqueous solution of sodium chloride. The products of this chloralkali process are chlorine and aqueous sodium hydroxide. 

Downs process The production of sodium and chlorine by the electrolysis of molten sodium chloride. 

These problems have been overcome by the Downs process, which uses a 58 wt% calcium chloride-42% sodium chloride electrolyte at an operating temperature of 580-590°C. This composition represents a compromise between the melting point of the salt mixture and the sodium purity. The eutectic mixture contains 66.8 wt% CaCl2 and 33.2 wt% NaCl and melts at 505°C. Increasing CaCl2 content reduces the melting point of the mixture and increases the concentration of calcium in the cathode metal due to the equilibrium... 

In the Downs process, molten sodium chloride is electrolyzed to produce sodium. A valuable byproduct is chlorine. Write equations representing the processes taking place at the anode and at the cathode in the Downs process. 

Sodium, economically much the most important of the alkali metals, is manufactured by the Downs process in which... 

Fig. 10.1 A schematic representation of the electrolysis cell used in the Downs process to produce sodium commercially from NaCl. The products (Na and CI2) must be kept separate from each other to prevent recombination to form NaCl.

Downs process An electrolytic process for making chlorine from fused sodium chloride. The anode is a central piece of graphite, surrounded by a cylindrical steel cathode. A grid and dome between the two keeps the products separate. 

The element was first isolated using an electrolysis technique by Sir Humphrey Davy in 1806. He extracted elemental sodium by passing an electric current through molten sodium hydroxide. These days, large-scale extraction of sodium is carried out using the Downs process, where sodium chloride is molten and then electrolyzed. 

Other applications of electrolysis that students could research include sodium production by electrowinning (the Downs process) (a useful website on this process is detailed in the Other resources section at the end of the chapter). 

For information about sodium production by electrowinning (the Downs process) ... 

Downs process An electrolytic process for making sodium and chlorine from fused sodium chloride. The process takes place in a Downs cell, which has a centrally located graphite anode surrounded by a cylindrical steel cathode. A coaxial steel grid keeps the electrodes and their products separate. Chlorine gas is collected via a cone-shaped dome above the anode, while molten sodium floats on top of the denser electrolyte to be siphoned off via a collecting pipe. 

Sodium occurs widely as NaCl in seawater and as deposits of halite in dried-up lakes etc. (2.6% of the Earth s crust). The element is obtained commercially via the Downs process by electrolysis of NaCl melts in which the melting point is reduced by the addition of calcium chloride sodium is produced at the steel cathode. The metal is extremely reactive, vigorously so with the halogens and also with water, in the latter case to give hydrogen and sodium hydroxide. It is used as a coolant in fast-breeder nuclear reactors. The chemistry of sodium is very similar to that of the other members of group 1. 

Electrolytic processes are widely used to manufacture chemicals. One of the simplest of these is the Downs process for manufacturing liquid sodium. This chemically active metal is used to S5mthesize organic compounds, such as tetraethyl lead once widely used as a gasoline additive, and in many other applications. It is made by passing an electrical current through melted sodium chloride, as shown in Figure 8.9. 

Downs process Aprocess used in the extraction of sodium by the electrolysis of a eutectic mixture of sodium chloride and calcium chloride at580°C. The Downs cell has a central graphite anode and is surrounded by a cylindrical steel anode. Released chlorine is led away through a hood over the anode while molten sodium is formed and collected at the cathode. A small amount of calcium chloride is added, which lowers the melting point and... 

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