Chemical elements
  Sodium
    Isotopes
    Energy
    Preparation
    Applications
    Physical Properties
    Chemical Properties
    PDB 131d-1bli
    PDB 1bph-1d10
    PDB 1d11-1ej2
    PDB 1eja-1gb5
    PDB 1gb6-1goh
    PDB 1gq2-1ikp
    PDB 1ikq-1jz1
    PDB 1jz2-1kvs
    PDB 1kvt-1me8
    PDB 1mg2-1nsz
    PDB 1nta-1oyt
    PDB 1p0s-1qjs
    PDB 1qnj-1s5d
    PDB 1s5e-1tjp
    PDB 1tk6-1uxt
    PDB 1uxu-1vzq
    PDB 1w15-1xc6
    PDB 1xcu-1yf1
    PDB 1ygg-1zko
    PDB 1zkp-2afh
    PDB 2agv-2bhc
    PDB 2bhp-2cc6
    PDB 2cc7-2dec
    PDB 2deg-2ein
    PDB 2eit-2fjb
    PDB 2fld-2gg8
    PDB 2gg9-2h9j
    PDB 2h9k-2ien
    PDB 2ieo-2jih
    PDB 2jin-2omd
    PDB 2omg-2p77
    PDB 2p78-2q68
    PDB 2q69-2qz7
    PDB 2qzi-2v35
    PDB 2v3h-2vwo
    PDB 2vx4-2wig
    PDB 2wij-2x1z
    PDB 2x20-2xmk
    PDB 2xmm-2zfq
    PDB 2zfr-3a6s
    PDB 3a6t-3b1e
    PDB 3b2n-3bos
    PDB 3bov-3ccr
    PDB 3ccs-3d7r
    PDB 3d97-3e3y
    PDB 3e40-3erp
    PDB 3euw-3fgw
    PDB 3fh4-3g3r
    PDB 3g3s-3gxw
    PDB 3gyz-3hwt
    PDB 3hww-3ijp
    PDB 3imm-3k0g
    PDB 3k13-3l7x
    PDB 3l88-3max
    PDB 3mbb-3mr1
    PDB 3mty-3nu3
    PDB 3nu4-3ot1
    PDB 3ow2-3qwc
    PDB 3qx5-3tfr
    PDB 3tfs-3v6o
    PDB 3v72-4ag2
    PDB 4aga-4eae
    PDB 4ecn-4g8t
    PDB 4gdt-8icw
    PDB 8icx-9icy

Sodium Preparation






Davy's original method can be modified by electrolyzing a concentrated solution of the hydroxide in contact with mercury, the resulting sodium-amalgam being decomposed by volatilizing the mercury in an atmosphere of petroleum-vapour.

Castners apparatus
Castner's apparatus for the electrolytic production of sodium
Several electrolytic methods have been employed in the isolation of the metal on the manufacturing scale. Castner's patent is worked by the Castner Kellner Co. at Wallsend-on-Tyne. It depends on the electrolysis of fused sodium hydroxide at about 330° C. The fusion is carried out in a gas-fired (G) iron furnace-pan (P), surrounded by brickwork (not shown in the figure). The metallic negative electrode ( - E) is introduced through the bottom of the pan, and its lower part is surrounded by a seal of solid sodium hydroxide (H). The positive electrode (+ E) encircles the upper part of the negative electrode, but is separated from it by a diaphragm consisting of a cylinder of wire- gauze (D) attached to the bottom of the chamber (C). Being specifically lighter than the electrolyte, the liberated sodium (S) rises to the surface. It is directed by the diaphragm (D) into the tubular iron chamber (C) placed over the negative electrode (-E), and is collected by means of ladles perforated to allow the molten hydroxide to drain off. The gas liberated escapes at the opening (O). The periodic addition of fresh sodium hydroxide enables the process to be carried on continuously. A current of 1000-1200 amperes at 4-5 volts is employed, and serves to maintain the temperature after fusion is complete. The yield of sodium is between 40 and 50 per cent, of the theoretical amount.

In another electrolytic method formerly worked commercially, fused sodium chloride was employed as electrolyte. There are several practical difficulties to be overcome in carrying on this process, due partly to the corrosive nature of the chlorine liberated, and partly to the tendency to form the so-called subchloride of sodium. Either the formation of this subchloride must be prevented; or, if produced, it must not be permitted to regenerate sodium chloride by interaction with the chlorine evolved at the anode. The chlorine can be removed by contact at the anode with a heavy metal, such as lead, copper, or silver. Lowering the temperature of fusion by admixture with chloride of potassium or of an alkaline-earth-metal, or with sodium fluoride, prevents the formation of the subchloride.

Electrolytic processes are gradually displacing the older chemical methods of isolating sodium dependent on the reduction of the carbonate or hydroxide with charcoal or iron. On a small scale, magnesium can be employed as reducer. A laboratory method is the reduction of the peroxide with wood-charcoal, coke, graphite, or calcium carbide -

3Na2O2+2C = 2Na2CO3+2Na;
7Na2O2+2CaC2=2CaO + 4Na2CO3+6Na.

Hydrogen is a usual impurity in metallic sodium, and is evolved when the metal reacts with mercury. It can be removed by prolonged heating in vacuum.


© Copyright 2008-2012 by atomistry.com