ELECTROLYSIS OF SODIUM THROUGH GLASS
( 4 the^ Ed,
Remtten jrom: D. K. Alpern, THE JOVRNLL, $4, 289-90 (1957) by F. B Dutton Checked by: Joqeph E. Bowles, Oak R~dgeI n ~ t ~ t uoft eNuclear Studies PREPARATION
Assemble a 25 watt tubular electric lamp, socket, iron wire gauze, and provision for connection to 110 v ac power source as shown in diagram. Provide a 250 ml beaker containing melted sodium nitrate and burner to maintain temperature just above the melting point (308'C) as shown. DEMONSTRATION
Lower lighted bulb and iron gauze assembly into molten salt. Maintain temperature just high enough so the surface of the molten salt does not freeze (ca. 350°C) Sodium metal will be deposited on the inside of the bulb at the upper cooler region. CAUTION
Care should he taken to use clcan equipment and materials. Fused NaN03is a vigorous oxidizing agent. Avoid contact with combustible material. Operate over a fireproof table snrftm. REMARKS
The bulb containing a sodium mirror may become a permanent demonstration item to show students the appearance of a clean sodium surface. dc may be used in which case the Fe anode must be connected to the positive lamp terminal, This is a versat.ile demonstration which may be used in connection with discussion of electron emission from a hot filament, rectification, Faraday's lav,, the structure and condnctivity of glass, photoelectric devices, and the commercial production of metals from fused salts-see reference given as the wurw of this demonstration.
El J m n n d of C h e m < d E d u a G m
EFFECT OF CHLORIDE IONON PRECIPITATION OF CADMIUM SULFIDE
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Submttted by: T .\. OJ1)onnell, The University of Melbourne, Australia Checked by: R. B. Escue, North Texas State College, Denton, Texas.
PREPARATION Prepare a suspension of CdS hy adding 1 ml 1 M Cd(NOJ2 solution and 5 ml H2S saturated water t o 200 ml of 2 X (1 '74') H2S04. Pour into identical flasks 100 ml volume3 of the suspension. Provide 0 1 mole of solid KaCl (5 85 g) or KC1 (7.46 g) and 0 I mole of correspondmg nitrate (8 3 g or 10 I g) DEMONSTRATION Add 0.1 mole of solid NaCl or KC1 t o one flask and 0 1 mole of corresponding nitrate t o th? other flask. The suspension which has been made 1 M in Cl- ion, will disappear while the other s u ~ p e n 4 o nwill remain unchanged.
REMARKS Frequently v h e n the precipitat.ion of cadmium sulfide from hydrochloric acid solution is discussed the usual treatment is t o deal with the effect of p H on the concentration of free sulfide ion, Only rarely is the effect of the chloride ion discussed quantitatively or qualitat.ively. In each case, the acidity and ionic strengths arc the same, the only difference between the t.~rosystems being t h a t the solution in ~vhichthe cadmium sulfide dissolves is 1 M in chloride ion. The sulfide dissolves hecause ionic equilibria involving entities such as CdC142- must compete with the pH-dependent equilibrinm hetween cadmium ions, sulfide ions, and solid cadmium sulfide.
